Oracle® Text

Application Developer's Guide

12c Release 1 (12.1)

E41398-07

May 2015

Provides information for building applications with Oracle Text.

Oracle Text Application Developer's Guide, 12c Release 1 (12.1)

E41398-07

Copyright © 2001, 2015, Oracle and/or its affiliates. All rights reserved.

Primary Author: Cathy Shea

Contributors: Drew Adams, Edwin Balthes, Eric Belden, Rajesh Bhatiya, Aleksandra Czarlinska, Mohammad Faisal, Roger Ford, Rahul Kadwe, George Krupka, Paul Lane, Colin McGregor, Padmaja Potineni, Yiming Qi, Sanoop Sethumadhavan, Asha Tarachandani, Gaurav Yadav

This software and related documentation are provided under a license agreement containing restrictions on use and disclosure and are protected by intellectual property laws. Except as expressly permitted in your license agreement or allowed by law, you may not use, copy, reproduce, translate, broadcast, modify, license, transmit, distribute, exhibit, perform, publish, or display any part, in any form, or by any means. Reverse engineering, disassembly, or decompilation of this software, unless required by law for interoperability, is prohibited.

The information contained herein is subject to change without notice and is not warranted to be error-free. If you find any errors, please report them to us in writing.

If this is software or related documentation that is delivered to the U.S. Government or anyone licensing it on behalf of the U.S. Government, the following notice is applicable:

U.S. GOVERNMENT END USERS: Oracle programs, including any operating system, integrated software, any programs installed on the hardware, and/or documentation, delivered to U.S. Government end users are "commercial computer software" pursuant to the applicable Federal Acquisition Regulation and agency-specific supplemental regulations. As such, use, duplication, disclosure, modification, and adaptation of the programs, including any operating system, integrated software, any programs installed on the hardware, and/or documentation, shall be subject to license terms and license restrictions applicable to the programs. No other rights are granted to the U.S. Government.

This software or hardware is developed for general use in a variety of information management applications. It is not developed or intended for use in any inherently dangerous applications, including applications that may create a risk of personal injury. If you use this software or hardware in dangerous applications, then you shall be responsible to take all appropriate fail-safe, backup, redundancy, and other measures to ensure its safe use. Oracle Corporation and its affiliates disclaim any liability for any damages caused by use of this software or hardware in dangerous applications.

Oracle and Java are registered trademarks of Oracle and/or its affiliates. Other names may be trademarks of their respective owners.

Intel and Intel Xeon are trademarks or registered trademarks of Intel Corporation. All SPARC trademarks are used under license and are trademarks or registered trademarks of SPARC International, Inc. AMD, Opteron, the AMD logo, and the AMD Opteron logo are trademarks or registered trademarks of Advanced Micro Devices. UNIX is a registered trademark of The Open Group.

This software or hardware and documentation may provide access to or information on content, products, and services from third parties. Oracle Corporation and its affiliates are not responsible for and expressly disclaim all warranties of any kind with respect to third-party content, products, and services. Oracle Corporation and its affiliates will not be responsible for any loss, costs, or damages incurred due to your access to or use of third-party content, products, or services.

Contents

Preface

- Audience

- Documentation Accessibility

- Related Documents

- Conventions

Changes in This Release for Oracle Text Application Developer's Guide

- Changes in Oracle Text 12c Release 1 (12.1)

- New Features

- Deprecated Features

- Desupported Features

1 Understanding Oracle Text Application Development

- Introduction to Oracle Text

- Document Collection Applications

- About Document Collection Applications

- Flowchart of Text Query Application

- Catalog Information Applications

- About Catalog Information Applications

- Flowchart for Catalog Query Application

- Document Classification Applications

- XML Search Applications

- The CONTAINS Operator with XML Search Applications

- Combining Oracle Text Features with Oracle XML DB (XML Search Index)

2 Getting Started with Oracle Text

- Overview of Getting Started with Oracle Text

- Creating an Oracle Text User

- Query Application Quick Tour

- Creating the Text Table

- Using SQL*Loader to Load the Table

- Catalog Application Quick Tour

- Creating the Table

- Using SQL*Loader to Load the Table

- Classification Application Quick Tour

- About Classification of a Document

- Steps for Creating a Classification Application

3 Indexing with Oracle Text

- About Oracle Text Indexes

- Types of Oracle Text Indexes

- Structure of the Oracle Text CONTEXT Index

- The Oracle Text Indexing Process

- Partitioned Tables and Indexes

- Creating an Index Online

- Parallel Indexing

- Indexing and Views

- Considerations for Oracle Text Indexing

- Location of Text

- Document Formats and Filtering

- Bypassing Rows for Indexing

- Document Character Set

- Document Language

- Indexing Special Characters

- Case-Sensitive Indexing and Querying

- Document Services Procedures Performance and Forward Index

- Language-Specific Features

- About Entity Extraction and CTX_ENTITY

- Fuzzy Matching and Stemming

- Better Wildcard Query Performance

- Document Section Searching

- Stopwords and Stopthemes

- Index Performance

- Query Performance and Storage of Large Object (LOB) Columns

- Mixed Query Performance

- Creating Oracle Text Indexes

- Summary of Procedure for Creating a Text Index

- Creating Preferences

- Creating Section Groups for Section Searching

- Using Stopwords and Stoplists

- Creating a CONTEXT Index

- Creating a CTXCAT Index

- Creating a CTXRULE Index

- Maintaining Oracle Text Indexes

- Viewing Index Errors

- Dropping an Index

- Resuming Failed Index

- Re-creating an Index

- Rebuilding an Index

- Dropping a Preference

- Managing DML Operations for a CONTEXT Index

- Viewing Pending DML

- Synchronizing the Index

- Optimizing the Index

4 Querying with Oracle Text

- Overview of Queries

- Querying with CONTAINS

- Querying with CATSEARCH

- Querying with MATCHES

- Word and Phrase Queries

- Querying Stopwords

- ABOUT Queries and Themes

- Query Expressions

- Case-Sensitive Searching

- Query Feedback

- Query Explain Plan

- Using a Thesaurus in Queries

- About Document Section Searching

- Using Query Templates

- Query Rewrite

- Query Relaxation

- Query Language

- Ordering By SDATA Sections

- Alternative and User-defined Scoring

- Alternative Grammar

- Query Analysis

- Other Query Features

- The CONTEXT Grammar

- ABOUT Query

- Logical Operators

- Section Searching and HTML and XML

- Proximity Queries with NEAR and NEAR_ACCUM Operators

- Fuzzy, Stem, Soundex, Wildcard and Thesaurus Expansion Operators

- Using CTXCAT Grammar

- Stored Query Expressions

- Calling PL/SQL Functions in CONTAINS

- Optimizing for Response Time

- Counting Hits

- Using DEFINESCORE and DEFINEMERGE for User-defined Scoring

- The CTXCAT Grammar

5 Presenting Documents in Oracle Text

- Highlighting Query Terms

- Text highlighting

- Theme Highlighting

- CTX_DOC Highlighting Procedures

- Obtaining Part-of-Speech Information for a Document

- Obtaining Lists of Themes, Gists, and Theme Summaries

- Lists of Themes

- Gist and Theme Summary

- Document Presentation and Highlighting

- Highlighting Example

- Document List of Themes Example

- Gist Example

6 Classifying Documents in Oracle Text

- Overview of Document Classification

- Classification Applications

- Classification Solutions

- Rule-Based Classification

- Rule-based Classification Example

- CTXRULE Parameters and Limitations

- Supervised Classification

- Decision Tree Supervised Classification

- Decision Tree Supervised Classification Example

- SVM-Based Supervised Classification

- SVM-Based Supervised Classification Example

- Unsupervised Classification (Clustering)

- Unsupervised Classification (Clustering) Example

7 Tuning Oracle Text

- Optimizing Queries with Statistics

- Collecting Statistics

- Query Optimization with Statistics Example

- Re-Collecting Statistics

- Deleting Statistics

- Optimizing Queries for Response Time

- Other Factors that Influence Query Response Time

- Improved Response Time with FIRST_ROWS(n) Hint for ORDER BY Queries

- Improved Response Time Using the DOMAIN_INDEX_SORT Hint

- Improved Response Time using Local Partitioned CONTEXT Index

- Improved Response Time with Local Partitioned Index for Order by Score

- Improved Response Time with Query Filter Cache

- Improved Response Time using BIG_IO Option of CONTEXT Index

- Improved Response Time using SEPARATE_OFFSETS Option of CONTEXT Index

- Improved Response Time using STAGE_ITAB Option of CONTEXT Index

- Optimizing Queries for Throughput

- CHOOSE and ALL ROWS Modes

- FIRST_ROWS(n) Mode

- Composite Domain Index (CDI) in Oracle Text

- Performance Tuning with CDI

- Solving Index and Query Bottlenecks Using Tracing

- Using Parallel Queries

- Parallel Queries on a Local Context Index

- Parallelizing Queries Across Oracle RAC Nodes

- Tuning Queries with Blocking Operations

- Frequently Asked Questions About Query Performance

- What is Query Performance?

- What is the fastest type of text query?

- Should I collect statistics on my tables?

- How does the size of my data affect queries?

- How does the format of my data affect queries?

- What is a functional versus an indexed lookup?

- What tables are involved in queries?

- Does sorting the results slow a text-only query?

- How do I make an ORDER BY score query faster?

- Which memory settings affect querying?

- Does out-of-line LOB storage of wide base table columns improve performance?

- How can I make a CONTAINS query on more than one column faster?

- Is it OK to have many expansions in a query?

- How can local partition indexes help?

- Should I query in parallel?

- Should I index themes?

- When should I use a CTXCAT index?

- When is a CTXCAT index NOT suitable?

- What optimizer hints are available, and what do they do?

- Frequently Asked Questions About Indexing Performance

- How long should indexing take?

- Which index memory settings should I use?

- How much disk overhead will indexing require?

- How does the format of my data affect indexing?

- Can parallel indexing improve performance?

- How can I improve index performance for creating local partitioned index?

- How can I tell how much indexing has completed?

- Frequently Asked Questions About Updating the Index

- How often should I index new or updated records?

- How can I tell when my indexes are getting fragmented?

- Does memory allocation affect index synchronization?

8 Searching Document Sections in Oracle Text

- About Oracle Text Document Section Searching

- Enabling Oracle Text Section Searching

- Oracle Text Section Types

- Oracle Text Section Attributes

- HTML Section Searching with Oracle Text

- Creating HTML Sections

- Searching HTML Meta Tags

- XML Section Searching with Oracle Text

- Automatic Sectioning

- Attribute Searching

- Creating Document Type Sensitive Sections

- Path Section Searching

9 Using Oracle Text Name Search

- Overview of Name Search

- Examples of Using Name Search

10 Working With a Thesaurus in Oracle Text

- Overview of Oracle Text Thesaurus Features

- Oracle Text Thesaurus Creation and Maintenance

- Using a Case-sensitive Thesaurus

- Using a Case-insensitive Thesaurus

- Default Thesaurus

- Supplied Thesaurus

- Defining Terms in a Thesaurus

- Defining Synonyms

- Defining Hierarchical Relations

- Using a Thesaurus in a Query Application

- Loading a Custom Thesaurus and Issuing Thesaurus-based Queries

- Augmenting Knowledge Base with Custom Thesaurus

- About the Supplied Knowledge Base

- Adding a Language-Specific Knowledge Base

- Limitations for Adding Knowledge Bases

11 Using XML Query Result Set Interface

- Overview of the XML Query Result Set Interface

- Using the XML Query Result Set Interface

- Creating XML-Only Applications with Oracle Text

- Example of a Result Set Descriptor

12 Administering Oracle Text

- Oracle Text Users and Roles

- CTXSYS User

- CTXAPP Role

- Granting Roles and Privileges to Users

- DML Queue

- The CTX_OUTPUT Package

- The CTX_REPORT Package

- Text Manager in Oracle Enterprise Manager

- Using Text Manager

- Viewing General Information for a Text Index

- Checking Text Index Health

- Servers and Indexing

- Database Feature Usage Tracking in Oracle Enterprise Manager

- Oracle Text on Oracle Real Application Clusters

13 Migrating Oracle Text Applications

- Oracle Text and Rolling Upgrade with Logical Standby

- CTX_DDL PL/SQL Procedures

- CTX_OUTPUT PL/SQL Procedures

- CTX_DOC PL/SQL Procedures

- About Migrating to Oracle Text 12c Release 1 (12.1)

- About Migrating to Oracle Text 11g Release 2 (11.2)

- About Migrating to Oracle Text 11g Release 1 (11.1)

- About Migrating to Oracle Text 10g Release 2 (10.2)

- Filter Comparison (INSO_FILTER versus AUTO_FILTER)

- About Migrating to the AUTO_FILTER Filter Type

A CONTEXT Query Application

- Web Query Application Overview

- The PL/SQL Server Pages (PSP) Web Application

- PSP Web Application Prerequisites

- Building the PSP Web Application

- PSP Web Application Sample Code

- The Java Server Pages (JSP) Web Application

- JSP Web Application Prerequisites

- JSP Web Application Sample Code

B CATSEARCH Query Application

- CATSEARCH Web Query Application Overview

- The JSP Web Application

- Building the JSP Web Application

- JSP Web Application Sample Code

Glossary

Index

Preface

Welcome to Oracle Text Application Developer's Guide. This document provides information for building applications with Oracle Text. This preface contains the following topics:

- Audience

- Documentation Accessibility

- Related Documents

- Conventions

Audience

This document is intended for users who perform the following tasks:

- Develop Oracle Text applications

- Administer Oracle Text installations

To use this document, you need to have experience with the Oracle object relational database management system, SQL, SQL*Plus, and PL/SQL.

Documentation Accessibility

For information about Oracle's commitment to accessibility, visit the Oracle Accessibility Program website at http://www.oracle.com/pls/topic/lookup?ctx=acc&id=docacc.

Access to Oracle Support

Oracle customers have access to electronic support through My Oracle Support. For information, visit http://www.oracle.com/pls/topic/lookup?ctx=acc&id=info or visit http://www.oracle.com/pls/topic/lookup?ctx=acc&id=trs if you are hearing impaired.

Related Documents

For more information about Oracle Text, see:

- Oracle Text Reference

For more information about Oracle Database, see:

- Oracle Database Concepts

- Oracle Database Administrator's Guide

- Oracle Database Utilities

- Oracle Database Performance Tuning Guide

- Oracle Database SQL Tuning Guide

- Oracle Database SQL Language Reference

- Oracle Database Reference

- Oracle Database Development Guide

- Oracle Database Sample Schemas

For more information about PL/SQL, see:

- Oracle Database PL/SQL Language Reference

Conventions

The following text conventions are used in this document:

Convention

Meaning

boldface

Boldface type indicates graphical user interface elements associated with an action, or terms defined in text or the glossary.

italic

Italic type indicates book titles, emphasis, or placeholder variables for which you supply particular values.

monospace

Monospace type indicates commands within a paragraph, URLs, code in examples, text that appears on the screen, or text that you enter.

Changes in This Release for Oracle Text Application Developer's Guide

This preface describes changes in Oracle Text for this release.

Changes in Oracle Text 12c Release 1 (12.1)

The changes in Oracle Text for Oracle Database 12c Release 1 (12.1) are described in the following topics.

- New Features

- Deprecated Features

- Desupported Features

New Features

This section describes the new features introduced in this release for Oracle Text. For a complete list of new features for Oracle Database 12c, see Oracle Database New Features Guide.

- Performance Enhancements

- Snippet Support in Result Set Interface

- Forward Index for Highlighting and Snippet Generation

- XQuery Full-Text

- Automatic Near Real-Time Indexing

- Language Identification

- Document-Level Lexer

- BIGRAM Mode for Japanese VGRAM Lexer

- Pattern Stopclass

- Query Enhancements

- SDATA sections

- Unlimited Number of Field and MDATA Sections

Performance Enhancements

- BIG_IO Large TOKEN_INFO Option
A new wordlist preference, BIG_IO, specifies that TOKEN_INFO should be stored, where possible, in a single large SecureFiles database field rather than using in-line BLOBS limited to 4,000 bytes.

This avoids the need to do many seeks when loading large TOKEN_INFO data items from disk. Sequential I/O is generally much faster than random I/O, thus improving performance.

See "Improved Response Time using BIG_IO Option of CONTEXT Index."

- Separate Offsets
The DOCID list identifies the documents which contain indexed terms and OFFSET identifies the location of those terms within each document.

A new wordlist preference, SEPARATE_OFFSETS, used in conjunction with BIG_IO, will cause the DOCID and OFFSET to be stored in separate locations within the index.

The DOCID list will be much shorter than the previous combined TOKEN_INFO data. It thus reduces the I/O necessary to perform single term queries, AND queries, and other queries where offset (ie word position) information is not needed. Performance is improved for such queries. Queries that do require offset information (for example phrase or near searches) may be slightly slower.

See "Improved Response Time using SEPARATE_OFFSETS Option of CONTEXT Index."

Snippet Support in Result Set Interface

The Result Set Interface in Oracle Database 11g was able to produce the various kinds of data needed for a page of search results all at once, improving performance by sharing overhead. The Result Set Interface could also return data views which were difficult to express in SQL.

To present snippet information along with search results to the end user, multiple iterations were required in Oracle Database 11g. With the approach in Oracle Database 11g, it was necessary to do a search query and iterate through the result to retrieve snippet information on each row.

In Oracle Database 12c Release 1 (12.1), native support of snippet information from the Result Set Interface resolves the previously mentioned issues. The Result Set Descriptor only needs SNIPPET defined if it is required. If defined, the user retrieves the snippet in the result set along with other search results.

This support provides faster, more flexible applications based on the Result Set Interface.

See "CTX_DOC Highlighting Procedures."

Forward Index for Highlighting and Snippet Generation

The forward index feature stores a tokenized and compressed version of the document in the Oracle Text index. This means that features such as highlighting and snippet generation no longer need to access, filter, and tokenize the original document, which is often an expensive process.

See "Document Services Procedures Performance and Forward Index."

XQuery Full-Text

This feature extends Oracle's support for the W3C XQuery specification by adding support for the XQuery full-text extension. This enables customers to perform XML-aware full text searches on XML content stored in the database.

See Oracle XML DB Developer's Guide for more information about the XQuery full-text specification. Also see Oracle Text Reference for information about using CREATE_SECTION_GROUP with CTX_DDL.SET_SEC_GRP_ATTR to set xml_enable to create an Oracle XML Search Index.

Automatic Near Real-Time Indexing

Near real-time indexing allows for frequent synchronization of indexes with heavy DML by maintaining recently changed index information in a new staging index which is designed to remain in memory. Data can be periodically moved from the staging index to the main index by means of a new MERGE mode for index optimization. The new option is turned on using the STAGE_ITAB storage option.

The new staging index table will be relatively small, and easy to cache in memory. When resident in memory, there is virtually no cost to this part of the index being fragmented. By separating the fragmented recent index from the unfragmented main index, performance improves and users are allowed to synchronize their indexes frequently without slowing down query performance. When used with the TRANSACTIONAL and SYNC(ON COMMIT) index parameters, the index will be effectively synchronous.

See "Improved Response Time using STAGE_ITAB Option of CONTEXT Index."

In conjunction with near real-time indexes, automatic management allows for a background task that avoids the need for running optimize merge to move data from the small (normally in-memory) $G table to the larger (normally on-disk) $I table. The automatic management process runs in the background when the system is not in heavy use. Indexes must be registered with the management system if they are to be automatically optimized.

This feature simplifies management and improves performance for near real-time indexes and avoids the risk of a manual optimize merge slowing down the system.

See Oracle Text Reference for information about setting parameters for near real-time indexes.

Language Identification

A new procedure called POLICY_LANGUAGES has been added to the CTX_DOC package. The procedure enables the identification of the language of a section of text.

Applications can identify the language of a document in order to process it in an appropriate manner (for example, to set a LANGUAGE metadata column).

See Oracle Text Reference for more information about language identification.

Document-Level Lexer

The document-level Lexer allows users to define different Lexer and stoplist preferences to different documents in an index. This is an extension of the MULTI_LEXER and MULTI_STOPLIST features, but now the Lexer choice can be independent of language. This feature enables applications to be more flexible. Different types of document or documents from different sources may have Lexer or stopword requirements which differ.

See "Query Language."

BIGRAM Mode for Japanese VGRAM Lexer

Currently, with Japanese VGRAM lexer, certain Japanese queries require wildcard expansion which can be expensive. Oracle now provides a switch to Japanese VGRAM lexer to generate BIGRAM mode only and, therefore, eliminate the need for wildcard queries.

The benefit of this feature is faster query performance on text indexed with the Japanese VGRAM lexer.

See Oracle Text Reference for more information about the Japanese VGRAM Lexer.

Pattern Stopclass

The pattern stopclass enables you to specify regular expressions, and any tokens matching those regular expressions will be considered as stopwords. In other words, they will not be indexed and will not be considered significant in queries. Unwanted strings, for example hexadecimal numbers or identifying codes, can be removed from the index to save space and improve performance.

See Oracle Text Reference for information about ADD_STOPCLASS for using the pattern stopclass.

Query Enhancements

This release introduces the following query enhancements:

- NEAR operator Enhancements and MNOT operator
The NEAR operator has been improved to allow for nested NEAR operators, and to allow for OR constructs within the NEAR operator. These enhancements improve the flexibility for application creation.

Mild Not (MNOT) is a new operator designed to find words that are not part of a phrase. For example, if you want to find references to the city of York, you might want to avoid finding it as part of the phrase New York. Excluding all documents containing New York does not solve this problem, since some documents might reference York and New York. The new MNOT operator makes such semantics possible.

The MNOT operator improves precision and recall of searches by allowing searches for words, but excluding unwanted phrases containing those words.

See Oracle Text Reference for information about MNOT.

See "Proximity Queries with NEAR and NEAR_ACCUM Operators" for information about the NEAR operator.

- Session-Duration SQEs
Stored Query Expressions (SQEs) are a way of saving frequently used query expressions. Session-duration SQEs are not permanently saved but exist only for the current session. This enbables faster performance than permanent SQEs as they are stored in session memory and avoids the clutter that might occur when SQEs are frequently created for short-term use within an application.

See Oracle Text Reference for information on managing SQEs.

- Query Filter Cache
A common scenario in text searching is that a particular set of criteria are used in many queries. For example, you might want to apply a security filter that restricts the results to only those appropriate to a particular user. The query filter cache feature allows you to cache the results of a particular query, or part of a query, then use those results to filter future searches. Conceptually, this is similar to using a Stored Query Expression (SQE), but it provides better performance for queries that have components shared with other queries.

SDATA sections

This release provides the following new features for SDATA sections:

- Updateable SDATA sections
SDATA sections may be updated using a new PL/SQL package, CTX_DDL.UPDATE_SDATA. This package will update the value of an SDATA item without requiring reindexing of all the data in that row.

This feature provides better performance for rapidly mutating metadata. For example, if you want to include stocklevel in text queries, make it an SDATA section. The associated row might include a long data sheet of information that you do not want to re-index every time the stocklevel changes. With this new feature you can update only the SDATA part of the index.

See Oracle Text Reference for information on updatable SDATA sections with UPDATE_SDATA.

- Adding SDATA sections to existing index
SDATA sections can be added to an existing index without needing to completely rebuild the index. The new SDATA sections will be indexed in all documents added or updated after this time. Previously indexed documents are not affected.

Application flexibility and uptime is improved, as indexes can be modified to reflect new business requirements without having to rebuild the index from scratch.

See Oracle Text Reference for details about SDATA sections.

- Ordering by SDATA sections
Query templates now support ordering by one or more SDATA sections. This allows for more flexible application development and faster queries compared to a standard database sort.

See "Ordering By SDATA Sections."

Unlimited Number of Field and MDATA Sections

Previously, you were allowed only 64 field sections. You can now create an almost unlimited number (10,000+) of field sections. Field sections are more efficient than zone sections. Previously, some applications had to use zone sections since there were not enough field sections available. This feature improves the performance of such applications.

The number of MDATA sections allowed is now effectively unlimited. The previous maximum was 100. This feature provides increased application flexibility. There is no longer a need to combine multiple MDATA fields in a single one.

See "Field Section."

See Oracle Text Reference for information about MDATA sections.

Deprecated Features

Some features that are deprecated in this release for Oracle XML Database may affect Oracle Text XML applications. See Oracle Database Upgrade Guide for information on Oracle XML Database deprecations and changes.

Desupported Features

The following Oracle Text features are desupported in this release:

- CTXXPATH is desupported in Oracle Database 12c Release 1 (12.1). This does not affect the CTXCAT index type. Use XMLIndex indexes instead. See Oracle XML DB Developer's Guide for information about XMLIndex.

- ALTER INDEX OPTIMIZE for Text Indexes is desupported in Oracle Database 12c Release 1 (12.1). The ALTER INDEX OPTIMIZE [token index_token | fast | full [maxtime (time | unlimited)] operation is not supported for Oracle Database 12c. To optimize your index, use CTX_DDL.OPTIMIZE_INDEX. See Oracle Text Reference for information about OPTIMIZE_INDEX.

- SYNC [MEMORY memsize] for Text Indexes is desupported in Oracle Database 12c Release 1 (12.1). To synchronize your index, use CTX_DDL.SYNC_INDEX. See Oracle Text Reference for information about SYNC_INDEX.

- The CHARSET_FILTER filter type is desupported in Oracle Database 12c Release 1 (12.1).

See Oracle Database Upgrade Guide for a complete list of desupported features for Oracle Database 12c.

1 Understanding Oracle Text Application Development

Oracle Text enables you to build text query applications and document classification applications.

This chapter discusses the following topics:

- Introduction to Oracle Text

- Document Collection Applications

- Catalog Information Applications

- Document Classification Applications

- XML Search Applications

Introduction to Oracle Text

Oracle Text provides indexing, word and theme searching, and viewing capabilities for text in query applications and document classification applications.

To design an Oracle Text application, first determine the type of queries you expect to run. This enables you to choose the most suitable index for the task.

Oracle Text is used for the following categories of applications:

- Document Collection Applications

- Catalog Information Applications

- Document Classification Applications

- XML Search Applications

Document Collection Applications

A text query application enables users to search document collections, such as Web sites, digital libraries, or document warehouses.

This section contains the following topics.

- About Document Collection Applications

- Flowchart of Text Query Application

About Document Collection Applications

The collection is typically static with no significant change in content after the initial indexing run. Documents can be of any size and of different formats, such as HTML, PDF, or Microsoft Word. These documents are stored in a document table. Searching is enabled by first indexing the document collection.

Queries usually consist of words or phrases. Application users can specify logical combinations of words and phrases using operators such as OR and AND. Other query operations can be used to improve the search results, such as stemming, proximity searching, and wildcarding.

An important factor for this type of application is retrieving documents relevant to a query while retrieving as few non-relevant documents as possible. The most relevant documents must be ranked high in the result list.

The queries for this type of application are best served with a CONTEXT index on your document table. To query this index, the application uses the SQL CONTAINS operator in the WHERE clause of a SELECT statement.

Figure 1-1 Overview of Text Query Application

Flowchart of Text Query Application

A typical text query application on a document collection enables the user to enter a query. The application enters a CONTAINS query and returns a list, called a hitlist, of documents that satisfy the query. The results are usually ranked by relevance. The application enables the user to view one or more documents in the hitlist.

For example, an application might index URLs (HTML files) on the Web and provide query capabilities across the set of indexed URLs. Hitlists returned by the query application are composed of URLs that the user can visit.

Figure 1-2 illustrates the flowchart of how a user interacts with a simple query application:

1. The user enters a query.

2. The application runs a CONTAINS query.

3. The application presents a hitlist.

4. The user selects document from hitlist.

5. The application presents a document to the user for viewing.

Figure 1-2 Flowchart of a query application

Catalog Information Applications

Catalog information consists of inventory type information, such as that of an online book store or auction site.

This section contains the following topics.

- About Catalog Information Applications

- Flowchart for Catalog Query Application

About Catalog Information Applications

The stored catalog information consists of text information, such as book titles, and related structured information, such as price. The information is usually updated regularly to keep the online catalog up to date with the inventory.

Queries are usually a combination of a text component and a structured component. Results are almost always sorted by a structured component, such as date or price. Good response time is always an important factor with this type of query application.

Catalog applications are best served by a CTXCAT index. Query this index with the CATSEARCH operator in the WHERE clause of a SELECT statement.

Figure 1-3 illustrates the relation of the catalog table, its CTXCAT index, and the catalog application that uses the CATSEARCH operator to query the index.

Figure 1-3 A Catalog Query Application

Flowchart for Catalog Query Application

A catalog application enables users to search for specific items in catalogs. For example, an online store application enables users to search for and purchase items in inventory. Typically, the user query consists of a text component that searches across the textual descriptions plus some other ordering criteria, such as price or date.

Figure 1-4 illustrates the flowchart of a catalog query application for an online electronics store.

1. The user enters the query, consisting of a text component (for example, cd player) and a structured component (for example, order by price).

2. The application executes the CATSEARCH query.

3. The application shows the results ordered accordingly.

4. The user browses the results.

5. The user then either enters another query or performs an action, such as purchasing the item.

Figure 1-4 Flowchart of a Catalog Query Application

Document Classification Applications

In a document classification application, an incoming stream or a set of documents is compared to a pre-defined set of rules. When a document matches one or more rules, the application performs some action.

For example, assume there is an incoming stream of news articles. You can define a rule to represent the category of Finance. The rule is essentially one or more queries that select document about the subject of Finance. The rule might have the form 'stocks or bonds or earnings'.

When a document arrives about a Wall Street earnings forecast and satisfies the rules for this category, the application takes an action, such as tagging the document as Finance or e-mailing one or more users.

To create a document classification application, create a table of rules and then create a CTXRULE index. To classify an incoming stream of text, use the MATCHES operator in the WHERE clause of a SELECT statement. See Figure 1-5 for the general flow of a classification application.

Figure 1-5 Overview of a Document Classification Application

XML Search Applications

An XML search application performs searches over XML documents. A regular document search usually searches across a set of documents to return documents that satisfy a text predicate; an XML search often uses the structure of the XML document to restrict the search. Typically, only that part of the document that satisfies the search is returned. For example, instead of finding all purchase orders that contain the word electric, the user might need only purchase orders in which the comment field contains electric.

Oracle Text enables you to perform XML searching using the following approaches:

- The CONTAINS Operator with XML Search Applications

- Combining Oracle Text Features with Oracle XML DB (XML Search Index)

See Also:

Using XML Query Result Set Interface

The CONTAINS Operator with XML Search Applications

The CONTAINS operator is well suited to structured searching, enabling you to perform restrictive searches with the WITHIN, HASPATH, and INPATH operators. If you use a CONTEXT index, then you can also benefit from the following characteristics of Oracle Text searches:

- Searches are token-based, whitespace-normalized

- Hitlists are ranked by relevance

- Case-sensitive searching

- Section searching

- Linguistic features such as stemming and fuzzy searching

- Performance-optimized queries for large document sets

WARNING:

When Oracle Text is manually uninstalled, the DBMS_XDBT package should be dropped. When Oracle Text is manually reinstalled, the DBMS_XDBT package should be created.

Starting with Oracle Database 12c, Oracle XML Database is automatically installed when you install the new Oracle Database software or when you upgrade.

See Also:

"XML Section Searching with Oracle Text"

Combining Oracle Text Features with Oracle XML DB (XML Search Index)

You can combine the features of Oracle Text and Oracle XML DB to create an XML Search Index for applications where you want to do a full-text retrieval, leveraging the XML structure by entering queries such as "find all nodes that contain the word Pentium." Oracle Database 12c extends Oracle's support for the W3C XQuery specification by adding support for the XQuery full-text extension, which enables you to perform XML-aware full-text searches on XML content stored in the database.

The following topics explain how to use Oracle XML DB with Oracle Text applications:

- Using the xml_enable Method for an XML Search Index

- Using the Text-on-XML Method

- Indexing JSON Data

See Also:

- "XML Section Searching with Oracle Text"

- Oracle Text Reference for information about the xml_enable variable of SET_SEC_GRP_ATTR to enable XML awareness

- Oracle XML DB Developer's Guide for more information about XML full-text indexing and XML Search Index

Using the xml_enable Method for an XML Search Index

An XML Search Index is an XML-enabled Oracle Text index (CTXSYS.CONTEXT). This index type supports IR-style searching and structured searching in one unified index. XML Search Index also stores a Binary PDOM internally within an Oracle Text table, so that XML operations can be functionally evaluated over the Binary PDOM. This XML Search Index is supported for XMLTYPE data stores. XMLEXISTS is seamlessly rewritten to a CONTAINS in the presence of such an XML Search Index.

When an XML Search Index is created, a Binary PDOM of the XML document is materialized in an internal table of Oracle Text. Post evaluation from the Text index will be redirected to go against the PDOM stored in this internal table.

See Also:

Oracle Text Reference for information on xml_enable variable of SET_SEC_GRP_ATTR to enable XML awareness for XML Search Index

The following example creates an Oracle XML Search Index:

exec
CTX_DDL.CREATE_SECTION_GROUP('secgroup','PATH_SECTION_GROUP');
exec
CTX_DDL.SET_SEC_GRP_ATTR('secgroup','xml_enable','t');
CREATE INDEX po_ctx_idx on T(X) indextype is ctxsys.context
parameters (‘section group SECGROUP');

Using the Text-on-XML Method

With Oracle Text, you can create a CONTEXT index on a column that contains XML data. The column type can be XMLType, but it can also be any supported type provided you use the correct index preference for XML data.

With the Text-on-XML method, use the standard CONTAINS query and add a structured constraint to limit the scope of a search to a particular section, field, tag, or attribute. This amounts to specifying the structure inside text operators, such as WITHIN, HASPATH, and INPATH.

For example, set up your CONTEXT index to create sections with XML documents. Consider the following XML document that defines a purchase order.

<?xml version="1.0"?>
<PURCHASEORDER pono="1">
<PNAME>Po_1</PNAME>
<CUSTNAME>John</CUSTNAME>
<SHIPADDR>
<STREET>1033 Main Street</STREET>
<CITY>Sunnyvalue</CITY>
<STATE>CA</STATE>
</SHIPADDR>
<ITEMS>
<ITEM>
<ITEM_NAME> Dell Computer </ITEM_NAME>
<DESC> Pentium 2.0 Ghz 500MB RAM  </DESC>
</ITEM>
<ITEM>
<ITEM_NAME> Norelco R100 </ITEM_NAME>
<DESC>Electric Razor </DESC>
</ITEM>
</ITEMS>
</PURCHASEORDER>

To query all purchase orders that contain Pentium within the item description section, use the WITHIN operator:

SELECT id from po_tab where CONTAINS( doc, 'Pentium WITHIN desc') > 0;

Specify more complex criteria with XPATH expressions using the INPATH operator:

SELECT id from po_tab where  CONTAINS(doc, 'Pentium INPATH (/purchaseOrder/items/item/desc') > 0;

Indexing JSON Data

JavaScript Object Notation (JSON) is a language-independent data format that is used for serializing structured data and exchanging this data over a network, typically between a server and web applications. JSON provides a text-based way of representing JavaScript object literals, arrays, and scalar data. For more information, see the chapter about JSON in Oracle XML DB Developer's Guide.

See Also:

Oracle Text Reference for information about the json_enable variable of SET_SEC_GRP_ATTR to enable JSON awareness for a CONTEXT index

2 Getting Started with Oracle Text

This chapter discuses the following topics:

- Overview of Getting Started with Oracle Text

- Creating an Oracle Text User

- Query Application Quick Tour

- Catalog Application Quick Tour

- Classification Application Quick Tour

Overview of Getting Started with Oracle Text

This chapter provides basic information about how to create an Oracle Text developer user account, and how to build simple text query and catalog applications. It also provides information about basic SQL statements for each type of application to load, index, and query tables.

More complete application examples are given in the Appendices. To learn more about building document classification applications, see Classifying Documents in Oracle Text.

Note:

The SQL> prompt has been omitted in this chapter, in part to improve readability and in part to make it easier for you to cut and paste text.

Creating an Oracle Text User

Before you can create Oracle Text indexes and use Oracle Text PL/SQL packages, you need to create a user with the CTXAPP role. This role enables you to do the following:

- Create and delete Oracle Text indexing preferences

- Use the Oracle Text PL/SQL packages

To create an Oracle Text application developer user, perform the following steps as the system administrator user:

1. Create the user

The following SQL statement creates a user called MYUSER with a password of myuser_password:

CREATE USER myuser IDENTIFIED BY myuser_password;

2. Grant roles to the user

The following SQL statement grants the required roles of RESOURCE, CONNECT, and CTXAPP to MYUSER:

GRANT RESOURCE, CONNECT, CTXAPP TO MYUSER;

3. Grant EXECUTE privileges on CTX PL/SQL package

Oracle Text includes several packages that let you perform actions ranging from synchronizing an Oracle Text index to highlighting documents. For example, the CTX_DDL package includes the SYNC_INDEX procedure, which enables you to synchronize your index. The Oracle Text Reference describes each of these packages in its own chapter.

To call any of these procedures from a stored procedure, your application requires execute privileges on the packages. For example, to grant execute privileges to MYUSER on all Oracle Text packages, enter the following SQL statements:

GRANT EXECUTE ON CTXSYS.CTX_CLS TO myuser;
GRANT EXECUTE ON CTXSYS.CTX_DDL TO myuser;
GRANT EXECUTE ON CTXSYS.CTX_DOC TO myuser;
GRANT EXECUTE ON CTXSYS.CTX_OUTPUT TO myuser;
GRANT EXECUTE ON CTXSYS.CTX_QUERY TO myuser;
GRANT EXECUTE ON CTXSYS.CTX_REPORT TO myuser;
GRANT EXECUTE ON CTXSYS.CTX_THES TO myuser;
GRANT EXECUTE ON CTXSYS.CTX_ULEXER TO myuser;

Note:

These permissions are granted to the CTXAPP role. However, role permissions do not always work in PL/SQL procedures, so it is safest to explicitly grant these permissions to the user as well as giving them the CTXAPP role.

Query Application Quick Tour

In a basic text query application, users enter query words or phrases and expect the application to return a list of documents that best match the query. Such an application involves creating a CONTEXT index and querying it with CONTAINS.

Typically, query applications require a user interface. An example of how to build such a query application using the CONTEXT index type is given in CONTEXT Query Application.

The examples in this section provide the basic SQL statements to load the text table, index the documents, and query the index.

- Creating the Text Table

- Using SQL*Loader to Load the Table

Creating the Text Table

Perform the following steps to create and load documents into a table.

1. Connect as the New User

Before creating any tables, assume the identity of the user you just created.

CONNECT myuser;

2. Create your Text Table

The following example creates a table called docs with two columns, id and text, by using the CREATE TABLE statement. This example makes the id column the primary key. The text column is VARCHAR2.

CREATE TABLE docs (id NUMBER PRIMARY KEY, text VARCHAR2(200));

Note:

Primary keys of the following type are supported:NUMBER, VARCHAR2, DATE, CHAR, VARCHAR, and RAW.

3. Load Documents into Table

Use the SQL INSERT statement to load text to a table.

To populate the docs table, use the INSERT statement as follows:

INSERT INTO docs VALUES(1, '<HTML>California is a state in the US.</HTML>');
INSERT INTO docs VALUES(2, '<HTML>Paris is a city in France.</HTML>');
INSERT INTO docs VALUES(3, '<HTML>France is in Europe.</HTML>');

Using SQL*Loader to Load the Table

You can perform the following steps to optionally load your table in batch with SQL*Loader.

- Step 1 Create the CONTEXT index

- Step 2 Querying Your Table with CONTAINS

- Step 3 Present the Document

- Step 4 Synchronize the Index After Data Manipulation

See Also:

"Building the PSP Web Application" for an example on how to use SQL*Loader to load a text table from a data file

Step 1 Create the CONTEXT index

Index the HTML files by creating a CONTEXT index on the text column as follows. Because you are indexing HTML, this example uses the NULL_FILTER preference type for no filtering and the HTML_SECTION_GROUP type:

CREATE INDEX idx_docs ON docs(text)
INDEXTYPE IS CTXSYS.CONTEXT PARAMETERS
('FILTER CTXSYS.NULL_FILTER SECTION GROUP CTXSYS.HTML_SECTION_GROUP');

Use the NULL_FILTER, because you do not need to filter HTML documents during indexing. However, if you index PDF, Microsoft Word, or other formatted documents, then use the CTXSYS.AUTO_FILTER (the default) as your FILTER preference.

This example also uses the HTML_SECTION_GROUP section group, which is recommended for indexing HTML documents. Using HTML_SECTION_GROUP enables you to search within specific HTML tags and eliminates from the index unwanted markup such as font information.

Step 2 Querying Your Table with CONTAINS

First, set the format of the SELECT statement's output so it is easily readable. Set the width of the text column to 40 characters:

COLUMN text FORMAT a40;

Now query the table with the SELECT statement with CONTAINS. This retrieves the document IDs that satisfy the query. The following query looks for all documents that contain the word France:

SELECT SCORE(1), id, text FROM docs WHERE CONTAINS(text, 'France', 1) > 0;

SCORE(1)         ID TEXT
---------- ---------- ----------------------------------------
4          3 <HTML>France is in Europe.</HTML>
4          2 <HTML>Paris is a city in France.</HTML>

Step 3 Present the Document

In a real application, you might want to present the selected document to the user with query terms highlighted. Oracle Text enables you to mark up documents with the CTX_DOC package.

We can demonstrate HTML document markup with an anonymous PL/SQL block in SQL*Plus. However, in a real application you might present the document in a browser.

This PL/SQL example uses the in-memory version of CTX_DOC.MARKUP to highlight the word France in document 3. It allocates a temporary CLOB (Character Large Object datatype) to store the markup text and reads it back to the standard output. The CLOB is then de-allocated before exiting:

SET SERVEROUTPUT ON;
DECLARE
2  mklob CLOB;
3  amt NUMBER := 40;
4  line VARCHAR2(80);
5  BEGIN
6    CTX_DOC.MARKUP('idx_docs','3','France', mklob);
7    DBMS_LOB.READ(mklob, amt, 1, line);
8    DBMS_OUTPUT.PUT_LINE('FIRST 40 CHARS ARE:'||line);
9    DBMS_LOB.FREETEMPORARY(mklob);
10    END;
11  /
FIRST 40 CHARS ARE:<HTML><<<France>>> is in Europe.</HTML>

PL/SQL procedure successfully completed.

Step 4 Synchronize the Index After Data Manipulation

When you create a CONTEXT index, you need to explicitly synchronize your index to keep it up to date with any inserts, updates, or deletes to the text table.

Oracle Text enables you to do so with the CTX_DDL.SYNC_INDEX procedure.

Add some rows to the docs table:

INSERT INTO docs VALUES(4, '<HTML>Los Angeles is a city in California.</HTML>');
INSERT INTO docs VALUES(5, '<HTML>Mexico City is big.</HTML>');

Because the index is not synchronized, these new rows are not returned with a query on city:

SELECT SCORE(1), id, text FROM docs WHERE CONTAINS(text, 'city', 1) > 0;

SCORE(1)         ID TEXT
---------- ---------- --------------------------------------------------
4          2 <HTML>Paris is a city in France.</HTML>

Therefore, synchronize the index with 2Mb of memory, and rerun the query:

EXEC CTX_DDL.SYNC_INDEX('idx_docs', '2M');

PL/SQL procedure successfully completed.

COLUMN text FORMAT a50;
SELECT SCORE(1), id, text FROM docs WHERE CONTAINS(text, 'city', 1) > 0;

SCORE(1)         ID TEXT
---------- ---------- --------------------------------------------------
4          5 <HTML>Mexico City is big.</HTML>
4          4 <HTML>Los Angeles is a city in California.</HTML>
4          2 <HTML>Paris is a city in France.</HTML>

Catalog Application Quick Tour

The examples in this section provide the basic SQL statements to create a catalog index for an auction site that sells electronic equipment, such as cameras and CD players. New inventory is added everyday and item descriptions, bid dates, and prices must be stored together.

The application requires good response time for mixed queries. The key is to determine what columns users frequently search to create a suitable CTXCAT index. Queries on this type of index are entered with the CATSEARCH operator.

- Creating the Table

- Using SQL*Loader to Load the Table

Note:

Typically, query applications require a user interface. An example of how to build such a query application using the CATSEARCH index type is given in CATSEARCH Query Application .

Creating the Table

Perform the following steps to create and load the table.

1. Connect as the Appropriate User

Connect as the CTXAPP role the user myuser:

CONNECT myuser;

2. Create Your Table

Set up an auction table to store your inventory:

CREATE TABLE auction(
item_id NUMBER,
title VARCHAR2(100),
category_id NUMBER,
price NUMBER,
bid_close DATE);

Figure 2-1 illustrates this table.

3. Populate Your Table

Populate the table with various items, each with an id, title, price and bid_date:

INSERT INTO AUCTION VALUES(1, 'NIKON CAMERA', 1, 400, '24-OCT-2002');
INSERT INTO AUCTION VALUES(2, 'OLYMPUS CAMERA', 1, 300, '25-OCT-2002');
INSERT INTO AUCTION VALUES(3, 'PENTAX CAMERA', 1, 200, '26-OCT-2002');
INSERT INTO AUCTION VALUES(4, 'CANON CAMERA', 1, 250, '27-OCT-2002');

Using SQL*Loader to Load the Table

You can perform the steps in this section to optionally load your table in batch with SQL*Loader.

- Step 1 Determine your Queries

- Step 2 Create the Sub-Index to Order by Price

- Step 3 Create the CTXCAT Index

- Step 4 Querying Your Table with CATSEARCH

- Step 5 Update Your Table

See Also:

"Building the PSP Web Application" for an example on how to use SQL*Loader to load a text table from a data file

Step 1 Determine your Queries

Determine what criteria are likely to be retrieved. In this example, you determine that all queries search the title column for item descriptions, and most queries order by price. When using the CATSEARCH operator later, we'll specify the terms for the text column and the criteria for the structured clause.

Step 2 Create the Sub-Index to Order by Price

For Oracle Text to serve these queries efficiently, we need a sub-index for the price column, because our queries will order by price.

Therefore, create an index set called auction_set and add a sub-index for the price column:

EXEC CTX_DDL.CREATE_INDEX_SET('auction_iset');
EXEC CTX_DDL.ADD_INDEX('auction_iset','price'); /* sub-index A*/

Step 3 Create the CTXCAT Index

Create the combined catalog index on the AUCTION table with CREATE INDEX as follows:

CREATE INDEX auction_titlex ON AUCTION(title) INDEXTYPE IS CTXSYS.CTXCAT PARAMETERS ('index set auction_iset');

Figure 2-1 shows how the CTXCAT index and its sub-index relates to the columns.

Figure 2-1 Auction table schema and CTXCAT index

Step 4 Querying Your Table with CATSEARCH

When you have created the CTXCAT index on the AUCTION table, you can query this index with the CATSEARCH operator.

First set the output format to make the output readable:

COLUMN title FORMAT a40;

Now run the query:

SELECT title, price FROM auction WHERE CATSEARCH(title, 'CAMERA', 'order by price')> 0;

TITLE                PRICE
--------------- ----------
PENTAX CAMERA          200
CANON CAMERA           250
OLYMPUS CAMERA         300
NIKON CAMERA           400

SELECT title, price FROM auction WHERE CATSEARCH(title, 'CAMERA',
'price <= 300')>0;

TITLE                PRICE
--------------- ----------
PENTAX CAMERA          200
CANON CAMERA           250
OLYMPUS CAMERA         300

Step 5 Update Your Table

Update your catalog table by adding new rows. When you do so, the CTXCAT index is automatically synchronized to reflect the change.

For example, add the following new rows to our table and then rerun the query:

INSERT INTO AUCTION VALUES(5, 'FUJI CAMERA', 1, 350, '28-OCT-2002');
INSERT INTO AUCTION VALUES(6, 'SONY CAMERA', 1, 310, '28-OCT-2002');

SELECT title, price FROM auction WHERE CATSEARCH(title, 'CAMERA', 'order by price')> 0;

TITLE                                    PRICE
----------------------------------- ----------
PENTAX CAMERA                              200
CANON CAMERA                               250
OLYMPUS CAMERA                             300
SONY CAMERA                                310
FUJI CAMERA                                350
NIKON CAMERA                               400

6 rows selected.

Note how the added rows show up immediately in the query.

Classification Application Quick Tour

The function of a classification application is to perform some action based on document content. These actions can include assigning a category ID to a document or sending the document to a user. The result is classification of a document.

This section contains the following sections.

- About Classification of a Document

- Steps for Creating a Classification Application

About Classification of a Document

Documents are classified according to predefined rules. These rules select for a category. For instance, a query rule of 'presidential elections' might select documents for a category about politics.

Oracle Text provides several types of classification. One type is simple, or rule-based classification, discussed here, in which you create both document categories and the rules for categorizing documents. With supervised classification, Oracle Text derives the rules from a set of training documents you provide. With clustering, Oracle Text does all the work for you, deriving both rules and categories.

See Also:

"Overview of Document Classification" for more information on classification

To create a simple classification application for document content using Oracle Text, you create rules. Rules are essentially a table of queries that categorize document content. You index these rules in a CTXRULE index. To classify an incoming stream of text, use the MATCHES operator in the WHERE clause of a SELECT statement. See Figure 2-2 for the general flow of a classification application.

Figure 2-2 Overview of a Document Classification Application

Steps for Creating a Classification Application

The following example shows how to classify documents by defining simple categories, creating a CTXRULE index, and using MATCHES, using the CTXAPP role user myuser.

1. Connect As the Appropriate User

Connect as the CTXAPP role user myuser:

CONNECT myuser;

2. Create the Rule Table

We must create a rule table and populate it with query rules. In this example, we create a table called queries. Each row defines a category with an ID, and a rule which is a query string:

CREATE TABLE queries (
query_id      NUMBER,
query_string  VARCHAR2(80)
);

INSERT INTO queries VALUES (1, 'oracle');
INSERT INTO queries VALUES (2, 'larry or ellison');
INSERT INTO queries VALUES (3, 'oracle and text');
INSERT INTO queries VALUES (4, 'market share');

3. Create Your CTXRULE Index

Create a CTXRULE index as follows:

CREATE INDEX queryx ON queries(query_string) INDEXTYPE IS CTXSYS.CTXRULE;

4. Classify with MATCHES

Use the MATCHES operator in the WHERE clause of a SELECT statement to match documents to queries and hence classify.

COLUMN query_string FORMAT a35;
SELECT query_id,query_string FROM queries
WHERE MATCHES(query_string,
'Oracle announced that its market share in databases
increased over the last year.')>0;

QUERY_ID QUERY_STRING
---------- -----------------------------------
1 oracle
4 market share

As shown, the document string matches categories 1 and 4. With this classification you can perform an action, such as writing the document to a specific table or e-mailing a user.

See Also:

Classifying Documents in Oracle Text for more extended classification examples

3 Indexing with Oracle Text

Oracle Text provides several types of indexes, which you create depending on the type of application you want to develop.

This chapter discusses the following topics:

- About Oracle Text Indexes

- Considerations for Oracle Text Indexing

- Creating Oracle Text Indexes

- Maintaining Oracle Text Indexes

- Managing DML Operations for a CONTEXT Index

About Oracle Text Indexes

The discussion of Oracle Text indexes includes the different types of indexes, their structure, the indexing process, and limitations.

The following topics provide information about Oracle Text indexes:

- Types of Oracle Text Indexes

- Structure of the Oracle Text CONTEXT Index

- The Oracle Text Indexing Process

- Partitioned Tables and Indexes

- Creating an Index Online

- Parallel Indexing

- Indexing and Views

Types of Oracle Text Indexes

With Oracle Text, you can create indexes of several types using CREATE INDEX. Table 3-1 describes each index type, its purpose, and the features it supports.

Table 3-1 Oracle Text Index Types

Index Type

Description

Supported Preferences and Parameters

Query Operator

Notes

CONTEXT

Use this index to build a text retrieval application when your text consists of large coherent documents. You can index documents of different formats such as MS Word, HTML or plain text.

You can customize the index in a variety of ways.

This index type requires CTX_DDL.SYNC_INDEX after DML on base table.

All CREATE INDEX preferences and parameters supported except for INDEX SET.

These supported parameters include the index partition clause, and the format, charset, and language columns.

CONTAINS

Grammar is called the CONTEXT grammar, which supports a rich set of operations.

The CTXCAT grammar can be used with query templating.

Supports all documents services and query services.

Supports indexing of partitioned text tables.

Supports FILTER BY and ORDER BY clauses of CREATE INDEX to also index structured column values for more efficient processing of mixed queries.

CTXCAT

Use this index type for better mixed query performance. Typically, with this index type, you index small documents or text fragments. Other columns in the base table, such as item names, prices, and descriptions can be included in the index to improve mixed query performance.

This index type is transactional, automatically updating itself after DML to base table. No CTX_DDL.SYNC_INDEX is necessary.

INDEX SET

LEXER

STOPLIST

STORAGE

WORDLIST (only prefix_index attribute supported for Japanese data)

Format, charset, and language columns not supported.

Table and index partitioning not supported.

CATSEARCH

Grammar is called CTXCAT, which supports logical operations, phrase queries, and wildcarding.

The CONTEXT grammar can be used with query templating.

Theme querying is supported.

This index is larger and takes longer to build than a CONTEXT index.

The size of a CTXCAT index is related to the total amount of text to be indexed, the number of indexes in the index set, and the number of columns indexed. Carefully consider your queries and your resources before adding indexes to the index set.

The CTXCAT index does not support index partitioning, documents services (highlighting, markup, themes, and gists) or query services (explain, query feedback, and browse words.)

CTXRULE

Use CTXRULE index to build a document classification or routing application. This index is created on a table of queries, where the queries define the classification or routing criteria.

See "CTXRULE Parameters and Limitations".

MATCHES

Single documents (plain text, HTML, or XML) can be classified using the MATCHES operator, which turns a document into a set of queries and finds the matching rows in the CTXRULE index.

See Also:

"Creating Oracle Text Indexes"

An Oracle Text index is an Oracle Database domain index. To build your query application, you can create an index of type CONTEXT with a mixture of text and structured data columns, and query it with the CONTAINS operator.

You create an index from a populated text table. In a query application, the table must contain the text or pointers to where the text is stored. Text is usually a collection of documents, but can also be small text fragments.

For better performance for mixed queries, you can create a CONTEXT index with FILTER BY and/or ORDER BY clauses to specify relational columns that will be used in structured criteria of the mixed query. Query this index with the CONTAINS operator.

Use the CTXCAT index type when your application relies heavily on mixed queries to search small documents or descriptive text fragments based on related criteria such as dates or prices. Query this index with the CATSEARCH operator.

To build a document classification application using simple or rule-based classification, create an index of type CTXRULE. This index classifies plain text, HTML, or XML documents using the MATCHES operator. Store your defining query set in the text table you index.

Note:

If you are building a new application that uses XML data, Oracle recommends that instead of using CTXRULE, you use XMLIndex. For information about XMLIndex and indexing XMLType data, see Oracle XML DB Developer's Guide.

Create a text index as a type of extensible index to Oracle Database using standard SQL. This means that an Oracle Text index operates like an Oracle Database index. It has a name by which it is referenced and can be manipulated with standard SQL statements.

The benefits of a creating an Oracle Text index include fast response time for text queries with the CONTAINS, CATSEARCH, and MATCHES Oracle Text operators. These operators query the CONTEXT, CTXCAT, and CTXRULE index types respectively.

Note:

Because a Transparent Data Encryption-enabled column does not support domain indexes, it cannot be used with Oracle Text. However, you can create an Oracle Text index on a column in a table stored in a Transparent Data Encryption-enabled tablespace.

See Also:

"Creating Oracle Text Indexes"

Structure of the Oracle Text CONTEXT Index

Oracle Text indexes text by converting all words into tokens. The general structure of an Oracle Text CONTEXT index is an inverted index where each token contains the list of documents (rows) that contain that token.

For example, after a single initial indexing operation, the word DOG might have an entry as follows:

Word

Appears in Document

DOG

DOC1 DOC3 DOC5

This means that the word DOG is contained in the rows that store documents one, three, and five.

Merged Word and Theme Index

By default in English and French, Oracle Text indexes theme information with word information. You can query theme information with the ABOUT operator. You can optionally enable and disable theme indexing.

See Also:

"Creating Preferences " to learn more about indexing theme information

The Oracle Text Indexing Process

This section describes the Oracle Text indexing process. Initiate the indexing process using the CREATE INDEX statement to create an Oracle Text index of tokens, organized according to the parameters and preferences you specify.

Figure 3-1 shows the indexing process. This process is a data stream that is acted upon by the different indexing objects. Each object corresponds to an indexing preference type or section group you can specify in the parameter string of CREATE INDEX or ALTER INDEX.

Figure 3-1 Oracle Text Indexing Process

Oracle Text processes the data stream with the following objects and engine:

- Datastore Object

- Filter Object

- Sectioner Object

- Lexer Object

- Indexing Engine

Datastore Object

The stream starts with the datastore reading in the documents as they are stored in the system according to your datastore preference. For example, if you have defined your datastore as FILE_DATASTORE, then the stream starts by reading the files from the operating system. You can also store your documents on the Internet or in Oracle Database. Wherever your files reside physically, you must always have a text table in Oracle Database that points to the file.

Filter Object

The stream then passes through the filter. What happens here is determined by your FILTER preference. The stream can be acted upon in one of the following ways:

- No filtering takes place. This happens when you specify the NULL_FILTER preference type or when the value of the format column is IGNORE. Documents that are plain text, HTML, or XML need no filtering.

- Formatted documents (binary) are filtered to marked-up text. This happens when you specify the AUTO_FILTER preference type or when the value of the format column is BINARY.

Sectioner Object

After being filtered, the marked-up text passes through the sectioner that separates the stream into text and section information. Section information includes where sections begin and end in the text stream. The type of sections extracted is determined by your section group type.

The section information is passed directly to the indexing engine which uses it later. The text is passed to the lexer.

Lexer Object

You create a lexer preference using one of the Oracle Text lexer types to specify the language of the text to be indexed. The lexer breaks the text into tokens according to your language. These tokens are usually words. To extract tokens, the lexer uses the parameters as defined in your lexer preference. These parameters include the definitions for the characters that separate tokens such as whitespace, and whether to convert the text to all uppercase or to leave it in mixed case.

When theme indexing is enabled, the lexer analyzes your text to create theme tokens for indexing.

Indexing Engine

The indexing engine creates the inverted index that maps tokens to the documents that contain them. In this phase, Oracle Text uses the stoplist you specify to exclude stopwords or stopthemes from the index. Oracle Text also uses the parameters defined in your WORDLIST preference, which tell the system how to create a prefix index or substring index, if enabled.

Partitioned Tables and Indexes

You can create a partitioned CONTEXT index on a partitioned text table. The table must be partitioned by range. Hash, composite, and list partitions are not supported.

You might create a partitioned text table to partition your data by date. For example, if your application maintains a large library of dated news articles, you can partition your information by month or year. Partitioning simplifies the manageability of large databases, because querying, DML, and backup and recovery can act on a single partition.

On local CONTEXT indexes with multiple table sets, Oracle Text supports the number of partitions supported by Oracle Database.

Note:

The number of partitions supported in Oracle Text is approximately 1024K-1. This limit, which should be more than adequate, is not applicable to a CONTEXT index on partitioned tables.

See Also:

Oracle Database Concepts for more information about partitioning

To query a partitioned table, you use CONTAINS in the WHERE clause of a SELECT statement as you query a regular table. You can query the entire table or a single partition. However, if you are using the ORDER BY SCORE clause, Oracle recommends that you query single partitions unless you include a range predicate that limits the query to a single partition.

Creating an Index Online

When it is not practical to lock up your base table for indexing because of ongoing updates, you can create your index online with the ONLINE parameter of CREATE INDEX. This way an application with heavy DML need not stop updating the base table for indexing.

There are short periods, however, when the base table is locked at the beginning and end of the indexing process.

See Also:

Oracle Text Reference to learn more about creating an index online

Parallel Indexing

Oracle Text supports parallel indexing with CREATE INDEX.

When you enter a parallel indexing statement on a non-partitioned table, Oracle Text splits the base table into temporary partitions, spawns child processes, and assigns a child to a partition. Each child then indexes the rows in its partition. The method of slicing the base table into partitions is determined by Oracle and is not under your direct control. This is true as well for the number of child processes actually spawned, which depends on machine capabilities, system load, your init.ora settings, and other factors. Because of these variables, the actual parallel degree may not match the degree of parallelism requested.

Because indexing is an I/O intensive operation, parallel indexing is most effective in decreasing your indexing time when you have distributed disk access and multiple CPUs. Parallel indexing can only affect the performance of an initial index with CREATE INDEX. It does not affect DML performance with ALTER INDEX, and has minimal impact on query performance.

Because parallel indexing decreases the initial indexing time, it is useful for the following scenarios:

- Data staging, when your product includes an Oracle Text index

- Rapid initial startup of applications based on large data collections

- Application testing, when you need to test different index parameters and schemas while developing your application

See Also:

- "Parallel Queries on a Local Context Index"

- "Frequently Asked Questions About Indexing Performance"

Indexing and Views

Oracle SQL standards do not support creating indexes on views. If you need to index documents whose contents are in different tables, you can create a data storage preference using the USER_DATASTORE object. With this object, you can define a procedure that synthesizes documents from different tables at index time.

See Also:

Oracle Text Reference to learn more about USER_DATASTORE

Oracle Text does support the creation of CONTEXT, CTXCAT, and CTXRULE indexes on materialized views (MVIEW).

Considerations for Oracle Text Indexing

Use the CREATE INDEX statement to create an Oracle Text index. When you create an index and specify no parameter string, an index is created with default parameters. You can create either a CONTEXT, CTXCAT, or CTXRULE index.

This sections contains the following topics:

- Location of Text

- Document Formats and Filtering

- Bypassing Rows for Indexing

- Document Character Set

- Document Language

- Indexing Special Characters

- Case-Sensitive Indexing and Querying

- Document Services Procedures Performance and Forward Index

- Language-Specific Features

- About Entity Extraction and CTX_ENTITY

- Fuzzy Matching and Stemming

- Better Wildcard Query Performance

- Document Section Searching

- Stopwords and Stopthemes

- Index Performance

- Query Performance and Storage of Large Object (LOB) Columns

- Mixed Query Performance

You can also override the defaults and customize your index to suit your query application. The parameters and preference types you use to customize your index with CREATE INDEX fall into the following general categories.

Location of Text

The basic prerequisite for an Oracle Text query application is to have a populated text table. The text table is where you store information about your document collection and is required for indexing.

When you create a CONTEXT index, you can populate rows in your text table with one of the following elements:

- Text information (can be documents or text fragments)

- Path names of documents in your file system

- URLs that specify Web documents

Figure 3-2 illustrates these different methods.

When creating a CTXCAT or CTXRULE index, only the first method shown is supported.

Figure 3-2 Different Ways of Storing Text

By default, the indexing operation expects your document text to be directly loaded in your text table, which is the first method shown previously.

However, when you create a CONTEXT index, you can specify the other ways of identifying your documents such as with filenames or with URLs by using the corresponding data storage indexing preference.

- Supported Column Types

- Storing Text in the Text Table

- Storing File Path Names

- Storing URLs

- Storing Associated Document Information

- Format and Character Set Columns

- Supported Document Formats

- Summary of DATASTORE Types

Supported Column Types

With Oracle Text, you can create a CONTEXT index with columns of type VARCHAR2, CLOB, BLOB, CHAR, BFILE, XMLType, and URIType.

Note:

The column types NCLOB, DATE and NUMBER cannot be indexed.

Storing Text in the Text Table

Oracle Text provides different ways to store text directly in your table.

- CONTEXT Data Storage

- CTXCAT Data Storage

CONTEXT Data Storage

You can store documents in your text table in different ways.

You can store documents in one column using the DIRECT_DATASTORE data storage type or over a number of columns using the MULTI_COLUMN_DATASTORE type. When your text is stored over a number of columns, Oracle Text concatenates the columns into a virtual document for indexing.

You can also create master-detail relationships for your documents, where one document can be stored across a number of rows. To create master-detail index, use the DETAIL_DATASTORE data storage type.

You can also store your text in a nested table using the NESTED_DATASTORE type.

Oracle Text supports the indexing of the XMLType datatype, which you use to store XML documents.

CTXCAT Data Storage

In your text table, you can also store short text fragments such as names, descriptions, and addresses over a number of columns and create a CTXCAT index. A CTXCAT index improves performance for mixed queries.

Storing File Path Names

In your text table, you can store path names to files stored in your file system. When you do so, use the FILE_DATASTORE preference type during indexing. This method of data storage is supported for CONTEXT indexes only.

Storing URLs

You can store URL names to index Web sites. When you do so, use the URL_DATASTORE preference type during indexing. This method of data storage is supported for CONTEXT indexes only.

Storing Associated Document Information

In your text table, you can create additional columns to store structured information that your query application might need, such as primary key, date, description, or author.

Format and Character Set Columns

If your documents are of mixed formats or of mixed character sets, you can create the following additional columns:

- A format column to record the format (TEXT or BINARY) to help filtering during indexing. You can also use the format column to ignore rows for indexing by setting the format column to IGNORE. This is useful for bypassing rows that contain data incompatible with text indexing such as images.

- A character set column to record the document character set for each row.

When you create your index, you must specify the name of the format or character set column in the parameter clause of CREATE INDEX.

For all rows containing the keywords AUTO or AUTOMATIC in character set or language columns, Oracle Text will apply statistical techniques to determine the character set and language respectively of the documents and modify document indexing appropriately.

Supported Document Formats

Because the system can index most document formats including HTML, PDF, Microsoft Word, and plain text, you can load any supported type into the text column.

When you have mixed formats in your text column, you can optionally include a format column to help filtering during indexing. With the format column you can specify whether a document is binary (formatted) or text (non-formatted such as HTML). If you mix HTML and XML documents in 1 index, you might not be able to configure your index to your needs; you cannot prevent stylesheet information from being added to the index.

See Also:

Oracle Text Reference for more information about the supported document formats

Summary of DATASTORE Types

When you index with CREATE INDEX, you specify the location using the datastore preference. Use the appropriate datastore according to your application.

Table 3-2 summarizes the different ways you can store your text with the datastore preference type.

Table 3-2 Summary of DATASTORE Types

Datastore Type

Use When

DIRECT_DATASTORE

Data is stored internally in a text column. Each row is indexed as a single document.

Your text column can be VARCHAR2, CLOB, BLOB, CHAR, or BFILE. XMLType columns are supported for the context index type.

MULTI_COLUMN_DATASTORE

Data is stored in a text table in more than one column. Columns are concatenated to create a virtual document, one document for each row.

DETAIL_DATASTORE

Data is stored internally in a text column. Document consists of one or more rows stored in a text column in a detail table, with header information stored in a master table.

FILE_DATASTORE

Data is stored externally in operating system files. Filenames are stored in the text column, one for each row.

NESTED_DATASTORE

Data is stored in a nested table.

URL_DATASTORE

Data is stored externally in files located on an intranet or the Internet. URLs are stored in the text column.

USER_DATASTORE

Documents are synthesized at index time by a user-defined stored procedure.

Indexing time and document retrieval time will be increased for indexing URLs, because the system must retrieve the document from the network.

Note:

To troubleshoot issues with triggers and MULTI_COLUMN_DATASTORE or USER_DATASTORE, refer to the following article on My Oracle Support: "No pending rows using triggers on Text indexed columns with MULTI_COLUMN_DATASTORE or USER_DATASTORE to bring in the various columns for indexing" (Doc ID 1613741.1)

See Also:

"Datastore Examples"

Document Formats and Filtering

Formatted documents such as Microsoft Word and PDF must be filtered to text to be indexed. The type of filtering the system uses is determined by the FILTER preference type. By default, the system uses the AUTO_FILTER filter type, which automatically detects the format of your documents and filters them to text.

Oracle Text can index most formats. Oracle Text can also index columns that contain documents with mixed formats.

- No Filtering for HTML

- Filtering Mixed-Format Columns

- Custom Filtering

See Also:

Oracle Text Reference for information about AUTO_FILTER supported document and graphics formats

No Filtering for HTML

If you are indexing HTML or plain text files, do not use the AUTO_FILTER type. For best results, use the NULL_FILTER preference type.

See Also:

"NULL_FILTER Example: Indexing HTML Documents"

Filtering Mixed-Format Columns

If you have a mixed-format column such as one that contains Microsoft Word, plain text, and HTML documents, you can bypass filtering for plain text or HTML by including a format column in your text table. In the format column, you tag each row TEXT or BINARY. Rows that are tagged TEXT are not filtered.

For example, you can tag the HTML and plain text rows as TEXT and the Microsoft Word rows as BINARY. You specify the format column in the CREATE INDEX parameter clause.

A third format column type, IGNORE, is provided for when you do not want a document to be indexed at all. This is useful, for example, when you have a mixed-format table that includes plain-text documents in both Japanese and English, but you only want to process the English documents; another example might be that of a mixed-format table that includes both plain-text documents and images. Because IGNORE is implemented at the datastore level, it can be used with all filters.

Custom Filtering

You can create your own custom filter to filter documents for indexing. You can create either an external filter that is executed from the file system or an internal filter as a PL/SQL or Java stored procedure.

For external custom filtering, use the USER_FILTER filter preference type.

For internal filtering, use the PROCEDURE_FILTER filter type.

See Also:

"PROCEDURE_FILTER Example"

Bypassing Rows for Indexing

You can bypass rows in your text table that are not to be indexed, such as rows that contain image data. To do so, create a format column in your table and set it to IGNORE. You name the format column in the parameter clause of CREATE INDEX.

Document Character Set

The indexing engine expects filtered text to be in the database character set. When you use the AUTO_FILTER filter type, formatted documents are converted to text in the database character set.

If your source is text and your document character set is not the database character set, then you can use the AUTO_FILTER filter type to convert your text for indexing.

- Character Set Detection

- Mixed Character Set Columns

Character Set Detection

When the CHARSET column is set to AUTO, the AUTO_FILTER filter detects the character set of the document and converts it from the detected character set to the database character set, if there is a difference.

Mixed Character Set Columns

If your document set contains documents with different character sets, such as JA16EUC and JA16SJIS, you can index the documents provided you create a charset column. You populate this column with the name of the document character set for each row. You name the column in the parameter clause of the CREATE INDEX statement.

Document Language

Oracle Text can index most languages. By default, Oracle Text assumes the language of text to index is the language you specify in your database setup. Depending on the language of your documents, use one of the following lexer types:

Use the BASIC_LEXER preference type to index whitespace-delimited languages such as English, French, German, and Spanish. For some of these languages, you can enable alternate spelling, composite word indexing, and base letter conversion.

Use the MULTI_LEXER preference type for indexing tables containing documents of different languages such as English, German, and Japanese.

Use the USER_LEXER preference type to create your own lexer for indexing a particular language.

Use the WORLD_LEXER preference type for indexing tables containing documents of different languages and to autodetect the languages in the document.

You can also use other lexer types that are designed specifically to tokenize and index Japanese, Chinese, and Korean.

- Language Features Outside BASIC_LEXER

- Indexing Multi-language Columns

See Also:

Oracle Text Reference to learn more about indexing languages and lexer types

Language Features Outside BASIC_LEXER

With the BASIC_LEXER, Japanese, Chinese and Korean lexers, Oracle Text provides a lexing solution for most languages. For other languages, you can create your own lexing solution using the user-defined lexer interface. This interface enables you to create a PL/SQL or Java procedure to process your documents during indexing and querying.

You can also use the user-defined lexer to create your own theme lexing solution or linguistic processing engine.

See Also:

Oracle Text Reference to learn more about the user-defined lexer

Indexing Multi-language Columns

Oracle Text can index text columns that contain documents of different languages, such as a column that contains documents written in English, German, and Japanese. To index a multi-language column, you need a language column in your text table. Use the MULTI_LEXER preference type.

You can also incorporate a multi-language stoplist when you index multi-language columns.

See Also:

"MULTI_LEXER Example: Indexing a Multi-Language Table"

Indexing Special Characters

When you use the BASIC_LEXER preference type, you can specify how non-alphanumeric characters such as hyphens and periods are indexed in relation to the tokens that contain them. For example, you can specify that Oracle Text include or exclude hyphen character (-) when indexing a word such as Web-site.

These characters fall into BASIC_LEXER categories according to the behavior you require during indexing. The way you set the lexer to behave for indexing is the way it behaves for query parsing.

Some of the special characters you can set are as follows:

- Printjoin Characters

- Skipjoin Characters

- Other Characters

Printjoin Characters

Define a non-alphanumeric character as printjoin when you want this character to be included in the token during indexing.

For example, if you want your index to include hyphens and underscore characters, define them as printjoins. This means that words such as web-site are indexed as web-site. A query on website does not find web-site.

See Also:

"BASIC_LEXER Example: Setting Printjoin Characters"

Skipjoin Characters

Define a non-alphanumeric character as a skipjoin when you do not want this character to be indexed with the token that contains it.

For example, with the hyphen (-) character defined as a skipjoin, the word web-site is indexed as website. A query on web-site finds documents containing website and web-site.

Other Characters

Other characters can be specified to control other tokenization behavior such as token separation (startjoins, endjoins, whitespace), punctuation identification (punctuations), number tokenization (numjoins), and word continuation after line-breaks (continuation). These categories of characters have defaults, which you can modify.

See Also:

Oracle Text Reference to learn more about the BASIC_LEXERtype

Case-Sensitive Indexing and Querying

By default, all text tokens are converted to uppercase and then indexed. This results in case-insensitive queries. For example, separate queries on each of the three words cat, CAT, and Cat all return the same documents.

You can change the default and have the index record tokens as they appear in the text. When you create a case-sensitive index, you must specify your queries with exact case to match documents. For example, if a document contains Cat, you must specify your query as Cat to match this document. Specifying cat or CAT does not return the document.

To enable or disable case-sensitive indexing, use the mixed_case attribute of the BASIC_LEXER preference.

See Also:

Oracle Text Reference to learn more about the BASIC_LEXER

Document Services Procedures Performance and Forward Index

Oracle Text uses an inverted index while searching for a word in a document, and then displays the results by calculating the snippet from that document. For calculating the snippet, each document returned as part of the search result is re-indexed. The search operation slows down considerably when the size of a document is very large.

The forward index overcomes the performance problem of very large documents. The forward index uses a mapping table $O that refers to the token offsets in the inverted index table $I. Each token offset is translated into the character offset in the original document, and the text surrounding the character offset is then used to generate the text snippet.

As the forward index does not use in-memory indexing of the documents while calculating the snippet, it provides considerable performance improvement over the inverted index while searching for a word in very large size documents.

The forward index improves the performance of the following procedures of Oracle Text's CTX_DOC package:

- CTX_DOC.SNIPPET

- CTX_DOC.HIGHLIGHT

- CTX_DOC.MARKUP

Enabling Forward Index

The following example enables the forward index feature by setting the forward_index attribute value of the BASIC_STORAGE storage type to TRUE.

exec ctx_ddl.create_preference('mystore', 'BASIC_STORAGE');
exec ctx_ddl.set_attribute('mystore','forward_index','TRUE');

Using Forward Index with Snippets

In some cases, when the forward_index option is used, snippets generated may be slightly different from the snippets generated when the forward_index option is not used. These differences are generally minimal and do not affect snippet quality. These differences are of the type "few extra white spaces" and "newline" as part of the snippet, and when using forward_index.

Using Forward Index with Save Copy

To use the forward index effectively, copies of all the documents should be stored in the $D table, either in the plain text format or the filtered format, depending upon the CTX_DOC package procedure you use. For example, store the document in plain text format when using the SNIPPET procedure, and store it in the filtered format when using the MARKUP or the HIGHLIGHT procedure.

You should use the Save Copy feature of Oracle Text to store the copies of the documents in the $D table. The Save Copy feature can be implemented in Oracle Text by either using the save_copy basic storage attribute or using the save_copy column index parameter.

- Using the save_copy basic storage attribute:
The following example sets the save_copy attribute value of the BASIC_STORAGE storage type to PLAINTEXT. This enables saving a copy of the text document into the $D table while searching for a word in that document.

exec ctx_ddl.create_preference('mystore', 'BASIC_STORAGE');
exec ctx_ddl.set_attribute('mystore','save_copy','PLAINTEXT');

- Using the save_copy column index parameter:
The following example uses the save_copy column index parameter to save the copy of a text document into the $D table.

create table docs(
id       number,
txt      varchar2(64),
save     varchar2(3)
);

insert into docs values(1, 'hello world', 'PLAINTEXT');

create index idx on docs(txt) indextype is ctxsys.context
parameters('save_copy column save');

The create index statement creates the $D table and copies document 1, that is, "hello world", into the $D table.

Note:

You can specify one of the following values for the save_copy attribute/column parameter: PLAINTEXT, FILTERED, or NONE.

- Specifying PLAINTEXT saves the copy of the document in a plain text format in the $D index table. The plain text format is defined as the output format of the sectioner. Specify this value when using the SNIPPET procedure.

- Specifying FILTERED saves the copy of the document in a filtered format in the $D index table. The filtered format is defined as the output format of the filter. Specify this value when using the MARKUP procedure or the HIGHLIGHT procedure.

- Specifying NONE does not save the copy of the document in the $D index table. Specify this value for any of the following scenarios:

- when SNIPPET, MARKUP, or HIGHLIGHT procedure is not used.

- when the indexed column is either VARCHAR2 or CLOB.

Using Forward Index without using Save Copy

There are certain scenarios where you can still take advantage of the forward index performance enhancement without saving the copies of all the documents in the $D table, that is, without using the Save Copy feature. These scenarios are as follows:

- The set of documents contain HTML and plain text: All the documents should be stored in the base table using either the DIRECT_DATASTORE or the MULTI_COLUMN_DATASTORE datastore type.

- The set of documents contain HTML, plain text, and binary: All the documents should be stored in the base table using the DIRECT_DATASTORE datastore type, and only the binary documents should be stored in the $D table in the filtered format.

Using Save Copy without using Forward Index

The Save Copy feature improves the performance of the following procedures of the CTX_DOC package, even if the forward index feature is not enabled:

- CTX_DOC.FILTER

- CTX_DOC.GIST

- CTX_DOC.THEMES

- CTX_DOC.TOKENS

See Also:

Oracle Text Reference for information about the forward_index parameter clause of the BASIC_STORAGE indexing type

Language-Specific Features

You can enable the following language-specific features at index time:

- Indexing Themes

- Base-Letter Conversion for Characters with Diacritical Marks

- Alternate Spelling

- Composite Words

- Korean_ Japanese_ and Chinese Indexing

Indexing Themes

For English and French, you can index document theme information. A document theme is a concept that is sufficiently developed in the document. Themes can be queried with the ABOUT operator.

You can index theme information in other languages provided you have loaded and compiled a knowledge base for the language.

By default themes are indexed in English and French. You can enable and disable theme indexing with the index_themes attribute of the BASIC_LEXER preference type.

See Also:

- Oracle Text Reference to learn more about the BASIC_LEXER

- "ABOUT Queries and Themes"

Base-Letter Conversion for Characters with Diacritical Marks

Some languages contain characters with diacritical marks such as tildes, umlauts, and accents. When your indexing operation converts words containing diacritical marks to their base letter form, queries need not contain diacritical marks to score matches. For example, in Spanish with a base-letter index, a query of energía matches energía and energia in the index.

However, with base-letter indexing disabled, a query of energía matches only energía.

You can enable and disable base-letter indexing for your language with the base_letter attribute of the BASIC_LEXER preference type.

See Also:

Oracle Text Reference to learn more about the BASIC_LEXER

Alternate Spelling

Languages such as German, Danish, and Swedish contain words that have more than one accepted spelling. For instance, in German, ae can be substituted for ä. The ae character pair is known as the alternate form.

By default, Oracle Text indexes words in their alternate forms for these languages. Query terms are also converted to their alternate forms. The result is that these words can be queried with either spelling.

You can enable and disable alternate spelling for your language using the alternate_spelling attribute in the BASIC_LEXER preference type.

See Also:

Oracle Text Reference to learn more about the BASIC_LEXER

Composite Words

German and Dutch text contain composite words. By default, Oracle Text creates composite indexes for these languages. The result is that a query on a term returns words that contain the term as a sub-composite.

For example, in German, a query on the term Bahnhof (train station) returns documents that contain Bahnhof or any word containing Bahnhof as a sub-composite, such as Hauptbahnhof, Nordbahnhof, or Ostbahnhof.

You can enable and disable the creation of composite indexes with the composite attribute of the BASIC_LEXER preference.

See Also:

Oracle Text Reference to learn more about the BASIC_LEXER

Korean, Japanese, and Chinese Indexing

Index these languages with specific lexers:

Table 3-3 Lexers for Asian Languages

Language

Lexer

Korean

KOREAN_MORPH_LEXER

Japanese

JAPANESE_LEXER, JAPANESE_VGRAM_LEXER

Chinese

CHINESE_LEXER,CHINESE_VGRAM_LEXER

These lexers have their own sets of attributes to control indexing.

See Also:

Oracle Text Reference to learn more about these lexers

About Entity Extraction and CTX_ENTITY

Entity extraction is the capability to identify, and extract, named entities within a text. Entities are mainly nouns and noun phrases. They include names, places, times, coded strings (such as phone numbers and zip codes), percentages, monetary amounts and many others. The CTX_ENTITY package implements entity extraction by means of a built-in dictionary and set of rules for English text. The capabilities can be extended for English, or for other languages, by means of user-provided add-on dictionaries and rule sets.

See Also:

See the topic "CTX_ENTITY Package" in Oracle Text Reference and the topic "Entity Extraction User Dictionary Loader (ctxload)" in Oracle Text Reference for additional information about using entity extraction

This section contains the following examples:

- Basic Example of Using Entity Extraction

- Example of Creating a New Entity Type Using a User-defined Rule

Basic Example of Using Entity Extraction

The example in this section provides a very simple, basic example of entity extraction. The example assumes that you have a clob containing the following text:

New York, United States of America
The Dow Jones Industrial Average climbed by 5% yesterday on news of a new software release from database giant Oracle Corporation.

The example uses CTX_ENTITY.EXTRACT to find all the entities in the CLOB value. (For now, do not worry about how the text got into the clob or how we provide the output clob)

Entity extraction requires a new type of policy, an "extract policy," which enables you to specify options. For now, we will create a default policy as follows:

ctx_entity.create_extract_policy( 'mypolicy' );

We can then call extract to do the work. It needs four arguments: the policy name, the document to process, the language, and the output clob (which must have been initialized, for example, by calling dbms_lob.createtemporary).

ctx_entity.extract( 'mypolicy', mydoc, 'ENGLISH', outclob )

outclob contains the XML identifying extracted entities. If we display the contents (preferably by selecting it as an XMLTYPE so it gets formatted nicely) we will see the following:

<entities>
<entity id="0" offset="0" length="8" source="SuppliedDictionary">
<text>New York</text>
<type>city</type>
</entity>
<entity id="1" offset="150" length="18" source="SuppliedRule">
<text>Oracle Corporation</text>
<type>company</type>
</entity>
<entity id="2" offset="10" length="24" source="SuppliedDictionary">
<text>United States of America</text>
<type>country</type>
</entity>
<entity id="3" offset="83" length="2" source="SuppliedRule">
<text>5%</text>
<type>percent</type>
</entity>
<entity id="4" offset="113" length="8" source="SuppliedDictionary">
<text>software</text>
<type>product</type>
</entity>
<entity id="5" offset="0" length="8" source="SuppliedDictionary">
<text>New York</text>
<type>state</type>
</entity>
</entities>

This is fine if we are going to process it with an XML-aware program. However, if we want it in a more "SQL friendly" view, we can use Oracle XML DB functions to convert it as follows:

select xtab.offset, xtab.text, xtab.type, xtab.source
from xmltable( '/entities/entity'
PASSING xmltype(outclob)
COLUMNS
offset number       PATH '@offset',
lngth number        PATH '@length',
text   varchar2(50) PATH 'text/text()',
type   varchar2(50) PATH 'type/text()',
source varchar2(50) PATH '@source'
) as xtab order by offset;

This produces the following output:

OFFSET TEXT                      TYPE                 SOURCE
---------- ------------------------- -------------------- --------------------
0 New York                  city                 SuppliedDictionary
0 New York                  state                SuppliedDictionary
10 United States of America  country              SuppliedDictionary
83 5%                        percent              SuppliedRule
113 software                  product              SuppliedDictionary
150 Oracle Corporation        company              SuppliedRule

If we do not want every different type of entity, we can select which types to fetch. We do this by adding a fourth argument to the "extract" procedure, with a comma-separated list of entity types. For example:

ctx_entity.extract( 'mypolicy', mydoc, 'ENGLISH', outclob, 'city, country' )

That would give us the XML

<entities>
<entity id="0" offset="0" length="8" source="SuppliedDictionary">
<text>New York</text>
<type>city</type>
</entity>
<entity id="2" offset="10" length="24" source="SuppliedDictionary">
<text>United States of America</text>
<type>country</type>
</entity>
</entities>

Example of Creating a New Entity Type Using a User-defined Rule

The example in this section shows how to create a new entity type using a user-defined rule. Rules are defined using a regular-expression-based syntax. The rule is added to an extraction policy, and will then be applied whenever that policy is used.

The rule will identify increases, for example, in a stock index. There are many ways to express an increase. We want our rule to match any of the following expressions:

climbed by 5%
increased by over 30 percent
jumped 5.5%

Therefore, we will create a regular expression that matches any of these, and create a new type of entity. User-defined entities must start with the letter "x", so we will call our entity "xPositiveGain" as follows:

ctx_entity.add_extract_rule( 'mypolicy', 1,
'<rule>'                                                          ||
'<expression>'                                                  ||
'((climbed|gained|jumped|increasing|increased|rallied)'      ||
'( (by|over|nearly|more than))* \d+(\.\d+)?( percent|%))'    ||
'</expression>'                                                 ||
'<type refid="1">xPositiveGain</type>'                          ||
'</rule>');

Note the use of refid in the example. This tells us which part of the regular expression to actually match, by referencing a pair of parentheses within it. In our case, we want the entire expression, so that is the outermost (and first occurring) parentheses, which is refid=1.

In this case, it is necessary to compile the policy with CTX_ENTITY.COMPILE:

ctx_entity.compile('mypolicy');

Then we can use it as before:

ctx_entity.extract('mypolicy', mydoc, null, myresults)

The (abbreviated) output of this is:

<entities>
...
<entity id="6" offset="72" length="18" source="UserRule" ruleid="1">
<text>climbed by over 5%</text>
<type>xPositiveGain</type>
</entity>
</entities>

Finally, we are going to add another user-defined entity, but this time it is using a dictionary. We want to recognize "Dow Jones Industrial Average" as an entity of type xIndex. We will add "S&P 500" as well. To do that, we create an XML file containing the following:

<dictionary>
<entities>
<entity>
<value>dow jones industrial average</value>
<type>xIndex</type>
</entity>
<entity>
<value>S&amp;P 500</value>
<type>xIndex</type>
</entity>
</entities>
</dictionary>

Case is not significant in this file, but note how the "&" in "S&P" must be specified as the XML entity &amp;. Otherwise, the XML would not be valid.

This XML file is loaded into the system using the CTXLOAD utility. If the file were called dict.load, we would use the following command:

ctxload -user username/password -extract -name mypolicy -file dict.load

You must compile the policy using CTX_ENTITY.COMPILE.

Fuzzy Matching and Stemming

Fuzzy matching enables you to match similarly spelled words in queries. Oracle Text provides entity extraction for multiple languages.

Stemming enables you to match words with the same linguistic root. For example a query on $speak, expands to search for all documents that contain speak, speaks, spoke, and spoken.

Fuzzy matching and stemming are automatically enabled in your index if Oracle Text supports this feature for your language.

Fuzzy matching is enabled with default parameters for its similarity score lower limit and for its maximum number of expanded terms. At index time you can change these default parameters.

To automatically detect the language of a document and to have the necessary transformations performed, create a stem index by enabling the index_stems attribute of the AUTO_LEXER. The stemmer that corresponds to the document language will be used and the stemmer will always be configured to maximize document recall. Additionally, for documents in languages that use compound words such as German, Finnish, Swedish, and Dutch, if index_stems is set to YES, then compound word stemming will automatically be performed. Compounds are always separated into their components stems.

To improve the performance of stem queries, create a stem index by enabling the index_stems attribute of the BASIC_LEXER.

- Values For Language Attribute for index_stems of AUTO_LEXER

- Values For Language Attribute for index_stems of BASIC_LEXER

See Also:

Oracle Text Reference to learn more about fuzzy matching and stemming

Values For Language Attribute for index_stems of BASIC_LEXER

The following values can be used with the index_stems attribute of BASIC_LEXER:

Value

Value cont'd

ARABIC

NYNORSK

BOKMAL

PERSIAN

CROATION

SERBIAN

DANISH

SLOVAK

FINNISH

SLOVENIAN

HEBREW

THAI

CATALAN

HUNGARIAN

CZECH

ITALIAN

DERIVATIONAL

ITALIAN_NEW

DERIVATIONAL_NEW

NONE

DUTCH

POLISH

DUTCH_NEW

PORTUGUESE

ENGLISH

ROMANIAN

ENGLISH_NEW

RUSSIAN

FRENCH

SPANISH

FRENCH_NEW

SPANISH_NEW

GERMAN

SWEDISH

GERMAN_NEW

TURKISH

GREEK

Values For Language Attribute for index_stems of AUTO_LEXER

The values for the index_stems attribute of AUTO_LEXER is TRUE or FALSE. The index_stems attribute of AUTO_LEXER supports the following languages:

Language

Language cont'd

ARABIC

NYNORSK

BOKMAL

PERSIAN

CROATION

SERBIAN

DANISH

SLOVAK

FINNISH

SLOVENIAN

HEBREW

THAI

CATALAN

KOREAN

CZECH

POLISH

DUTCH

PORTUGUESE

ENGLISH

ROMANIAN

FRENCH

RUSSIAN

GERMAN

SIMPLIFIED CHINEESE

GREEK

SPANISH

HUNGARIAN

SWEDISH

ITALIAN

TRADITIONAL CHINEESE

JAPANESE

TURKISH

Better Wildcard Query Performance

Wildcard queries enable you to enter left-truncated, right-truncated and doubly-truncated queries, such as %ing, cos%, or %benz%. With normal indexing, these queries can sometimes expand into large word lists, degrading your query performance.

Wildcard queries have better response time when token prefixes and substrings are recorded in the index.

By default, token prefixes and substrings are not recorded in the Oracle Text index. If your query application makes heavy use of wildcard queries, consider indexing token prefixes and substrings. To do so, use the wordlist preference type. The trade-off is a bigger index for improved wildcard searching.

See Also:

"BASIC_WORDLIST Example: Enabling Substring and Prefix Indexing"

Document Section Searching

For documents that have internal structure such as HTML and XML, you can define and index document sections. Indexing document sections enables you to narrow the scope of your queries to within pre-defined sections. For example, you can specify a query to find all documents that contain the term dog within a section you define as Headings.

Sections must be defined prior to indexing and specified with the section group preference.

Oracle Text provides section groups with system-defined section definitions for HTML and XML. You can also specify that the system automatically create sections from XML documents during indexing.

See Also:

Searching Document Sections in Oracle Text

Stopwords and Stopthemes

A stopword is a word that is not to be indexed. Usually stopwords are low information words in a given language such as this and that in English.

By default, Oracle Text provides a list of stopwords called a stoplist for indexing a given language. You can modify this list or create your own with the CTX_DDL package. You specify the stoplist in the parameter string of CREATE INDEX.

A stoptheme is a word that is prevented from being theme-indexed or prevented from contributing to a theme. You can add stopthemes with the CTX_DDL package.

You can search document themes with the ABOUT operator. You can retrieve document themes programatically with the CTX_DOC PL/SQL package.

- Language Detection and Stoplists

- Multi-Language Stoplists

Language Detection and Stoplists

At query time, the language of the query is inherited from the query template, or from the session language (if no language is specified through the query template).

Multi-Language Stoplists

You can also create multi-language stoplists to hold language-specific stopwords. A multi-language stoplist is useful when you use the MULTI_LEXER to index a table that contains documents in different languages, such as English, German, and Japanese.

At index creation, the language column of each document is examined, and only the stopwords for that language are eliminated. At query time, the session language setting determines the active stopwords, like it determines the active lexer when using the multi-lexer.

Index Performance

There are factors that influence indexing performance including memory allocation, document format, degree of parallelism, and partitioned tables.

See Also:

"Frequently Asked Questions About Indexing Performance"

Query Performance and Storage of Large Object (LOB) Columns

If your table contains Large Object (LOB) datatypes structured columns that are frequently accessed in queries but rarely updated, you can improve query performance by storing these columns out-of-line.

Note:

You cannot map attributes to a remote LOB column.

See Also:

"Does out-of-line LOB storage of wide base table columns improve performance?"

Mixed Query Performance

If your CONTAINS() query also has structured predicates on the non-text columns, then you may consider having the Text index also index those column values. To do so, specify those columns in the FILTER BY clause of the CREATE INDEX statement. This enables Oracle Text to determine whether to have the structured predicate(s) also be processed by the Text index for better performance.

Additionally, if your CONTAINS() query has ORDER BY criteria on one or more structured columns, then the Text index can also index those column values. Specify those columns in the ORDER BY clause of the CREATE INDEX statement. This enables Oracle Text to determine whether to push the sort into the Text index for better query response time.

See Also:

"CONTEXT Index Example: Query Processing with FILTER BY and ORDER BY"

Creating Oracle Text Indexes

With Oracle Text you can create indexes of type CONTEXT, CTXCAT, and CTXRULE.

This section contains these topics:

- Summary of Procedure for Creating a Text Index

- Creating Preferences

- Creating Section Groups for Section Searching

- Using Stopwords and Stoplists

- Creating a CONTEXT Index

- Creating a CTXCAT Index

- Creating a CTXRULE Index

Summary of Procedure for Creating a Text Index

By default, the system expects your documents to be stored in a text column. Once this requirement is satisfied, you can create a Text index using the CREATE INDEX SQL statement as an extensible index of type CONTEXT, without explicitly specifying any preferences. The system automatically detects your language, the datatype of the text column, format of documents, and sets indexing preferences accordingly.

See Also:

"Default CONTEXT Index Example"

To create an Oracle Text index:

1. Optionally, determine your custom indexing preferences, section groups, or stoplists if not using defaults. The following table describes these indexing classes:

Class

Description

Datastore

How are your documents stored?

Filter

How can the documents be converted to plaintext?

Lexer

What language is being indexed?

Wordlist

How should stem and fuzzy queries be expanded?

Storage

How should the index data be stored?

Stop List

What words or themes are not to be indexed?

Section Group

How are documents sections defined?

2. Optionally, create your own custom preferences, section groups, or stoplists. See "Creating Preferences ".

3. Create the Text index with the SQL statement CREATE INDEX, naming your index and optionally specifying preferences. See "Creating a CONTEXT Index".

See Also:

"Considerations for Oracle Text Indexing" and CREATE INDEX topic in Oracle Text Reference

Creating Preferences

You can optionally create your own custom index preferences to override the defaults. Use the preferences to specify index information such as where your files are stored and how to filter your documents. You create the preferences then set the attributes.

- Datastore Examples

- NULL_FILTER Example: Indexing HTML Documents

- PROCEDURE_FILTER Example

- BASIC_LEXER Example: Setting Printjoin Characters

- MULTI_LEXER Example: Indexing a Multi-Language Table

- BASIC_WORDLIST Example: Enabling Substring and Prefix Indexing

Datastore Examples

The following sections give examples for setting direct, multi-column, URL, and file datastores.

- Specifying DIRECT_DATASTORE

- Specifying MULTI_COLUMN_DATASTORE

- Specifying URL Data Storage

- Specifying File Data Storage

See Also:

Oracle Text Reference for more information about data storage

Specifying DIRECT_DATASTORE

The following example creates a table with a CLOB column to store text data. It then populates two rows with text data and indexes the table using the system-defined preference CTXSYS.DEFAULT_DATASTORE which uses the DIRECT_DATASTORE preference type.

create table mytable(id number primary key, docs clob);

insert into mytable values(111555,'this text will be indexed');
insert into mytable values(111556,'this is a default datastore example');
commit;

create index myindex on mytable(docs)
indextype is ctxsys.context
parameters ('DATASTORE CTXSYS.DEFAULT_DATASTORE');

Specifying MULTI_COLUMN_DATASTORE

The following example creates a multi-column datastore preference called my_multi on the three text columns to be concatenated and indexed:

begin
ctx_ddl.create_preference('my_multi', 'MULTI_COLUMN_DATASTORE');
ctx_ddl.set_attribute('my_multi', 'columns', 'column1, column2, column3');
end;

Specifying URL Data Storage

This example creates a URL_DATASTORE preference called my_url to which the http_proxy, no_proxy, and timeout attributes are set. The timeout attribute is set to 300 seconds. The defaults are used for the attributes that are not set.

begin
ctx_ddl.create_preference('my_url','URL_DATASTORE');
ctx_ddl.set_attribute('my_url','HTTP_PROXY','www-proxy.us.example.com');
ctx_ddl.set_attribute('my_url','NO_PROXY','us.example.com');
ctx_ddl.set_attribute('my_url','Timeout','300');
end;

Specifying File Data Storage

The following example creates a data storage preference using the FILE_DATASTORE. This tells the system that the files to be indexed are stored in the operating system. The example uses CTX_DDL.SET_ATTRIBUTE to set the PATH attribute of to the directory /docs.

begin
ctx_ddl.create_preference('mypref', 'FILE_DATASTORE');
ctx_ddl.set_attribute('mypref', 'PATH', '/docs');
end;

NULL_FILTER Example: Indexing HTML Documents

If your document set is entirely in HTML, then Oracle recommends that you use the NULL_FILTER in your filter preference, which does no filtering.

For example, to index an HTML document set, you can specify the system-defined preferences for NULL_FILTER and HTML_SECTION_GROUP as follows:

create index myindex on docs(htmlfile) indextype is ctxsys.context
parameters('filter ctxsys.null_filter
section group ctxsys.html_section_group');

PROCEDURE_FILTER Example

Consider a filter procedure CTXSYS.NORMALIZE that you define with the following signature:

PROCEDURE NORMALIZE(id IN ROWID, charset IN VARCHAR2, input IN CLOB,
output IN OUT NOCOPY VARCHAR2);

To use this procedure as your filter, you set up your filter preference as follows:

begin
ctx_ddl.create_preference('myfilt', 'procedure_filter');
ctx_ddl.set_attribute('myfilt', 'procedure', 'normalize');
ctx_ddl.set_attribute('myfilt', 'input_type', 'clob');
ctx_ddl.set_attribute('myfilt', 'output_type', 'varchar2');
ctx_ddl.set_attribute('myfilt', 'rowid_parameter', 'TRUE');
ctx_ddl.set_attribute('myfilt', 'charset_parameter', 'TRUE');
end;

BASIC_LEXER Example: Setting Printjoin Characters

Printjoin characters are non-alphanumeric characters that are to be included in index tokens, so that words such as web-site are indexed as web-site.

The following example sets printjoin characters to be the hyphen and underscore with the BASIC_LEXER:

begin
ctx_ddl.create_preference('mylex', 'BASIC_LEXER');
ctx_ddl.set_attribute('mylex', 'printjoins', '_-');
end;

To create the index with printjoins characters set as previously shown, enter the following statement:

create index myindex on mytable ( docs )
indextype is ctxsys.context
parameters ( 'LEXER mylex' );

MULTI_LEXER Example: Indexing a Multi-Language Table

You use the MULTI_LEXER preference type to index a column containing documents in different languages. For example, you can use this preference type when your text column stores documents in English, German, and French.

The first step is to create the multi-language table with a primary key, a text column, and a language column as follows:

create table globaldoc (
doc_id number primary key,
lang varchar2(3),
text clob
);

Assume that the table holds mostly English documents, with some German and Japanese documents. To handle the three languages, you must create three sub-lexers, one for English, one for German, and one for Japanese:

ctx_ddl.create_preference('english_lexer','basic_lexer');
ctx_ddl.set_attribute('english_lexer','index_themes','yes');
ctx_ddl.set_attribute('english_lexer','theme_language','english');

ctx_ddl.create_preference('german_lexer','basic_lexer');
ctx_ddl.set_attribute('german_lexer','composite','german');
ctx_ddl.set_attribute('german_lexer','mixed_case','yes');
ctx_ddl.set_attribute('german_lexer','alternate_spelling','german');

ctx_ddl.create_preference('japanese_lexer','japanese_vgram_lexer');

Create the multi-lexer preference:

ctx_ddl.create_preference('global_lexer', 'multi_lexer');

Because the stored documents are mostly English, make the English lexer the default using CTX_DDL.ADD_SUB_LEXER:

ctx_ddl.add_sub_lexer('global_lexer','default','english_lexer');

Now add the German and Japanese lexers in their respective languages with CTX_DDL.ADD_SUB_LEXER procedure. Also assume that the language column is expressed in the standard ISO 639-2 language codes, so add those as alternate values.

ctx_ddl.add_sub_lexer('global_lexer','german','german_lexer','ger');
ctx_ddl.add_sub_lexer('global_lexer','japanese','japanese_lexer','jpn');

Now create the index globalx, specifying the multi-lexer preference and the language column in the parameter clause as follows:

create index globalx on globaldoc(text) indextype is ctxsys.context
parameters ('lexer global_lexer language column lang');

BASIC_WORDLIST Example: Enabling Substring and Prefix Indexing

The following example sets the wordlist preference for prefix and substring indexing. Having a prefix and sub-string component to your index improves performance for wildcard queries.

For prefix indexing, the example specifies that Oracle Text create token prefixes between three and four characters long:

begin
ctx_ddl.create_preference('mywordlist', 'BASIC_WORDLIST');
ctx_ddl.set_attribute('mywordlist','PREFIX_INDEX','TRUE');
ctx_ddl.set_attribute('mywordlist','PREFIX_MIN_LENGTH', '3');
ctx_ddl.set_attribute('mywordlist','PREFIX_MAX_LENGTH', '4');
ctx_ddl.set_attribute('mywordlist','SUBSTRING_INDEX', 'YES');
end;

Creating Section Groups for Section Searching

When documents have internal structure such as in HTML and XML, you can define document sections using embedded tags before you index. This enables you to query within the sections using the WITHIN operator. You define sections as part of a section group.

Example: Creating HTML Sections

The following code defines a section group called htmgroup of type HTML_SECTION_GROUP. It then creates a zone section in htmgroup called heading identified by the <H1> tag:

begin
ctx_ddl.create_section_group('htmgroup', 'HTML_SECTION_GROUP');
ctx_ddl.add_zone_section('htmgroup', 'heading', 'H1');
end;

See Also:

Searching Document Sections in Oracle Text

Using Stopwords and Stoplists

A stopword is a word that is not to be indexed. A stopword is usually a low information word such as this or that in English.

The system supplies a list of stopwords called a stoplist for every language. By default during indexing, the system uses the Oracle Text default stoplist for your language.

You can edit the default stoplist CTXSYS.DEFAULT_STOPLIST or create your own with the following PL/SQL procedures:

- CTX_DDL.CREATE_STOPLIST

- CTX_DDL.ADD_STOPWORD

- CTX_DDL.REMOVE_STOPWORD

You specify your custom stoplists in the parameter clause of CREATE INDEX.

You can also dynamically add stopwords after indexing with the ALTER INDEX statement.

- Multi-Language Stoplists

- Stopthemes and Stopclasses

- PL/SQL Procedures for Managing Stoplists

Multi-Language Stoplists

You can create multi-language stoplists to hold language-specific stopwords. A multi-language stoplist is useful when you use the MULTI_LEXER to index a table that contains documents in different languages, such as English, German, and Japanese.

To create a multi-language stoplist, use the CTX_DDL.CREATE_STOPLIST procedure and specify a stoplist type of MULTI_STOPLIST. You add language specific stopwords with CTX_DDL.ADD_STOPWORD.

Stopthemes and Stopclasses

In addition to defining your own stopwords, you can define stopthemes, which are themes that are not to be indexed. This feature is available for English and French only.

You can also specify that numbers are not to be indexed. A class of alphanumeric characters such a numbers that is not to be indexed is a stopclass.

You record your own stopwords, stopthemes, stopclasses by creating a single stoplist, to which you add the stopwords, stopthemes, and stopclasses. You specify the stoplist in the paramstring for CREATE INDEX.

PL/SQL Procedures for Managing Stoplists

You use the following procedures to manage stoplists, stopwords, stopthemes, and stopclasses:

- CTX_DDL.CREATE_STOPLIST

- CTX_DDL.ADD_STOPWORD

- CTX_DDL.ADD_STOPTHEME

- CTX_DDL.ADD_STOPCLASS

- CTX_DDL.REMOVE_STOPWORD

- CTX_DDL.REMOVE_STOPTHEME

- CTX_DDL.REMOVE_STOPCLASS

- CTX_DDL.DROP_STOPLIST

See Also:

Oracle Text Reference to learn more about using these statements

Creating a CONTEXT Index

The CONTEXT index type is well suited for indexing large coherent documents in formats such as Microsoft Word, HTML, or plain text. With a CONTEXT index, you can also customize your index in a variety of ways. The documents must be loaded in a text table.

This section contains these topics:

- CONTEXT Index and DML

- Default CONTEXT Index Example

- Incrementally Creating an Index with ALTER INDEX and CREATE INDEX

- Creating a CONTEXT Index Incrementally with POPULATE_PENDING

- Custom CONTEXT Index Example: Indexing HTML Documents

- CONTEXT Index Example: Query Processing with FILTER BY and ORDER BY

CONTEXT Index and DML

A CONTEXT index is not transactional. When a record is deleted, the index change is immediate. That is, your own session will no longer find the record from the moment you make the change, and other users will not find the record as soon as you commit. For inserts and updates, the new information will not be visible to text searches until an index synchronization has occurred. Therefore, when you perform inserts or updates on the base table, you must explicitly synchronize the index with CTX_DDL.SYNC_INDEX.

See Also:

"Synchronizing the Index"

Default CONTEXT Index Example

The following statement creates a default CONTEXT index called myindex on the text column in the docs table:

CREATE INDEX myindex ON docs(text) INDEXTYPE IS CTXSYS.CONTEXT;

When you use CREATE INDEX without explicitly specifying parameters, the system does the following actions by default for all languages:

- Assumes that the text to be indexed is stored directly in a text column. The text column can be of type CLOB, BLOB, BFILE, VARCHAR2, or CHAR.

- Detects the column type and uses filtering for the binary column types of BLOB and BFILE. Most document formats are supported for filtering. If your column is plain text, the system does not use filtering.

Note:

For document filtering to work correctly in your system, you must ensure that your environment is set up correctly to support the AUTO_FILTER filter.

To learn more about configuring your environment to use the AUTO_FILTER filter, see the Oracle Text Reference.

- Assumes the language of text to index is the language you specify in your database setup.

- Uses the default stoplist for the language you specify in your database setup. Stoplists identify the words that the system ignores during indexing.

- Enables fuzzy and stemming queries for your language, if this feature is available for your language.

You can always change the default indexing behavior by creating your own preferences and specifying these custom preferences in the parameter string of CREATE INDEX.

Incrementally Creating an Index with ALTER INDEX and CREATE INDEX

The ALTER INDEX and CREATE INDEX statements support incrementally creating a global CONTEXT index.

- For creating a global index, CREATE INDEX supports the NOPOPULATE keyword of the REBUILD clause. Using the NOPOPULATE keyword in the REPLACE parameter, you can create indexes incrementally. This is valuable for creating text indexes in large installations that cannot afford to have the indexing process running continuously.

- For creating a local index partition, ALTER INDEX ... REBUILD partition ... parameters ('REPLACE ...') parameter string is modified to support the NOPOPULATE keyword.

- For creating a partition on a local index, CREATE INDEX ... LOCAL ... (partition ... parameters ('NOPOPULATE')) is supported. The partition-level POPULATE or NOPOPULATE keywords override any POPULATE or NOPOPULATE specified at the index level.

See Also:

Oracle Text Reference to learn more about the syntax for the ALTER INDEX and CREATE INDEX statements

Creating a CONTEXT Index Incrementally with POPULATE_PENDING

For large installations that cannot afford to have the indexing process run continuously, you can use the CTX_DDL.POPULATE_PENDING procedure. This also provides finer control over creating the indexes. The preferred method is to create an empty index, place all the rowids into the pending queue, and build the index through CTX_DDL.SYNC_INDEX.

This procedure populates the pending queue with every rowid in the base table or table partition.

See Also:

Oracle Text Reference for information about CTX_DDL.POPULATE_PENDING

Custom CONTEXT Index Example: Indexing HTML Documents

To index an HTML document set located by URLs, you can specify the system-defined preference for the NULL_FILTER in the CREATE INDEX statement.

You can also specify your section group htmgroup that uses HTML_SECTION_GROUP and datastore my_url that uses URL_DATASTORE as follows:

begin
ctx_ddl.create_preference('my_url','URL_DATASTORE');
ctx_ddl.set_attribute('my_url','HTTP_PROXY','www-proxy.us.example.com');
ctx_ddl.set_attribute('my_url','NO_PROXY','us.example.com');
ctx_ddl.set_attribute('my_url','Timeout','300');
end;

begin
ctx_ddl.create_section_group('htmgroup', 'HTML_SECTION_GROUP');
ctx_ddl.add_zone_section('htmgroup', 'heading', 'H1');
end;

You can then index your documents as follows:

CREATE INDEX myindex on docs(htmlfile) indextype is ctxsys.context
parameters(
'datastore my_url filter ctxsys.null_filter section group htmgroup'
);

See Also:

"Creating Preferences " for more examples on creating a custom context index

CONTEXT Index Example: Query Processing with FILTER BY and ORDER BY

To enable more efficient query processing and better response time for mixed queries, you can use FILTER BY and ORDER BY clauses as shown in the following example.

CREATE INDEX myindex on docs(text) INDEXTYPE is CTXSYS.CONTEXT
FILTER BY category, publisher, pub_date
ORDER BY pub_date desc;

In this example, by specifying the clause FILTER BY category, publisher, pub_date at query time, Oracle Text will also consider pushing any relational predicate on any of these columns into the Text index row source for more efficient query processing.

Also, when the query has matching ORDER BY criteria, by specifying ORDER BY pub_date desc, Oracle Text will determine whether to push the SORT into the Text index row source for better response time.

DATASTORE Triggers in Release 12c

If you want to create an Oracle Text CONTEXT index on multiple columns, you would normally use a MULTI_COLUMN_DATASTORE or USER_DATASTORE to bring in the various columns for indexing. Oracle Text will update the index only when the contents of a particular column that you specify has changed.

Creating a CTXCAT Index

The CTXCAT index type is well-suited for indexing small text fragments and related information. If created correctly, this type of index can provide better structured query performance over a CONTEXT index.

- CTXCAT Index and DML

- About CTXCAT Sub-Indexes and Their Costs

- Creating CTXCAT Sub-indexes

- Creating CTXCAT Index

CTXCAT Index and DML

A CTXCAT index is transactional. When you perform DML (inserts, updates, and deletes) on the base table, Oracle Text automatically synchronizes the index. Unlike a CONTEXT index, no CTX_DDL.SYNC_INDEX is necessary.

Note:

Applications that insert without invoking triggers such as SQL*Loader will not result in automatic index synchronization as described in this section.

About CTXCAT Sub-Indexes and Their Costs

A CTXCAT index comprises sub-indexes that you define as part of your index set. You create a sub-index on one or more columns to improve mixed query performance. However, adding sub-indexes to the index set has its costs. The time Oracle Text takes to create a CTXCAT index depends on its total size, and the total size of a CTXCAT index is directly related to the following factors:

- Total text to be indexed

- Number of sub-indexes in the index set

- Number of columns in the base table that make up the sub-indexes

Having many component indexes in your index set also degrades DML performance, because more indexes must be updated.

Because of the added index time and disk space costs for creating a CTXCAT index, carefully consider the query performance benefit that each component index gives your application before adding it to your index set.

Note:

You can use I_ROWID_INDEX_CLAUSE of BASIC_STORAGE to speed up the creation of a CTXCAT index. This clause is described in Oracle Text Reference.

Creating CTXCAT Sub-indexes

An online auction site that must store item descriptions, prices and bid-close dates for ordered look-up provides a good example for creating a CTXCAT index.

Figure 3-3 Auction Table Schema and CTXCAT Index

Figure 3-3 shows a table called AUCTION with the following schema:

create table auction(
item_id number,
title varchar2(100),
category_id number,
price number,
bid_close date);

To create your sub-indexes, create an index set to contain them:

begin
ctx_ddl.create_index_set('auction_iset');
end;

Next, determine the structured queries your application is likely to enter. The CATSEARCH query operator takes a mandatory text clause and optional structured clause.

In our example, this means all queries include a clause for the title column which is the text column.

Assume that the structured clauses fall into the following categories:

Structured Clauses

Sub-index Definition to Serve Query

Category

'price < 200'

'price = 150'

'order by price'

'price'

A

'price = 100 order by bid_close'

'order by price, bid_close'

'price, bid_close'

B

Structured Query Clause Category A

The structured query clause contains an expression for only the price column as follows:

SELECT FROM auction WHERE CATSEARCH(title, 'camera', 'price < 200')> 0;
SELECT FROM auction WHERE CATSEARCH(title, 'camera', 'price = 150')> 0;
SELECT FROM auction WHERE CATSEARCH(title, 'camera', 'order by price')> 0;

These queries can be served using sub-index B, but for efficiency you can also create a sub-index only on price, which we call sub-index A:

begin
ctx_ddl.add_index('auction_iset','price'); /* sub-index A */
end;

Structured Query Clause Category B

The structured query clause includes an equivalence expression for price ordered by bid_close, and an expression for ordering by price and bid_close in that order:

SELECT FROM auction WHERE CATSEARCH(
title, 'camera','price = 100
ORDER BY bid_close')> 0;
SELECT FROM auction
WHERE CATSEARCH(
title, 'camera','order by price, bid_close')> 0;

These queries can be served with a sub-index defined as follows:

begin
ctx_ddl.add_index('auction_iset','price, bid_close'); /* sub-index B */
end;

Like a combined b-tree index, the column order you specify with CTX_DDL.ADD_INDEX affects the efficiency and viability of the index scan Oracle Text uses to serve specific queries. For example, if two structured columns p and q have a b-tree index specified as 'p,q', Oracle Text cannot scan this index to sort 'ORDER BY q,p'.

Creating CTXCAT Index

The following example combines the previous examples and creates the index set preference with the two sub-indexes:

begin
ctx_ddl.create_index_set('auction_iset');
ctx_ddl.add_index('auction_iset','price'); /* sub-index A */
ctx_ddl.add_index('auction_iset','price, bid_close'); /* sub-index B */
end;

Figure 3-3 shows how the sub-indexes A and B are created from the auction table. Each sub-index is a b-tree index on the text column and the named structured columns. For example, sub-index A is an index on the title column and the bid_close column.

You create the combined catalog index with CREATE INDEX as follows:

CREATE INDEX auction_titlex ON AUCTION(title)
INDEXTYPE IS CTXSYS.CTXCAT
PARAMETERS ('index set auction_iset')
;

See Also:

Oracle Text Reference to learn more about creating a CTXCAT index with CREATEINDEX

Creating a CTXRULE Index

You use the CTXRULE index to build a document classification application. In such an application, a stream of incoming documents is classified based on their content. Document routing is achieved by creating a CTXRULE index on a table or queries. The queries define your categories. You can use the MATCHES operator to classify single documents.

This section contains the following steps toward creating a CTXRULE index and a simple document classification application:

- Step One: Create a Table of Queries

- Step Two: Create the CTXRULE Index

- Step Three: Classify a Document

See Also:

Classifying Documents in Oracle Text for more information on document classification and the CTXRULE index

Step One: Create a Table of Queries

The first step is to create a table of queries that define your classifications. We create a table myqueries to hold the category name and query text:

CREATE TABLE myqueries (
queryid NUMBER PRIMARY KEY,
category VARCHAR2(30),
query VARCHAR2(2000)
);

Populate the table with the classifications and the queries that define each. For example, consider a classification for the subjects US Politics, Music, and Soccer.:

INSERT INTO myqueries VALUES(1, 'US Politics', 'democrat or republican');
INSERT INTO myqueries VALUES(2, 'Music', 'ABOUT(music)');
INSERT INTO myqueries VALUES(3, 'Soccer', 'ABOUT(soccer)');

Using CTX_CLS.TRAIN

You can also generate a table of rules (or queries) with the CTX_CLS.TRAIN procedure, which takes as input a document training set.

See Also:

Oracle Text Reference for more information on CTX_CLS.TRAIN

Step Two: Create the CTXRULE Index

Use CREATE INDEX to create the CTXRULE index. You can specify lexer, storage, section group, and wordlist parameters if needed:

CREATE INDEX myruleindex ON myqueries(query)
INDEXTYPE IS CTXRULE PARAMETERS
('lexer lexer_pref
storage storage_pref
section group section_pref
wordlist wordlist_pref');

Step Three: Classify a Document

With a CTXRULE index created on a query set, you can use the MATCHES operator to classify a document.

Assume that incoming documents are stored in the table news:

CREATE TABLE news (
newsid NUMBER,
author VARCHAR2(30),
source VARCHAR2(30),
article CLOB);

You can create a "before insert" trigger with MATCHES to route each document to another table news_route based on its classification:

BEGIN
-- find matching queries
FOR c1 IN (select category
from myqueries
where MATCHES(query, :new.article)>0)
LOOP
INSERT INTO news_route(newsid, category)
VALUES (:new.newsid, c1.category);
END LOOP;
END;

Maintaining Oracle Text Indexes

This section describes maintaining your index in the event of an error or indexing failure. The following topics are included:

- Viewing Index Errors

- Dropping an Index

- Resuming Failed Index

- Re-creating an Index

- Rebuilding an Index

- Dropping a Preference

Viewing Index Errors

Sometimes an indexing operation might fail or not complete successfully. When the system encounters an error during indexing a row, it logs the error in an Oracle Text view.

You can view errors on your indexes with CTX_USER_INDEX_ERRORS. View errors on all indexes as CTXSYS with CTX_INDEX_ERRORS.

For example, to view the most recent errors on your indexes, enter the following statement:

SELECT err_timestamp, err_text
FROM ctx_user_index_errors
ORDER BY err_timestamp DESC;

To clear the view of errors, enter:

DELETE FROM ctx_user_index_errors;

This view is cleared automatically when you create a new index.

See Also:

Oracle Text Reference to learn more about the index error views

Dropping an Index

You must drop an existing index before you can re-create it with CREATE INDEX.

Drop an index using the DROP INDEX statement in SQL.

If you try to create an index with an invalid PARAMETERS string, then you still need to drop it before you can re-create it.

For example, to drop an index called newsindex, enter the following SQL statement:

DROP INDEX newsindex;

If Oracle Text cannot determine the state of the index, for example as a result of an indexing malfunction, you cannot drop the index as described previously. Instead use:

DROP INDEX newsindex FORCE;

See Also:

Oracle Text Reference to learn more about the DROP INDEX statement

Resuming Failed Index

You can sometimes resume a failed index creation operation using the ALTER INDEX statement. You typically resume a failed index after you have investigated and corrected the index failure. Not all index failures can be resumed.

Index optimization commits at regular intervals. Therefore, if an optimization operation fails, then all optimization work up to the commit point has already been saved.

See Also:

Oracle Text Reference to learn more about the ALTER INDEX statement syntax

The following statement resumes the indexing operation on newsindex with 10 megabytes of memory:

ALTER INDEX newsindex REBUILD PARAMETERS('resume memory 10M');

Re-creating an Index

This section describes the procedures available for re-creating an index, which enable index settings to be changed. During the re-creation process, the index can be queried normally.

- Re-creating a Global Index

- Re-creating a Local Partitioned Index

- Re-creating a Global Index with Time Limit for Synch

- Re-creating a Global Index with Scheduled Swap

- Re-creating a Local Index with All-at-Once Swap

- Scheduling Local Index Re-creation with All-at-Once Swap

- Re-creating a Local Index with Per-Partition Swap

Re-creating a Global Index

Oracle Text provides RECREATE_INDEX_ONLINE to re-create a CONTEXT index with new preferences, while preserving the base table DML and query capability during the re-create process. You can use RECREATE_INDEX_ONLINE in a one step procedure to re-create a CONTEXT index online for global indexes. Because the new index is created alongside the existing index, this operation requires storage roughly equal to the size of the existing index. Also, because the RECREATE_INDEX_ONLINE operation is performed online, you may issue DML on the base table during the operation. All DML that occurs during re-creation is logged into an online pending queue.

- After the re-create index operation is complete, any new information resulting from DML during the re-creation process may not be immediately reflected. As with creating an index online, the index should be synchronized after the re-create index operation is complete in order to bring it fully up-to-date.

- Synchronizations issued against the index during the re-creation are processed against the old, existing data. Synchronizations are blocked during this time when queries return errors.

- Optimize commands issued against the index during the re-creation return immediately without error and without processing.

- During RECREATE_INDEX_ONLINE, the index can be queried normally most of the time. Queries return results based on the existing index and policy until after the final swap. Also, if you issue DML statements and synchronize them, then you will be able to see the new rows when you query on the existing index.

See Also:

Oracle Text Reference to learn more about the RECREATE_INDEX_ONLINE procedure

Note:

Transactional query is not supported with RECREATE_INDEX_ONLINE.

Re-creating a Local Partitioned Index

If the index is locally partitioned, you cannot re-create the index in one step. You must first create a shadow policy, and then run the RECREATE_INDEX_ONLINE procedure for every partition. You can specify SWAP or NOSWAP, which indicates whether re-creating the index for the partition will swap the index partition data and index partition metadata.

This procedure can also be used to update the metadata (for example the storage preference) of each partition when you specify NOPOPULATE in the parameter string. This is useful for incremental building of a shadow index through time-limited synchronization. If NOPOPULATE is specified, then NOSWAP is silently enforced.

- When all of the partitions use NOSWAP, the storage requirement is approximately equal to the size of the existing index. During the re-creation of the index partition, since no swapping is performed, queries on the partition are processed normally. Queries spanning multiple partitions return consistent results across partitions until the swapping stage is reached.

- When the partitions are rebuilt with SWAP, the storage requirement for the operation is equal to the size of the existing index partition. Since index partition data and metadata are swapped after re-creation, queries spanning multiple partitions will not return consistent results from partition to partition, but will always be correct with respect to each index partition.

- If SWAP is specified, then DML and synchronization on the partition are blocked during the swap process.

See Also:

Oracle Text Reference for complete information about RECREATE_INDEX_ONLINE

Re-creating a Global Index with Time Limit for Synch

You can control index re-creation to set a time limit for SYNC_INDEX during non-business hours and incrementally re-create the index. You use the CREATE_SHADOW_INDEX procedure with POPULATE_PENDING and maxtime.

See Also:

Oracle Text Reference for information and examples for CREATE_SHADOW_INDEX

Re-creating a Global Index with Scheduled Swap

With CTX_DDL.EXCHANGE_SHADOW_INDEX you can perform index re-creation during non-business hours when query failures and DML blocking can be tolerated.

See Also:

Oracle Text Reference for information and examples for CTX_DDL.EXCHANGE_SHADOW_INDEX

Re-creating a Local Index with All-at-Once Swap

You can re-create a local partitioned index online to create or change preferences. The swapping of the index and partition metadata occurs at the end of the process. Queries spanning multiple partitions return consistent results across partitions when re-create is in process, except at the end when EXCHANGE_SHADOW_INDEX is running.

Scheduling Local Index Re-creation with All-at-Once Swap

With RECREATE_INDEX_ONLINE of the CTX.DDL package, you can incrementally re-create a local partitioned index, where partitions are all swapped at the end.

See Also:

Oracle Text Reference for complete information and the example for this process with RECREATE_INDEX_ONLINE

Re-creating a Local Index with Per-Partition Swap

Instead of swapping all partitions at once, you can re-create the index online with new preferences, with each partition being swapped as it is completed. Queries across all partitions may return inconsistent results during this process. This procedure uses CREATE_SHADOW_INDEX with RECREATE_INDEX_ONLINE.

See Also:

Oracle Text Reference for an example of swapping index partitions with the RECREATE_INDEX_ONLINE procedure

Rebuilding an Index

You can rebuild a valid index using ALTER INDEX. Rebuilding an index does not allow most index settings to be changed. You might rebuild an index when you want to index with a new preference. Generally, there is no advantage in rebuilding an index over dropping it and re-creating it with CREATE INDEX.

See Also:

"Re-creating an Index" for information about changing index settings

Example: Rebuilding an Index

The following statement rebuilds the index, replacing the lexer preference with my_lexer.

ALTER INDEX newsindex REBUILD PARAMETERS('replace lexer my_lexer');

Dropping a Preference

You might drop a custom index preference when you no longer need it for indexing.

You drop index preferences with the procedure CTX_DDL.DROP_PREFERENCE.

Dropping a preference does not affect the index created from the preference.

See Also:

Oracle Text Reference to learn more about the syntax for the CTX_DDL.DROP_PREFERENCE procedure

Example: Dropping a Preference

The following code drops the preference my_lexer.

begin
ctx_ddl.drop_preference('my_lexer');
end;

Managing DML Operations for a CONTEXT Index

DML operations to the base table refer to when documents are inserted, updated, or deleted from the base table. This section describes how you can monitor, synchronize, and optimize the Oracle Text CONTEXT index when DML operations occur. This section contains the following topics:

- Viewing Pending DML

- Synchronizing the Index

- Optimizing the Index

Note:

CTXCAT indexes are transactional and, thus, they are updated immediately when there is a change to the base table. Manual synchronization as described in this section is not necessary for a CTXCAT index.

Viewing Pending DML

When documents in the base table are inserted or updated, their ROWIDs are held in a DML queue until you synchronize the index. You can view this queue with the CTX_USER_PENDING view.

For example, to view pending DML on all your indexes, enter the following statement:

SELECT pnd_index_name, pnd_rowid, to_char(
pnd_timestamp, 'dd-mon-yyyy hh24:mi:ss'
) timestamp FROM ctx_user_pending;

This statement gives output in the form:

PND_INDEX_NAME                 PND_ROWID          TIMESTAMP
------------------------------ ------------------ --------------------
MYINDEX                        AAADXnAABAAAS3SAAC 06-oct-1999 15:56:50

See Also:

Oracle Text Reference to learn more about the CTX_USER_PENDING view

Synchronizing the Index

Synchronizing the index involves processing all pending updates and inserts to the base table. You can do this in PL/SQL with the CTX_DDL.SYNC_INDEX procedure. The following sections describe how you can control the duration and locking behavior for synchronizing an index:

- Synchronizing the Index With SYNC_INDEX

- Maxtime Parameter for SYNC_INDEX

- Locking Parameter for SYNC_INDEX

Synchronizing the Index With SYNC_INDEX

The following example synchronizes the index with 2 megabytes of memory:

begin

ctx_ddl.sync_index('myindex', '2M');

end;

See Also:

Oracle Text Reference to learn more about the CTX_DDL.SYNC_INDEX statement syntax

Maxtime Parameter for SYNC_INDEX

The sync_index procedure includes a maxtime parameter that, like optimize_index, indicates a suggested time limit in minutes for the operation. The sync_index will process as many documents in the queue as possible within the given time limit.

- NULL maxtime is equivalent to CTX_DDL.MAXTIME_UNLIMITED.

- The time limit is approximate. The actual time taken may be somewhat less than, or greater than what you specify.

- There is no change to the ALTER INDEX... sync command, which is deprecated.

- The maxtime parameter is ignored when sync_index is invoked without an index name.

- The maxtime parameter cannot be communicated for automatic synchronizations (for example, sync on commit or sync every).

Locking Parameter for SYNC_INDEX

The locking parameter of sync_index enables you to configure how the synchronization deals with the scenario where another sync is already running on the index.

- The locking parameter is ignored when sync_index is invoked without an index name.

- The locking parameter cannot be communicated for automatic syncs (i.e. sync on commit/sync every).

- When locking mode is LOCK_WAIT, in the event of not being able to get a lock, it will wait forever and ignore the maxtime setting.

The options are as follows:

Option

Description

CTX_DDL.LOCK_WAIT

If another sync is running, wait until the running sync is complete, then begin new sync.

CTX_DDL.LOCK_NOWAIT

If another sync is running, immediately return without error.

CTX_DDL.LOCK_NOWAIT_ERROR

If another sync is running, immediately raise an error (DRG-51313: timeout while waiting for DML or optimize lock).

Optimizing the Index

Frequent index synchronization ultimately causes fragmentation of your CONTEXT index. Index fragmentation can adversely affect query response time. You should, therefore, allow time to optimize your CONTEXT index in order to reduce fragmentation and index size and to ensure optimal query performance. To understand index optimization, you must understand the structure of the index and what happens when it is synchronized.

This section contains the following topics.

- CONTEXT Index Structure

- Index Fragmentation

- Document Invalidation and Garbage Collection

- Single Token Optimization

- Viewing Index Fragmentation and Garbage Data

- Example: Optimizing the Index

CONTEXT Index Structure

The CONTEXT index is an inverted index where each word contains the list of documents that contain that word. For example, after a single initial indexing operation, the word DOG might have an entry as follows:

DOG DOC1 DOC3 DOC5

Index Fragmentation

When new documents are added to the base table, the index is synchronized by adding new rows. Thus, if you add a new document (for example, DOC 7) with the word dog to the base table and synchronize the index, you now have:

DOG DOC1 DOC3 DOC5
DOG DOC7

Subsequent DML will also create new rows as follows:

DOG DOC1 DOC3 DOC5
DOG DOC7
DOG DOC9
DOG DOC11

Adding new documents and synchronizing the index causes index fragmentation. In particular, background DML, which synchronizes the index frequently, generally produces more fragmentation than synchronizing in batch mode.

Less frequent batch processing results in longer document lists, reducing the number of rows in the index and thus reducing fragmentation.

You can reduce index fragmentation by optimizing the index in either FULL or FAST mode with CTX_DDL.OPTIMIZE_INDEX.

Document Invalidation and Garbage Collection

When documents are removed from the base table, Oracle Text marks the document as removed but does not immediately alter the index.

Because the old information takes up space and can cause extra overhead at query time, you must remove the old information from the index by optimizing it in FULL mode. This is called garbage collection. Optimizing in FULL mode for garbage collection is necessary when you have frequent updates or deletes to the base table.

Single Token Optimization

In addition to optimizing the entire index, you can optimize single tokens. You can use token mode to optimize index tokens that are frequently searched, without spending time on optimizing tokens that are rarely referenced.

For example, you can specify that only the token DOG be optimized in the index, if you know that this token is updated and queried frequently.

An optimized token can improve query response time for the token.

To optimize an index in token mode, use CTX_DDL.OPTIMIZE_INDEX.

Viewing Index Fragmentation and Garbage Data

With the CTX_REPORT.INDEX_STATS procedure, you can create a statistical report on your index. The report includes information on optimal row fragmentation, a list of most fragmented tokens, and the amount of garbage data in your index. Although this report might take a long time to run for large indexes, it can help you decide whether to optimize your index.

See Also:

Oracle Text Reference to learn more about using the CTX_REPORT.INDEX_STATS procedure

Example: Optimizing the Index

To optimize an index, Oracle recommends that you use CTX_DDL.OPTIMIZE_INDEX.

See Also:

Oracle Text Reference for the CTX_DDL.OPTIMIZE_INDEX statement syntax and examples

4 Querying with Oracle Text

This chapter describes Oracle Text querying and associated features.

This chapter contains the following topics:

- Overview of Queries

- The CONTEXT Grammar

- The CTXCAT Grammar

Overview of Queries

The basic Oracle Text query takes a query expression, usually a word with or without operators, as input. Oracle Text returns all documents (previously indexed) that satisfy the expression along with a relevance score for each document. Scores can be used to order the documents in the result set.

To enter an Oracle Text query, use the SQL SELECT statement. Depending on the type of index you create, you use either the CONTAINS or CATSEARCH operator in the WHERE clause. You can use these operators programatically wherever you can use the SELECT statement, such as in PL/SQL cursors.

Use the MATCHES operator to classify documents with a CTXRULE index.

- Querying with CONTAINS

- Querying with CATSEARCH

- Querying with MATCHES

- Word and Phrase Queries

- Querying Stopwords

- ABOUT Queries and Themes

- Query Expressions

- Case-Sensitive Searching

- Query Feedback

- Query Explain Plan

- Using a Thesaurus in Queries

- About Document Section Searching

- Using Query Templates

- Query Rewrite

- Query Relaxation

- Query Language

- Ordering By SDATA Sections

- Alternative and User-defined Scoring

- Alternative Grammar

- Query Analysis

- Other Query Features

Querying with CONTAINS

When you create an index of type CONTEXT, you must use the CONTAINS operator to enter your query. An index of type CONTEXT is suited for indexing collections of large coherent documents.

With the CONTAINS operator, you can use a number of operators to define your search criteria. These operators enable you to enter logical, proximity, fuzzy, stemming, thesaurus and wildcard searches. With a correctly configured index, you can also enter section searches on documents that have internal structure such as HTML and XML.

With CONTAINS, you can also use the ABOUT operator to search on document themes.

- CONTAINS SQL Example

- CONTAINS PL/SQL Example

- Structured Query with CONTAINS

CONTAINS SQL Example

In the SELECT statement, specify the query in the WHERE clause with the CONTAINS operator. Also specify the SCORE operator to return the score of each hit in the hitlist. The following example shows how to enter a query:

SELECT SCORE(1), title from news WHERE CONTAINS(text, 'oracle', 1) > 0;

You can order the results from the highest scoring documents to the lowest scoring documents using the ORDER BY clause as follows:

SELECT SCORE(1), title from news
WHERE CONTAINS(text, 'oracle', 1) > 0
ORDER BY SCORE(1) DESC;

The CONTAINS operator must always be followed by the > 0 syntax, which specifies that the score value returned by the CONTAINS operator must be greater than zero for the row to be returned.

When the SCORE operator is called in the SELECT statement, the CONTAINS operator must reference the score label value in the third parameter as in the previous example.

CONTAINS PL/SQL Example

In a PL/SQL application, you can use a cursor to fetch the results of the query.

The following example enters a CONTAINS query against the NEWS table to find all articles that contain the word oracle. The titles and scores of the first ten hits are output.

declare
rowno number := 0;
begin
for c1 in (SELECT SCORE(1) score, title FROM news
WHERE CONTAINS(text, 'oracle', 1) > 0
ORDER BY SCORE(1) DESC)
loop
rowno := rowno + 1;
dbms_output.put_line(c1.title||': '||c1.score);
exit when rowno = 10;
end loop;
end;

This example uses a cursor FOR loop to retrieve the first ten hits. An alias score is declared for the return value of the SCORE operator. The score and title are output to standard out using cursor dot notation.

Structured Query with CONTAINS

A structured query, also called a mixed query, is a query that has a CONTAINS predicate to query a text column and has another predicate to query a structured data column.

To enter a structured query, you specify the structured clause in the WHERE condition of the SELECT statement.

For example, the following SELECT statement returns all articles that contain the word oracle that were written on or after October 1, 1997:

SELECT SCORE(1), title, issue_date from news
WHERE CONTAINS(text, 'oracle', 1) > 0
AND issue_date >= ('01-OCT-97')
ORDER BY SCORE(1) DESC;

Note:

Even though you can enter structured queries with CONTAINS, consider creating a CTXCAT index and issuing the query with CATSEARCH, which offers better structured query performance.

Querying with CATSEARCH

When you create an index of type CTXCAT, you must use the CATSEARCH operator to enter your query. An index of type CTXCAT is best suited when your application stores short text fragments in the text column and other associated information in related columns.

For example, an application serving an online auction site might have a table that stores item description in a text column and associated information such as date and price in other columns. With a CTXCAT index, you can create b-tree indexes on one or more of these columns. The result is that when you use the CATSEARCH operator to search a CTXCAT index, query performance is generally faster for mixed queries.

The operators available for CATSEARCH queries are limited to logical operations such as AND or OR. The operators you can use to define your structured criteria are greater than, less than, equality, BETWEEN, and IN.

- CATSEARCH SQL Query

- CATSEARCH Example

CATSEARCH SQL Query

A typical query with CATSEARCH might include a structured clause as follows to find all rows that contain the word camera ordered by the bid_close date:

SELECT FROM auction WHERE CATSEARCH(title, 'camera', 'order by bid_close desc')> 0;

The type of structured query you can enter depends on how you create your sub-indexes.

See Also:

"Creating a CTXCAT Index"

As shown in the previous example, you specify the structured part of a CATSEARCH query with the third structured_query parameter. The columns you name in the structured expression must have a corresponding sub-index.

For example, assuming that category_id and bid_close have a sub-index in the ctxcat index for the AUCTION table, enter the following structured query:

SELECT FROM auction WHERE CATSEARCH(title, 'camera', 'category_id=99 order by bid_close desc')> 0;

CATSEARCH Example

The following example shows a field section search against a CTXCAT index using CONTEXT grammar by means of a query template in a CATSEARCH query.

-- Create and populate table
create table BOOKS (ID number, INFO varchar2(200), PUBDATE DATE);

insert into BOOKS values(1, '<author>NOAM CHOMSKY</author><subject>CIVIL
RIGHTS</subject><language>ENGLISH</language><publisher>MIT
PRESS</publisher>', '01-NOV-2003');

insert into BOOKS values(2, '<author>NICANOR PARRA</author><subject>POEMS
AND ANTIPOEMS</subject><language>SPANISH</language>
<publisher>VASQUEZ</publisher>', '01-JAN-2001');

insert into BOOKS values(1, '<author>LUC SANTE</author><subject>XML
DATABASE</subject><language>FRENCH</language><publisher>FREE
PRESS</publisher>', '15-MAY-2002');

commit;

-- Create index set and section group
exec ctx_ddl.create_index_set('BOOK_INDEX_SET');
exec ctx_ddl.add_index('BOOK_INDEX_SET','PUBDATE');

exec ctx_ddl.create_section_group('BOOK_SECTION_GROUP',
'BASIC_SECTION_GROUP');
exec ctx_ddl.add_field_section('BOOK_SECTION_GROUP','AUTHOR','AUTHOR');
exec ctx_ddl.add_field_section('BOOK_SECTION_GROUP','SUBJECT','SUBJECT');
exec ctx_ddl.add_field_section('BOOK_SECTION_GROUP','LANGUAGE','LANGUAGE');
exec ctx_ddl.add_field_section('BOOK_SECTION_GROUP','PUBLISHER','PUBLISHER');

-- Create index
create index books_index on books(info) indextype is ctxsys.ctxcat
parameters('index set book_index_set section group book_section_group');

-- Use the index
-- Note that: even though CTXCAT index can be created with field sections, it
-- cannot be accessed using CTXCAT grammar (default for CATSEARCH).
-- We need to use query template with CONTEXT grammar to access field
-- sections with CATSEARCH

select  id, info from books
where catsearch(info,
'<query>
<textquery grammar="context">
NOAM within author and english within language
</textquery>
</query>',
'order by pubdate')>0;

Querying with MATCHES

When you create an index of type CTXRULE, you must use the MATCHES operator to classify your documents. The CTXRULE index is essentially an index on the set of queries that define your classifications.

For example, if you have an incoming stream of documents that need to be routed according to content, you can create a set of queries that define your categories. You create the queries as rows in a text column. It is possible to create this type of table with the CTX_CLS.TRAIN procedure.

You then index the table to create a CTXRULE index. When documents arrive, you use the MATCHES operator to classify each document

- MATCHES SQL Query

- MATCHES PL/SQL Example

See Also:

Classifying Documents in Oracle Text

MATCHES SQL Query

A MATCHES query finds all rows in a query table that match a given document. Assuming that a table querytable has a CTXRULE index associated with it, enter the following query:

SELECT classification FROM querytable WHERE MATCHES(query_string,:doc_text) > 0;

Note the bind variable :doc_text which contains the document CLOB to be classified.

Combining everything into a simple example:

create table queries (
query_id      number,
query_string  varchar2(80)
);

insert into queries values (1, 'oracle');
insert into queries values (2, 'larry or ellison');
insert into queries values (3, 'oracle and text');
insert into queries values (4, 'market share');

create index queryx on queries(query_string)
indextype is ctxsys.ctxrule;

select query_id from queries
where matches(query_string,
'Oracle announced that its market share in databases
increased over the last year.')>0

This query will return queries 1 (the word oracle appears in the document) and 4 (the phrase market share appears in the document), but not 2 (neither the word larry nor the word ellison appears, and not 3 (there is no text in the document, so it does not match the query).

Note that, in this example, the document was passed in as a string for simplicity. Typically, your document would be passed in a bind variable.

The document text used in a matches query can be VARCHAR2 or CLOB. It does not accept BLOB input, so you cannot match filtered documents directly. Instead, you must filter the binary content to CLOB using the AUTO_FILTER filter. For the following example, we make two assumptions: one, that the document data is in the bind variable :doc_blob; and, two, that we have already defined a policy, my_policy, that CTX_DOC.POLICY_FILTER can use. For example:

declare
doc_text clob;
begin
-- create a temporary CLOB to hold the document text
doc_text := dbms_lob.createtemporary(doc_text, TRUE, DBMS_LOB.SESSION);

-- create a simple policy for this example
ctx_ddl.create_preference(preference_name => 'fast_filter',
object_name       => 'AUTO_FILTER');
ctx_ddl.set_attribute(preference_name => 'fast_filter',
attribute_name    => 'OUTPUT_FORMATTING',
attribute_value   => 'FALSE');
ctx_ddl.create_policy(policy_name     => 'my_policy',
filter            => 'fast_filter);

-- call ctx_doc.policy_filter to filter the BLOB to CLOB data
ctx_doc.policy_filter('my_policy', :doc_blob, doc_text, FALSE);

-- now do the matches query using the CLOB version
for c1 in (select * from queries where matches(query_string, doc_text)>0)
loop
-- do what you need to do here
end loop;

dbms_lob.freetemporary(doc_text);
end;

The procedure CTX_DOC.POLICY_FILTER filters the BLOB into the CLOB data, because you need to get the text into a CLOB to enter a MATCHES query. It takes as one argument the name of a policy you have already created with CTX_DDL.CREATE_POLICY.

See Also:

Oracle Text Reference for information on CTX_DOC.POLICY_FILTER

If your file is text in the database character set, then you can create a BFILE and load it to a CLOB using the function DBMS_LOB.LOADFROMFILE, or you can use UTL_FILE to read the file into a temp CLOB locator.

If your file needs AUTO_FILTER filtering, then you can load the file into a BLOB instead, and call CTX_DOC.POLICY_FILTER, as previously shown.

See Also:

Classifying Documents in Oracle Text for more extended classification examples

MATCHES PL/SQL Example

The following example assumes that the table of queries profiles has a CTXRULE index associated with it. It also assumes that the table newsfeed contains a set of news articles to be categorized.

This example loops through the newsfeed table, categorizing each article using the MATCHES operator. The results are stored in the results table.

PROMPT  Populate the category table based on newsfeed articles
PROMPT
set serveroutput on;
declare
mypk   number;
mytitle varchar2(1000);
myarticles clob;
mycategory varchar2(100);
cursor doccur is select pk,title,articles from newsfeed;
cursor mycur is  select category from profiles where matches(rule, myarticles)>0;
cursor rescur is select category, pk, title from results order by category,pk;

begin
dbms_output.enable(1000000);
open doccur;
loop
fetch doccur into mypk, mytitle, myarticles;
exit when doccur%notfound;
open mycur;
loop
fetch mycur into mycategory;
exit when mycur%notfound;
insert into results values(mycategory, mypk, mytitle);
end loop;
close mycur;
commit;
end loop;
close doccur;
commit;

end;

The following example displays the categorized articles by category.

PROMPT  display the list of articles for every category
PROMPT
set serveroutput on;

declare
mypk   number;
mytitle varchar2(1000);
mycategory varchar2(100);
cursor catcur is select category from profiles order by category;
cursor rescur is select pk, title from results where category=mycategory order by pk;

begin
dbms_output.enable(1000000);
open catcur;
loop
fetch catcur into mycategory;
exit when catcur%notfound;
dbms_output.put_line('********** CATEGORY: '||mycategory||' *************');
open rescur;
loop
fetch rescur into mypk, mytitle;
exit when rescur%notfound;
dbms_output.put_line('**  ('||mypk||'). '||mytitle);
end loop;
close rescur;
dbms_output.put_line('**');
dbms_output.put_line('*******************************************************');
end loop;
close catcur;
end;

See Also:

Classifying Documents in Oracle Text for more extended classification examples

Word and Phrase Queries

A word query is a query on a word or phrase. For example, to find all the rows in your text table that contain the word dog, enter a query specifying dog as your query term.

You can enter word queries with both CONTAINS and CATSEARCH SQL operators. However, phrase queries are interpreted differently.

- CONTAINS Phrase Queries

- CATSEARCH Phrase Queries

CONTAINS Phrase Queries

If multiple words are contained in a query expression, separated only by blank spaces (no operators), the string of words is considered a phrase and Oracle Text searches for the entire string during a query.

For example, to find all documents that contain the phrase international law, enter your query with the phrase international law.

CATSEARCH Phrase Queries

With the CATSEARCH operator, the AND operator is inserted between words in phrases. For example, a query such as international law is interpreted as international AND law.

Querying Stopwords

Stopwords are words for which Oracle Text does not create an index entry. They are usually common words in your language that are unlikely to be searched on by themselves.

Oracle Text includes a default list of stopwords for your language. This list is called a stoplist. For example, in English, the words this and that are defined as stopwords in the default stoplist. You can modify the default stoplist or create new stoplists with the CTX_DDL package. You can also add stopwords after indexing with the ALTER INDEX statement.

You cannot query on a stopword by itself or on a phrase composed of only stopwords. For example, a query on the word this returns no hits when this is defined as a stopword.

You can query on phrases that contain stopwords as well as non-stopwords such as this boy talks to that girl. This is possible because the Oracle Text index records the position of stopwords even though it does not create an index entry for them.

When you include a stopword within your query phrase, the stopword matches any word. For example, the query:

'Jack was big'

matches phrases such as Jack is big and Jack grew big assuming was is a stopword. Note that this query matches grew, even though it is not a stopword.

ABOUT Queries and Themes

An ABOUT query is a query on a document theme. A document theme is a concept that is sufficiently developed in the text. For example, an ABOUT query on US politics might return documents containing information about US presidential elections and US foreign policy. Documents need not contain the exact phrase US politics to be returned.

During indexing, document themes are derived from the knowledge base, which is a hierarchical list of categories and concepts that represents a view of the world. Some examples of themes in the knowledge catalog are concrete concepts such as jazz music, football, or Nelson Mandela. Themes can also be abstract concepts such as happiness or honesty.

During indexing, the system can also identify and index document themes that are sufficiently developed in the document, but do not exist in the knowledge base.

You can augment the knowledge base to define concepts and terms specific to your industry or query application. When you do so, ABOUT queries are more precise for the added concepts.

ABOUT queries perform best when you create a theme component in your index. Theme components are created by default for English and French.

See Also:

Oracle Text Reference

Querying Stopthemes

Oracle Text enables you to query on themes with the ABOUT operator. A stoptheme is a theme that is not to be indexed. You can add and remove stopthemes with the CTX_DDL package. You can add stopthemes after indexing with the ALTER INDEX statement.

Query Expressions

A query expression is everything in between the single quotes in the text_query argument of the CONTAINS or CATSEARCH operator. What you can include in a query expression in a CONTAINS query is different from what you can include in a CATSEARCH operator.

- CONTAINS Operators

- CATSEARCH Operator

- MATCHES Operator

CONTAINS Operators

A CONTAINS query expression can contain query operators that enable logical, proximity, thesaural, fuzzy, and wildcard searching. Querying with stored expressions is also possible. Within the query expression, you can use grouping characters to alter operator precedence. This book refers to these operators as the CONTEXT grammar.

With CONTAINS, you can also use the ABOUT query to query document themes.

See Also:

"The CONTEXT Grammar"

CATSEARCH Operator

With the CATSEARCH operator, you specify your query expression with the text_query argument and your optional structured criteria with the structured_query argument. The text_query argument enables you to query words and phrases. You can use logical operations, such as logical and, or, and not. This book refers to these operators as the CTXCAT grammar.

If you want to use the much richer set of operators supported by the CONTEXT grammar, you can use the query template feature with CATSEARCH.

With structured_query argument, you specify your structured criteria. You can use the following SQL operations:

- =

- <=

- >=

- >

- <

- IN

- BETWEEN

You can also use ORDER BY clause to order your output.

See Also:

"The CTXCAT Grammar"

MATCHES Operator

Unlike CONTAINS and CATSEARCH, MATCHES does not take a query expression as input.

Instead, the MATCHES operator takes a document as input and finds all rows in a query (rule) table that match it. As such, you can use MATCHES to classify documents according to the rules they match.

See Also:

"Querying with MATCHES"

Case-Sensitive Searching

Oracle Text supports case-sensitivity for word and ABOUT queries.

- Word Queries

- ABOUT Queries

Word Queries

Word queries are not case-insensitive by default. This means that a query on the term dog returns the rows in your text table that contain the word dog, but not Dog, or DOG.

You can enable or disable case-sensitive searching with the MIXED_CASE attribute in your BASIC_LEXER index preference. With a case-sensitive index, your queries must be entered in exact case. For example, a query on Dog matches only documents with Dog. Documents with dog or DOG are not returned as hits.

To enable case-insensitive searching, set the MIXED_CASE attribute in your BASIC_LEXER index preference to NO.

Stopwords and Case-Sensitivity

If you have case-sensitivity enabled for word queries and you enter a query on a phrase containing stopwords and non-stopwords, then you must specify the correct case for the stopwords. For example, a query on the dog does not return text that contains The Dog, assuming that the is a stopword.

ABOUT Queries

ABOUT queries give the best results when your query is formulated with proper case. This is because the normalization of your query is based on the knowledge catalog which is case-sensitive. Attention to case is required especially for words that have different meanings depending on case, such as turkey the bird and Turkey the country.

However, you need not enter your query in exact case to obtain relevant results from an ABOUT query. The system does its best to interpret your query. For example, if you enter a query of ORACLE and the system does not find this concept in the knowledge catalog, the system might use Oracle as a related concept for look-up.

Query Feedback

Feedback information provides broader term, narrower term, and related term information for a specified query with a context index. You obtain this information programatically with the CTX_QUERY.HFEEDBACK procedure.

Broader term, narrower term, and related term information is useful for suggesting other query terms to the user in your query application.

The feedback information returned is obtained from the knowledge base and contains only those terms that are also in the index. This increases the chances that terms returned from HFEEDBACK produce hits over the currently indexed document set.

See Also:

Oracle Text Reference for more information about using CTX_QUERY.HFEEDBACK

Query Explain Plan

Explain plan information provides a graphical representation of the parse tree for a CONTAINS query expression. You can obtain this information programatically with the CTX_QUERY.EXPLAIN procedure.

Explain plan information tells you how a query is expanded and parsed without having the system execute the query. Obtaining explain information is useful for knowing the expansion for a particular stem, wildcard, thesaurus, fuzzy, soundex, or ABOUT query. Parse trees also show the following information:

- Order of execution

- ABOUT query normalization

- Query expression optimization

- Stop-word transformations

- Breakdown of composite-word tokens for supported languages

See Also:

Oracle Text Reference for more information about using CTX_QUERY.EXPLAIN

Using a Thesaurus in Queries

Oracle Text enables you to define a thesaurus for your query application.

Defining a custom thesaurus enables you to process queries more intelligently. Because users of your application might not know which words represent a topic, you can define synonyms or narrower terms for likely query terms. You can use the thesaurus operators to expand your query to include thesaurus terms.

See Also:

Working With a Thesaurus in Oracle Text

About Document Section Searching

Section searching enables you to narrow text queries down to sections within documents.

Section searching can be implemented when your documents have internal structure, such as HTML and XML documents. For example, you can define a section for the <H1> tag that enables you to query within this section using the WITHIN operator.

You can set the system to automatically create sections from XML documents.

You can also define attribute sections to search attribute text in XML documents.

Note:

Section searching is supported for only word queries with a CONTEXT index.

See Also:

Searching Document Sections in Oracle Text

Using Query Templates

Query templates are an alternative to the existing query languages. Rather than passing a query string to CONTAINS or CATSEARCH, you pass a structured document that contains the query string in a tagged element. Within this structured document, or query template, you can enable additional query features:

- Query Rewrite

- Query Relaxation

- Query Language

- Ordering By SDATA Sections

- Alternative and User-defined Scoring

- Alternative Grammar

Query Rewrite

Query applications sometimes parse end user queries, interpreting a query string in one or more ways using different operator combinations. For example, if a user enters a query of kukui nut, your application might enter the queries {kukui nut} and {kukui or nut} to increase recall.

The query rewrite feature enables you to submit a single query that expands the original query into the rewritten versions. The results are returned with no duplication.

You specify your rewrite sequences with the query template feature. The rewritten versions of the query are executed efficiently with a single call to CONTAINS or CATSEARCH.

The following template defines a query rewrite sequence. The query of {kukui nut} is rewritten as follows:

{kukui} {nut}

{kukui} ; {nut}

{kukui} AND {nut}

{kukui} ACCUM {nut}

The query rewrite template for these transformations is as follows:

select id from docs where CONTAINS (text,
'<query>
<textquery lang="ENGLISH" grammar="CONTEXT"> kukui nut
<progression>
<seq><rewrite>transform((TOKENS, "{", "}", " "))</rewrite></seq>
<seq><rewrite>transform((TOKENS, "{", "}", " ; "))</rewrite></seq>
<seq><rewrite>transform((TOKENS, "{", "}", "AND"))</rewrite></seq>
<seq><rewrite>transform((TOKENS, "{", "}", "ACCUM"))</rewrite></seq>
</progression>
</textquery>
<score datatype="INTEGER" algorithm="COUNT"/>
</query>')>0;

Query Relaxation

Query relaxation enables your application to execute the most restrictive version of a query first, progressively relaxing the query until the required number of hits are obtained.

For example, your application might search first on black pen and then the query is relaxed to black NEAR pen to obtain more hits.

The following query template defines a query relaxation sequence. The query of black pen is entered in sequence as the following:

{black} {pen}

{black} NEAR {pen}

{black} AND {pen}

{black} ACCUM {pen}

The query relaxation template for these transformations is as follows:

select id from docs where CONTAINS (text,
'<query>
<textquery lang="ENGLISH" grammar="CONTEXT">
<progression>
<seq>{black} {pen}</seq>
<seq>{black} NEAR {pen}</seq>
<seq>{black} AND {pen}</seq>
<seq>{black} ACCUM {pen}</seq>
</progression>
</textquery>
<score datatype="INTEGER" algorithm="COUNT"/>
</query>')>0;

Query hits are returned in this sequence with no duplication as long as the application needs results.

Query relaxation is most effective when your application needs the top-N hits to a query, which you can obtain with the DOMAIN_INDEX_SORT hint or in a PL/SQL cursor.

Using query templating to relax a query as such is more efficient than re-executing a query.

Query Language

When you use the MULTI_LEXER to index a column containing documents in different languages, you can specify which language lexer to use during querying. You do so using the lang parameter in the query template, which specifies the document-level lexer.

select id from docs where CONTAINS (text,
'<query><textquery lang="french">bon soir</textquery></query>')>0;

See Also:

Oracle Text Reference for information on LANGUAGE and lang with ALTER INDEX and document sublexer

Ordering By SDATA Sections

You can order the query results according to the content of SDATA sections using the <order> and <orderkey> elements of the query template.

In the following example, the first level of ordering is done on the SDATA section price, which is sorted in the ascending order. The second and third level of ordering is done by the SDATA section pub_date and score, both of which are sorted in the descending order.

select id from docs where CONTAINS (text, '
<query>
<textquery lang="ENGLISH" grammar="CONTEXT"> Oracle </textquery>
<score datatype="INTEGER" algorithm="COUNT"/>
<order>
<orderkey> SDATA(price) ASC </orderkey>
<orderkey> SDATA(pub_date) DESC </orderKey>
<orderkey> Score DESC </orderkey>
</order>
</query>', 1)>0;

Note:

You can add additional SDATA sections to an index without completely rebuilding the index. Refer to the ADD SDATA SECTION parameter string under ALTER INDEX in Oracle Text Reference.

See Also:

Oracle Text Reference for syntax of <order> and <orderkey> elements of the query template

Alternative and User-defined Scoring

You can use query templating to specify alternative scoring algorithms to use, other than the default, to customize how CONTAINS is scored, and to enable SDATA to be used as part of the scoring expressions. In this way, you can mathematically define the scoring expression using not only pre-defined scoring components, but also SDATA components.

With alternative user-defined scoring, you can:

- Specify the scoring expressions of terms by defining arithmetic expressions that define how the query should be scored, using

- predefined scoring algorithms: DISCRETE, OCCURRENCE, RELEVANCE, and COMPLETION;

- arithmetic operations: plus, minus, multiply, divide;

- arithmetic functions: ABS(n), finding the absolute value of n ; LOG(n), finding the base-10 logarithmic value of n;

- Numeric literals.

- Specify the scoring expressions at the term level.

- Specify terms that should not be taken into account when calculating the score.

- Specify how the score from child elements of OR and AND operators should be merged.

- Use SDATA that stores numeric or DATETIME values to affect the final score of the document.

The following example specifies an alternative scoring algorithm:

select id from docs where CONTAINS (text,
'<query>
<textquery grammar="CONTEXT" lang="english"> mustang  </textquery>
<score datatype="float" algorithm="DEFAULT"/>
</query>')>0

The following query templating example includes SDATA values as part of the final score:

select id from docs where CONTAINS (text,
'<query>
<textquery grammar="CONTEXT" lang="english"> mustang </textquery>
<score datatype="float" algorithm="DEFAULT" normalization_expr ="doc_score+SDATA(price)"/>
</query>')>0"

See Also:

"Using DEFINESCORE and DEFINEMERGE for User-defined Scoring"

Alternative Grammar

Query template enables you to use the CONTEXT grammar with CATSEARCH queries and vice-versa.

select id from docs where CONTAINS (text,
'<query>
<textquery grammar="CTXCAT">San Diego</textquery>
<score datatype="integer"/>
</query>')>0;

Query Analysis

Oracle Text enables you to create a log of queries and to analyze the queries it contains. For example, suppose you have an application that searches a database of large animals, and your analysis of its queries shows that users are continually searching for the word mouse; this analysis might induce you to rewrite your application so that a search for mouse redirects the user to a database of small animals instead of simply returning an unsuccessful search.

With query analysis, you can find out

- Which queries were made

- Which queries were successful

- Which queries were unsuccessful

- How many times each query was made

You can combine these factors in various ways, such as determining the 50 most frequent unsuccessful queries made by your application.

You start query logging with CTX_OUTPUT.START_QUERY_LOG. The query log will contain all queries made to all context indexes that the program is using until a CTX_OUTPUT.END_QUERY_LOG procedure is entered. Use CTX_REPORT.QUERY_LOG_SUMMARY to get a report of queries made.

See Also:

Oracle Text Reference for syntax and examples for these procedures

Other Query Features

In your query application, you can use other query features such as proximity searching. Table 4-1 lists some of these features.

Table 4-1 Other Oracle Text Query Features

Feature

Description

Implement With

Case Sensitive Searching

Enables you to search on words or phrases exactly as entered in the query. For example, a search on Roman returns documents that contain Roman and not roman.

BASIC_LEXER when you create the index

Base Letter Conversion

Queries words with or without diacritical marks such as tildes, accents, and umlauts. For example, with a Spanish base-letter index, a query of energía matches documents containing both energía and energia.

BASIC_LEXER when you create the index

Word Decompounding

(German and Dutch)

Enables searching on words that contain specified term as sub-composite.

BASIC_LEXER when you create the index

Alternate Spelling

(German, Dutch, and Swedish)

Searches on alternate spellings of words.

BASIC_LEXER when you create the index

Proximity Searching

Searches for words near one another.

NEAR operator when you enter the query

Stemming

Searches for words with same root as specified term.

$ operator at when you enter the query

Fuzzy Searching

Searches for words that have similar spelling to specified term.

FUZZY operator when you enter the query

Query Explain Plan

Generates query parse information.

CTX_QUERY.EXPLAIN PL/SQL procedure after you index

Hierarchical Query Feedback

Generates broader term, narrower term and related term information for a query.

CTX_QUERY.HFEEDBACK PL/SQL procedure after you index.

Browse index

Browses the words around a seed word in the index.

CTX_QUERY.BROWSE_WORDS PL/SQL after you index.

Count hits

Counts the number of hits in a query.

CTX_QUERY.COUNT_HITS PL/SQL procedure after you index.

Stored Query Expression

Stores the text of a query expression for later reuse in another query.

CTX_QUERY.STORE_SQE PL/SQL procedure after you index.

Thesaural Queries

Uses a thesaurus to expand queries.

Thesaurus operators such as SYN and BT as well as the ABOUT operator.

Use CTX_THES package to maintain thesaurus.

The CONTEXT Grammar

The CONTEXT grammar is the default grammar for CONTAINS. With this grammar, you can add complexity to your searches with operators. You use the query operators in your query expression. For example, the logical operator AND enables you to search for all documents that contain two different words. The ABOUT operator enables you to search on concepts.

You can also use the WITHIN operator for section searching, the NEAR operator for proximity searches, the stem, fuzzy, and thesaural operators for expanding a query expression.

With CONTAINS, you can also use the CTXCAT grammar with the query template feature.

The following sections describe some of the Oracle Text operators.

- ABOUT Query

- Logical Operators

- Section Searching and HTML and XML

- Proximity Queries with NEAR and NEAR_ACCUM Operators

- Fuzzy_ Stem_ Soundex_ Wildcard and Thesaurus Expansion Operators

- Using CTXCAT Grammar

- Stored Query Expressions

- Calling PL/SQL Functions in CONTAINS

- Optimizing for Response Time

- Counting Hits

- Using DEFINESCORE and DEFINEMERGE for User-defined Scoring

See Also:

Oracle Text Reference for complete information about using query operators

ABOUT Query

Use the ABOUT operator in English or French to query on a concept. The query string is usually a concept or theme that represents the idea to be searched on. Oracle Text returns the documents that contain the theme.

Word information and theme information are combined into a single index. To enter a theme query, your index must have a theme component which is created by default in English and French.

Enter a theme query using the ABOUT operator inside the query expression. For example, to retrieve all documents that are about politics, write your query as follows:

SELECT SCORE(1), title FROM news
WHERE CONTAINS(text, 'about(politics)', 1) > 0
ORDER BY SCORE(1) DESC;

See Also:

Oracle Text Reference for more information about using the ABOUT operator

Logical Operators

Logical operators such as AND or OR allow you to limit your search criteria in a number of ways. Table 4-2 describes some of these operators.

Table 4-2 Logical Operators

Operator

Symbol

Description

Example Expression

AND

&

Use the AND operator to search for documents that contain at least one occurrence of each of the query terms.

Score returned is the minimum of the operands.

'cats AND dogs'
'cats & dogs'

OR

|

Use the OR operator to search for documents that contain at least one occurrence of any of the query terms.

Score returned is the maximum of the operands.

'cats | dogs'
'cats OR dogs'

NOT

~

Use the NOT operator to search for documents that contain one query term and not another.

To obtain the documents that contain the term animals but not dogs, use the following expression:

'animals ~ dogs'

ACCUM

,

Use the ACCUM operator to search for documents that contain at least one occurrence of any of the query terms. The accumulate operator ranks documents according to the total term weight of a document.

The following query returns all documents that contain the terms dogs, cats and puppies giving the highest scores to the documents that contain all three terms:

'dogs, cats, puppies'

EQUIV

=

Use the EQUIV operator to specify an acceptable substitution for a word in a query.

The following example returns all documents that contain either the phrase alsatians are big dogs or German shepherds are big dogs:

'German shepherds=alsatians are big dogs'

Section Searching and HTML and XML

Section searching is useful when your document set is HTML or XML. For HTML, you can define sections using embedded tags and then use the WITHIN operator to search these sections.

For XML, you can have the system automatically create sections for you. You can query with the WITHIN operator or with the INPATH operator for path searching.

See Also:

Searching Document Sections in Oracle Text

Proximity Queries with NEAR and NEAR_ACCUM Operators

You can search for terms that are near to one another in a document with the NEAR operator.

For example, to find all the documents where dog is within 6 words of cat, enter the following query:

'near((dog, cat), 6)'

The NEAR_ACCUM operator combines the functionality of the NEAR operator with that of the ACCUM operator. Like NEAR, it returns terms that are within a given proximity of each other; however, if one term is not found, it ranks documents according to the frequency of the occurrence of the term that is found.

See Also:

Oracle Text Reference for more information about using the NEAR and NEAR_ACCUM operators

Fuzzy, Stem, Soundex, Wildcard and Thesaurus Expansion Operators

You can expand your queries into longer word lists with operators such as wildcard, fuzzy, stem, soundex, and thesaurus.

See Also:

- Oracle Text Reference for more information about using these operators

- "Is it OK to have many expansions in a query?"

Using CTXCAT Grammar

You can use the CTXCAT grammar in CONTAINS queries. To do so, use a query template specification in the text_query parameter of CONTAINS.

You might take advantage of the CTXCAT grammar when you need an alternative and simpler query grammar.

See Also:

Oracle Text Reference for more information about using these operators

Stored Query Expressions

You can use the procedure CTX_QUERY.STORE_SQE to store the definition of a query without storing any results. Referencing the query with the CONTAINS SQL operator references the definition of the query. In this way, stored query expressions make it easy for defining long or frequently used query expressions.

Stored query expressions are not attached to an index. When you call CTX_QUERY.STORE_SQE, you specify only the name of the stored query expression and the query expression.

The query definitions are stored in the Text data dictionary. Any user can reference a stored query expression.

- Defining a Stored Query Expression

- SQE Example

See Also:

Oracle Text Reference to learn more about the syntax of CTX_QUERY.STORE_SQE

Defining a Stored Query Expression

You define and use a stored query expression as follows:

1. Call CTX_QUERY.STORE_SQE to store the queries for the text column. With STORE_SQE, you specify a name for the stored query expression and a query expression.

2. Call the stored query expression in a query expression using the SQE operator. Oracle Text returns the results of the stored query expression in the same way it returns the results of a regular query. The query is evaluated at the time the stored query expression is called.

You can delete a stored query expression using REMOVE_SQE.

SQE Example

The following example creates a stored query expression called disaster that searches for documents containing the words tornado, hurricane, or earthquake:

begin
ctx_query.store_sqe('disaster', 'tornado | hurricane | earthquake');
end;

To execute this query in an expression, write your query as follows:

SELECT SCORE(1), title from news
WHERE CONTAINS(text, 'SQE(disaster)', 1) > 0
ORDER BY SCORE(1);

See Also:

Oracle Text Reference to learn more about the syntax of CTX_QUERY.STORE_SQE

Calling PL/SQL Functions in CONTAINS

You can call user-defined functions directly in the CONTAINS clause as long as the function satisfies the requirements for being named in a SQL statement. The caller must also have EXECUTE privilege on the function.

For example, assuming the function french returns the French equivalent of an English word, you can search on the French word for cat by writing:

SELECT SCORE(1), title from news
WHERE CONTAINS(text, french('cat'), 1) > 0
ORDER BY SCORE(1);

See Also:

Oracle Database SQL Language Reference for more information about creating user functions and calling user functions from SQL

Optimizing for Response Time

A CONTAINS query optimized for response time provides a fast solution for when you need the highest scoring documents from a hitlist.

The following example returns the first twenty hits to standard out. This example uses the FIRST_ROWS(n) hint and a cursor.

declare
cursor c is
select /*+ FIRST_ROWS(20) */ title, score(1) score
from news where contains(txt_col, 'dog', 1) > 0 order by score(1) desc;
begin
for c1 in c
loop
dbms_output.put_line(c1.score||':'||substr(c1.title,1,50));
exit when c%rowcount = 21;
end loop;
end;
/

Besides using query hints, there are other factors that can influence query response time such as:

- Collection of table statistics

- Memory allocation

- Sorting

- Presence of LOB columns in your base table

- Partitioning

- Parallelism

- The number term expansions in your query

See Also:

- "Frequently Asked Questions About Query Performance"

- "Frequently Asked Questions About Query Performance"

Counting Hits

To count the number of hits returned from a query with only a CONTAINS predicate, you can use CTX_QUERY.COUNT_HITS in PL/SQL or COUNT(*) in a SQL SELECT statement.

If you want a rough hit count, you can use CTX_QUERY.COUNT_HITS in estimate mode (EXACT parameter set to FALSE). With respect to response time, this is the fastest count you can get.

To count the number of hits returned from a query that contains a structured predicate, use the COUNT(*) function in a SELECT statement.

- SQL Count Hits Example

- Counting Hits with a Structured Predicate

- PL/SQL Count Hits Example

SQL Count Hits Example

To find the number of documents that contain the word oracle, enter the query with the SQL COUNT function as follows:

SELECT count(*) FROM news WHERE CONTAINS(text, 'oracle', 1) > 0;

Counting Hits with a Structured Predicate

To find the number of documents returned by a query with a structured predicate, use COUNT(*) as follows:

SELECT COUNT(*) FROM news WHERE CONTAINS(text, 'oracle', 1) > 0 and author = 'jones';

PL/SQL Count Hits Example

To find the number of documents that contain the word oracle, use COUNT_HITS as follows:

declare count number;
begin
count := ctx_query.count_hits(index_name => my_index, text_query => 'oracle', exact => TRUE);
dbms_output.put_line('Number of docs with oracle:');
dbms_output.put_line(count);
end;

See Also:

Oracle Text Reference to learn more about the syntax of CTX_QUERY.COUNT_HITS

Using DEFINESCORE and DEFINEMERGE for User-defined Scoring

The DEFINESCORE operator enables you to define how the score for a term or phrase is to be calculated. The DEFINEMERGE operator defines how to merge scores of child elements of AND and OR operators. You can also use the alternative scoring template with SDATA to affect the final scoring of the document.

See Also:

- "Alternative and User-defined Scoring" for information about the alternative scoring template

- Oracle Text Reference to learn more about the syntax of DEFINESCORE and DEFINEMERGE

The CTXCAT Grammar

The CTXCAT grammar is the default grammar for CATSEARCH. This grammar supports logical operations such as AND and OR as well as phrase queries.

The CATSEARCH query operators have the following syntax:

Table 4-3 CATSEARCH Query Operator Syntax

Operation

Syntax

Description of Operation

Logical AND

a b c

Returns rows that contain a, b and c.

Logical OR

a | b | c

Returns rows that contain a, b, or c.

Logical NOT

a - b

Returns rows that contain a and not b.

hyphen with no space

a-b

Hyphen treated as a regular character.

For example, if the hyphen is defined as skipjoin, words such as web-site treated as the single query term website.

Likewise, if the hyphen is defined as a printjoin, words such as web-site treated as web site with the space in the CTXCAT query language.

" "

"a b c"

Returns rows that contain the phrase "a b c".

For example, entering "Sony CD Player" means return all rows that contain this sequence of words.

( )

(A B) | C

Parentheses group operations. This query is equivalent to the CONTAINS query (A &B) | C.

You can use the CONTEXT grammar in CATSEARCH queries. To do so, use a query template specification in the text_query parameter.

You might use the CONTAINS grammar as such when you need to enter proximity, thesaurus, or ABOUT queries with a CTXCAT index.

See Also:

Oracle Text Reference for more information about using these operators

5 Presenting Documents in Oracle Text

Oracle Text provides various methods for presenting documents in results for query applications. This chapter describes document presentation.

This chapter contains the following topics:

- Highlighting Query Terms

- Obtaining Part-of-Speech Information for a Document

- Obtaining Lists of Themes_ Gists_ and Theme Summaries

- Document Presentation and Highlighting

Highlighting Query Terms

In Oracle Text query applications, you can present selected documents with query terms highlighted for text queries or with themes highlighted for ABOUT queries.

You can generate three types of output associated with highlighting:

- A marked-up version of the document

- Query offset information for the document

- A concordance of the document, in which occurrences of the query term are returned with their surrounding text

This section contains the following topics:

- Text highlighting

- Theme Highlighting

- CTX_DOC Highlighting Procedures

Text highlighting

For text highlighting, you supply the query, and Oracle Text highlights words in the document that satisfy the query. You can obtain plain-text or HTML highlighting.

Theme Highlighting

For ABOUT queries, the CTX_DOC procedures highlight and mark up words or phrases that best represent the ABOUT query.

CTX_DOC Highlighting Procedures

These are the highlighting procedures in CTX_DOC:

- CTX_DOC.MARKUP and CTX_DOC.POLICY_MARKUP

- CTX_DOC.HIGHLIGHT and CTX_DOC.POLICY_HIGHLIGHT

- CTX_DOC.SNIPPET and CTX_DOC.POLICY_SNIPPET

The POLICY and non-POLICY versions of the procedures are equivalent, except that the POLICY versions do not require an index.

Note:

SNIPPET can also be generated using the Result Set Interface. See Oracle Text Reference for information on CTX_QUERY.RESULT_SET

This section contains these topics:

- Markup Procedure

- Highlight Procedure

- Concordance

Markup Procedure

The CTX_DOC.MARKUP and CTX_DOC.POLICY_MARKUP procedures take a document reference and a query, and return a marked-up version of the document. The output can be either marked-up plaintext or marked-up HTML. For example, you might specify that a marked-up document be returned with the query term surrounded by angle brackets (<<<tansu>>>) or HTML (<b>tansu</b>).

CTX_DOC.MARKUP and CTX_DOC.POLICY_MARKUP are equivalent, except that CTX_DOC.POLICY_MARKUP does not require an index.

You can customize the markup sequence for HTML navigation.

CTX_DOC.MARKUP Example

The following example is taken from the Web application described in CONTEXT Query Application. The procedure showDoc takes an HTML document and a query, creates the highlight markup—in this case, the query term will display in red—and outputs the result to an in-memory buffer. It then uses htp.print to display it in the browser.

procedure showDoc (p_id in varchar2, p_query in varchar2) is

v_clob_selected   CLOB;
v_read_amount     integer;
v_read_offset     integer;
v_buffer          varchar2(32767);
v_query           varchar(2000);
v_cursor          integer;

begin
htp.p('<html><title>HTML version with highlighted terms</title>');
htp.p('<body bgcolor="#ffffff">');
htp.p('<b>HTML version with highlighted terms</b>');

begin
ctx_doc.markup (index_name => 'idx_search_table',
textkey    => p_id,
text_query => p_query,
restab     => v_clob_selected,
starttag   => '<i><font color=red>',
endtag     => '</font></i>');

v_read_amount := 32767;
v_read_offset := 1;
begin
loop
dbms_lob.read(v_clob_selected,v_read_amount,v_read_offset,v_buffer);
htp.print(v_buffer);
v_read_offset := v_read_offset + v_read_amount;
v_read_amount := 32767;
end loop;
exception
when no_data_found then
null;
end;

exception
when others then
null; --showHTMLdoc(p_id);
end;
end showDoc;
end;
/
show errors
set define on

See Also:

Oracle Text Reference for more information about CTX_DOC.MARKUP and CTX_DOC.POLICY_SNIPPET

Highlight Procedure

CTX_DOC.HIGHLIGHT and CTX_DOC.POLICY_HIGHLIGHT take a query and a document and return offset information for the query in either plaintext or HTML formats. This offset information can be used to write your own custom routines for displaying documents.

CTX_DOC.HIGHLIGHT and CTX_DOC.POLICY_HIGHLIGHT are equivalent, except that CTX_DOC.POLICY_HIGHLIGHT does not require an index.

With offset information, you can display a highlighted version of document as desired. For example, you can display the document with different font types or colors rather than using the standard plain text markup obtained from CTX_DOC.MARKUP.

See Also:

Oracle Text Reference for more information about using CTX_DOC.HIGHLIGHT and CTX_DOC.POLICY_HIGHLIGHT

Concordance

CTX_DOC.SNIPPET and CTX_DOC.POLICY_SNIPPET produce a concordance of the document, in which occurrences of the query term are returned with their surrounding text. This result is sometimes known as Key Word in Context, or KWIC, because instead of returning the entire document (with or without the query term highlighted), it returns the query term in text fragments, allowing a user to see it in context. You can control the way the query term is highlighted in the returned fragments.

CTX_DOC.SNIPPET and CTX_DOC.POLICY_SNIPPET are equivalent, except that CTX_DOC.POLICY_SNIPPET does not require an index. CTX_DOC.POLICY_SNIPPET and CTX_DOC.SNIPPET include two new attributes: radius and max_length. The radius attribute specifies the approximate desired length of each segment. Whereas, max_length puts an upper bound on the length of the sum of all segments.

See Also:

Oracle Text Reference for more information about CTX_DOC.SNIPPET and CTX_DOC.POLICY_SNIPPET

Obtaining Part-of-Speech Information for a Document

The CTX_DOC package contains procedures to create policies for obtaining part-of-speech information for a given document. This is described under POLICY_NOUN_PHRASES in Oracle Text Reference and POLICY_PART_OF_SPEECH in Oracle Text Reference.

Obtaining Lists of Themes, Gists, and Theme Summaries

The following table describes lists of themes, gists, and theme summaries.

Table 5-1 Lists of Themes, Gists, and Theme Summaries

Output Type

Description

List of Themes

A list of the main concepts of a document.

You can generate list of themes where each theme is a single word or phrase or where each theme is a hierarchical list of parent themes.

Gist

Text in a document that best represents what the document is about as a whole.

Theme Summary

Text in a document that best represents a given theme in the document.

To obtain this output, you use procedures in the CTX_DOC supplied package. With this package, you can do the following:

- Identify documents by ROWID in addition to primary key

- Store results in-memory for improved performance

Lists of Themes

A list of themes is a list of the main concepts in a document. Use the CTX_DOC.THEMES procedure to generate lists of themes.

See Also:

Oracle Text Reference to learn more about the command syntax for CTX_DOC.THEMES

The following In-Memory Theme example generates the top 10 themes for document 1 and stores them in an in-memory table called the_themes. The example then loops through the table to display the document themes.

declare
the_themes ctx_doc.theme_tab;

begin
ctx_doc.themes('myindex','1',the_themes, numthemes=>10);
for i in 1..the_themes.count loop
dbms_output.put_line(the_themes(i).theme||':'||the_themes(i).weight);
end loop;
end;

The following example create a Result Table Theme.

create table ctx_themes (query_id number,
theme varchar2(2000),
weight number);

To obtain a list of themes where each element in the list is a single theme, enter the following:

begin
ctx_doc.themes('newsindex','34','CTX_THEMES',1,full_themes => FALSE);
end;

To obtain a list of themes where each element in the list is a hierarchical list of parent themes, enter the following:

begin
ctx_doc.themes('newsindex','34','CTX_THEMES',1,full_themes => TRUE);
end;

Gist and Theme Summary

A gist is the text of a document that best represents what the document is about as a whole. A theme summary is the text of a document that best represents a single theme in the document.

Use the procedure CTX_DOC.GIST to generate gists and theme summaries. You can specify the size of the gist or theme summary when you call the procedure.

- In-Memory Gist

- Result Table Gists

- Theme Summary

See Also:

Oracle Text Reference to learn about the command syntax for CTX_DOC.GIST

In-Memory Gist

The following example generates a nondefault size generic gist of at most 10 paragraphs. The result is stored in memory in a CLOB locator. The code then de-allocates the returned CLOB locator after using it.

declare
gklob clob;
amt number := 40;
line varchar2(80);

begin
ctx_doc.gist('newsindex','34','gklob',1,glevel => 'P',pov => 'GENERIC',       numParagraphs => 10);
-- gklob is NULL when passed-in, so ctx-doc.gist will allocate a temporary
-- CLOB for us and place the results there.

dbms_lob.read(gklob, amt, 1, line);
dbms_output.put_line('FIRST 40 CHARS ARE:'||line);
-- have to de-allocate the temp lob
dbms_lob.freetemporary(gklob);
end;

Result Table Gists

To create a gist table:

create table ctx_gist (query_id  number,
pov       varchar2(80),
gist      CLOB);

The following example returns a default sized paragraph level gist for document 34:

begin
ctx_doc.gist('newsindex','34','CTX_GIST',1,'PARAGRAPH', pov =>'GENERIC');
end;

The following example generates a nondefault size gist of ten paragraphs:

begin
ctx_doc.gist('newsindex','34','CTX_GIST',1,'PARAGRAPH', pov =>'GENERIC',        numParagraphs => 10);
end;

The following example generates a gist whose number of paragraphs is ten percent of the total paragraphs in document:

begin
ctx_doc.gist('newsindex','34','CTX_GIST',1, 'PARAGRAPH', pov =>'GENERIC', maxPercent => 10);
end;

Theme Summary

The following example returns a theme summary on the theme of insects for document with textkey 34. The default Gist size is returned.

begin
ctx_doc.gist('newsindex','34','CTX_GIST',1, 'PARAGRAPH', pov => 'insects');
end;

Document Presentation and Highlighting

Typically, a query application enables the user to view the documents returned by a query. The user selects a document from the hit list and then the application presents the document in some form.

With Oracle Text, you can display a document in different ways. For example, you can present documents with query terms highlighted. Highlighted query terms can be either the words of a word query or the themes of an ABOUT query in English.

You can also obtain gist (document summary) and theme information from documents with the CTX_DOC PL/SQL package.

Table 5-2 describes the different output you can obtain and which procedure to use to obtain each type.

Table 5-2 CTX_DOC Output

Output

Procedure

Plain text version, no highlights

CTX_DOC.FILTER

HTML version of document, no highlights

CTX_DOC.FILTER

Highlighted document, plain text version

CTX_DOC.MARKUP

Highlighted document, HTML version

CTX_DOC.MARKUP

Highlight offset information for plain text version

CTX_DOC.HIGHLIGHT

Highlight offset information for HTML version

CTX_DOC.HIGHLIGHT

Theme summaries and gist of document.

CTX_DOC.GIST

List of themes in document.

CTX_DOC.THEMES

See Also:

Oracle Text Reference

Figure 5-1 shows an original document to which we can apply highlighting, gisting, and theme extraction in the following sections.

- Highlighting Example

- Document List of Themes Example

- Gist Example

Figure 5-1 Sample Document for Highlighting, Gisting, and Theme Extraction

Highlighting Example

Figure 5-2 is a screen shot of a query application presenting the document shown in Figure 5-1 with the query term pet highlighted. This output was created using the text query application described in CONTEXT Query Application.

Figure 5-2 Pet Highlighted in Pet Magnet Document

Document List of Themes Example

Figure 5-3 is a screen shot of a query application presenting a list of themes for the document shown in Figure 5-1. This output was created using the text query application described in CONTEXT Query Application.

Figure 5-3 Query Application Displaying Document Themes

Gist Example

Figure 5-4 is a screen shot of a query application presenting a gist of the document shown in Figure 5-1. This output was created using the text query application produced described in CONTEXT Query Application.

Figure 5-4 Query Application Presenting Document Gist

6 Classifying Documents in Oracle Text

This chapter includes the following topics:

- Overview of Document Classification

- Classification Applications

- Classification Solutions

- Rule-Based Classification

- Supervised Classification

- Unsupervised Classification (Clustering)

- Unsupervised Classification (Clustering) Example

Overview of Document Classification

A major problem facing businesses and institutions today is that of information overload. Sorting out useful documents from documents that are not of interest challenges the ingenuity and resources of both individuals and organizations.

One way to sift through numerous documents is to use keyword search engines. However, keyword searches have limitations. One major drawback is that keyword searches do not discriminate by context. In many languages, a word or phrase may have multiple meanings, so a search may result in many matches that are not on the desired topic. For example, a query on the phrase river bank might return documents about the Hudson River Bank & Trust Company, because the word bank has two meanings.

An alternative strategy is to have human beings sort through documents and classify them by content, but this is not feasible for very large volumes of documents.

Oracle Text offers various approaches to document classification. Under rule-based classification, you write the classification rules yourself. With supervised classification, Oracle Text creates classification rules based on a set of sample documents that you pre-classify. Finally, with unsupervised classification (also known as clustering), Oracle Text performs all the steps, from writing the classification rules to classifying the documents, for you.

Classification Applications

Oracle Text enables you to build document classification applications. A document classification application performs some action based on document content. Actions include assigning category IDs to a document for future lookup or sending a document to a user. The result is a set or stream of categorized documents. Figure 6-1 illustrates how the classification process works.

Oracle Text enables you to create document classification applications in different ways. This chapter defines a typical classification scenario and shows how you can use Oracle Text to build a solution.

Figure 6-1 Overview of a Document Classification Application

Classification Solutions

Oracle Text enables you to classify documents in the following ways:

- Rule-Based Classification. In rule-based classification, you group your documents together, decide on categories, and formulate the rules that define those categories; these rules are actually query phrases. You then index the rules and use the MATCHES operator to classify documents.
Advantage: Rule-based classification is very accurate for small document sets. Results are always based on what you define, because you write the rules.

Disadvantages: Defining rules can be tedious for large document sets with many categories. As your document set grows, you may need to write correspondingly more rules.

- Supervised Classification. This method is similar to rule-based classification, but the rule writing step is automated with CTX_CLS.TRAIN. CTX_CLS.TRAIN formulates a set of classification rules from a sample set of pre-classified documents that you provide. As with rule-based classification, you use MATCHES operator to classify documents.
Oracle Text offers two versions of supervised classification, one using the RULE_CLASSIFIER preference and one using the SVM_CLASSIFIER preference. These are discussed in "Supervised Classification".

Advantage: Rules are written for you automatically. This is useful for large document sets.

Disadvantages:

- You must assign documents to categories before generating the rules.

- Rules may not be as specific or accurate as those you write yourself.

- Unsupervised Classification (Clustering). All steps from grouping your documents to writing the category rules are automated with CTX_CLS.CLUSTERING. Oracle Text statistically analyzes your document set and correlates them with clusters according to content.
Advantages:

- You do not need to provide either the classification rules or the sample documents as a training set.

- Helps to discover patterns and content similarities in your document set that you might overlook.
In fact, you can use unsupervised classification when you do not have a clear idea of rules or classifications. One possible scenario is to use unsupervised classification to provide an initial set of categories, and to subsequently build on these through supervised classification.

Disadvantages:

- Clustering might result in unexpected groupings, because the clustering operation is not user-defined, but based on an internal algorithm.

- You do not see the rules that create the clusters.

- The clustering operation is CPU-intensive and can take at least the same time as indexing.

Rule-Based Classification

Rule-based classification (sometimes called "simple classification") is the basic way of creating an Oracle Text classification application.

The basic steps for rule-based classification are as follows. Specific steps are explored in greater detail in the example.

1. Create a table for the documents to be classified, and populate it.

2. Create a rule table (also known as a category table). The rule table consists of categories that you name, such as "medicine" or "finance," and the rules that sort documents into those categories.
These rules are actually queries. For example, you might define the "medicine" category as consisting of documents that include the words "hospital," "doctor," or "disease," so you would set up a rule of the form "hospital OR doctor OR disease." See "CTXRULE Parameters and Limitations" for information on which operators are allowed for queries.

3. Create a CTXRULE index on the rule table.

4. Classify the documents.

Rule-based Classification Example

In this example, we gather news articles on different subjects and then classify them.

Once our rules are created, we can index them and then use the MATCHES statement to classify documents.

Perform the following steps to classify documents.

- Step 1 Create schema

- Step 2 Load Documents with SQLLDR

- Step 3 Create Categories

- Step 4 Create the CTXRULE index

- Step 5 Classify Documents

Step 1 Create schema

We create the tables to store the data. The news_table stores the documents to be classified. The news_categories table stores the categories and rules that define our categories. The news_id_cat table stores the document ids and their associated categories after classification.

create table news_table (
tk number primary key not null,
title varchar2(1000),
text clob);

create table news_categories (
queryid  number primary key not null,
category varchar2(100),
query    varchar2(2000));

create table news_id_cat (
tk number,
category_id number);

Step 2 Load Documents with SQLLDR

In this step, we load the HTML news articles into the news_table using the SQLLDR program. The filenames and titles are read from loader.dat.

LOAD DATA
INFILE 'loader.dat'
INTO TABLE news_table
REPLACE
FIELDS TERMINATED BY ';'
(tk         INTEGER EXTERNAL,
title      CHAR,
text_file  FILLER CHAR,
text       LOBFILE(text_file) TERMINATED BY EOF)

Step 3 Create Categories

In this step, we define our categories and write the rules for each of our categories.

The defined categories are: Asia, Europe, Africa, Middle East, Latin America, United States, Conflicts, Finance, Technology, Consumer Electronics, World Politics, U.S. Politics, Astronomy, Paleontology, Health, Natural Disasters, Law, and Music News.

A rule is a query that selects documents for the category. For example, the category 'Asia' has a rule of 'China or Pakistan or India or Japan'. We insert our rules in the news_categories table as follows:

insert into news_categories values
(1,'United States','Washington or George Bush or Colin Powell');

insert into news_categories values
(2,'Europe','England or Britain or Germany');

insert into news_categories values
(3,'Middle East','Israel or Iran or Palestine');

insert into news_categories values(4,'Asia','China or Pakistan or India or Japan');

insert into news_categories values(5,'Africa','Egypt or Kenya or Nigeria');

insert into news_categories values
(6,'Conflicts','war or soliders or military or troops');

insert into news_categories values(7,'Finance','profit or loss or wall street');
insert into news_categories values
(8,'Technology','software or computer or Oracle
or Intel or IBM or Microsoft');

insert into news_categories values
(9,'Consumer electronics','HDTV or electronics');

insert into news_categories values
(10,'Latin America','Venezuela or Colombia
or Argentina or Brazil or Chile');

insert into news_categories values
(11,'World Politics','Hugo Chavez or George Bush
or Tony Blair or Saddam Hussein or United Nations');

insert into news_categories values
(12,'US Politics','George Bush or Democrats or Republicans
or civil rights or Senate or White House');

insert into news_categories values
(13,'Astronomy','Jupiter or Earth or star or planet or Orion
or Venus or Mercury or Mars or Milky Way
or Telescope or astronomer
or NASA or astronaut');

insert into news_categories values
(14,'Paleontology','fossils or scientist
or paleontologist or dinosaur or Nature');

insert into news_categories values
(15,'Health','stem cells or embryo or health or medical
or medicine or World Health Organization or AIDS or HIV
or virus or centers for disease control or vaccination');

insert into news_categories values
(16,'Natural Disasters','earthquake or hurricane or tornado');

insert into news_categories values
(17,'Law','abortion or Supreme Court or illegal
or legal or legislation');

insert into news_categories values
(18,'Music News','piracy or anti-piracy
or Recording Industry Association of America
or copyright or copy-protection or CDs
or music or artist or song');

commit;

Step 4 Create the CTXRULE index

In this step, we create a CTXRULE index on our news_categories query column.

create index news_cat_idx on news_categories(query)
indextype is ctxsys.ctxrule;

Step 5 Classify Documents

To classify the documents, we use the CLASSIFIER.THIS PL/SQL procedure (a simple procedure designed for this example), which scrolls through the news_table, matches each document to a category, and writes the categorized results into the news_id_cat table.

create or replace package classifier asprocedure this;end;/

show errors

create or replace package body classifier as

procedure this
is
v_document    clob;
v_item        number;
v_doc         number;
begin

for doc in (select tk, text from news_table)
loop
v_document := doc.text;
v_item := 0;
v_doc  := doc.tk;
for c in (select queryid, category from news_categories
where matches(query, v_document) > 0 )
loop
v_item := v_item + 1;
insert into news_id_cat values (doc.tk,c.queryid);
end loop;
end loop;

end this;

end;
/
show errors
exec classifier.this

CTXRULE Parameters and Limitations

The following considerations apply to indexing a CTXRULE index.

- If the SVM_CLASSIFIER classifier is used, then you may use the BASIC_LEXER, CHINESE_LEXER, JAPANESE_LEXER, or KOREAN_MORPH_LEXER lexers. If SVM_CLASSIFIER is not used, only the BASIC_LEXER lexer type may be used for indexing your query set. (See Oracle Text Reference for more on lexer and classifier preferences.)

- Filter, memory, datastore, and [no]populate parameters are not applicable to index type CTXRULE.

- The CREATE INDEX storage clause is supported for creating the index on the queries.

- Wordlists are supported for stemming operations on your query set.

- Queries for CTXRULE are similar to those of CONTAINS queries. Basic phrasing ("dog house") is supported, as are the following CONTAINS operators: ABOUT, AND, NEAR, NOT, OR, STEM, WITHIN, and THESAURUS. Section groups are supported for using the MATCHES operator to classify documents. Field sections are also supported; however, CTXRULE does not directly support field queries, so you must use a query rewrite on a CONTEXT query.

See Also:

"Creating a CTXRULE Index"

Supervised Classification

With supervised classification, you employ the CTX_CLS.TRAIN procedure to automate the rule writing step. CTX_CLS.TRAIN uses a training set of sample documents to deduce classification rules. This is the major advantage over rule-based classification, in which you must write the classification rules.

However, before you can run the CTX_CLS.TRAIN procedure, you must manually create categories and assign each document in the sample training set to a category.

See Also:

Oracle Text Reference for more information on CTX_CLS.TRAIN

When the rules are generated, you index them to create a CTXRULE index. You can then use the MATCHES operator to classify an incoming stream of new documents.

You may choose between two different classification algorithms for supervised classification:

- Decision Tree Supervised Classification
The advantage of Decision Tree classification is that the generated rules are easily observed (and modified). See "Decision Tree Supervised Classification Example".

- SVM-Based Supervised Classification
This method uses the Support Vector Machine (SVM) algorithm for creating rules. The advantage of SVM-based classification is that it is often more accurate than Decision Tree classification. The disadvantage is that it generates binary rules, so the rules themselves are opaque. See "SVM-Based Supervised Classification Example".

Decision Tree Supervised Classification

To use Decision Tree classification, you set the preference argument of CTX_CLS.TRAIN to RULE_CLASSIFIER.

This form of classification uses a decision tree algorithm for creating rules. Generally speaking, a decision tree is a method of deciding between two (or more, but usually two) choices. In document classification, the choices are "the document matches the training set" or "the document does not match the training set."

A decision tree has a set of attributes that can be tested. In this case, these include:

- words from the document

- stems of words from the document (as an example, the stem of running is run)

- themes from the document (if themes are supported for the language in use)

The learning algorithm in Oracle Text builds one or more decision trees for each category provided in the training set. These decision trees are then coded into queries suitable for use by a CTXRULE index. As a trivial example, if one category is provided with a training document that consists of "Japanese beetle" and another category with a document reading "Japanese currency," the algorithm may create decision trees based on the words "Japanese," "beetle," and "currency," and classify documents accordingly.

The decision trees include the concept of confidence. Each rule that is generated is allocated a percentage value that represents the accuracy of the rule, given the current training set. In trivial examples, this accuracy is almost always 100%, but this merely represents the limitations of the training set. Similarly, the rules generated from a trivial training set may seem to be less than what you might expect, but these are sufficient to distinguish the different categories given the current training set.

The advantage of the Decision Tree method is that it can generate rules that are easily inspected and modified by a human. Using Decision Tree classification makes sense when you want to the computer to generate the bulk of the rules, but you want to fine tune them afterward by editing the rule sets.

Decision Tree Supervised Classification Example

The following SQL example steps through creating your document and classification tables, classifying the documents, and generating the rules. It then goes on to generate rules with CTX_CLS.TRAIN.

Rules are then indexed to create CTXRULE index and new documents are classified with MATCHES.

The general steps for supervised classification can be broken down as follows:

- Create the Category Rules

- Index Rules to Categorize New Documents

Create the Category Rules

The CTX_CLS.TRAIN procedure requires an input training document set. A training set is a set of documents that have already been assigned a category.

Perform the following steps to create the category rules.

1. Create and populate a training document table
Create and load a table of training documents. This example uses a simple set; three concern fast food and three concern computers.

create table docs (
doc_id number primary key,
doc_text   clob);

insert into docs values
(1, 'MacTavishes is a fast-food chain specializing in burgers, fries and -
shakes. Burgers are clearly their most important line.');
insert into docs values
(2, 'Burger Prince are an up-market chain of burger shops, who sell burgers -
and fries in competition with the likes of MacTavishes.');
insert into docs values
(3, 'Shakes 2 Go are a new venture in the low-cost restaurant arena,
specializing in semi-liquid frozen fruit-flavored vegetable oil products.');
insert into docs values
(4, 'TCP/IP network engineers generally need to know about routers,
firewalls, hosts, patch cables networking etc');
insert into docs values
(5, 'Firewalls are used to protect a network from attack by remote hosts,
generally across TCP/IP');

2. Create category tables, category descriptions and ids

----------------------------------------------------------------------------

-- Create category tables
-- Note that "category_descriptions" isn't really needed for this demo -
-- it just provides a descriptive name for the category numbers in
-- doc_categories
----------------------------------------------------------------------------

create table category_descriptions (
cd_category    number,
cd_description varchar2(80));

create table doc_categories (
dc_category    number,
dc_doc_id      number,
primary key (dc_category, dc_doc_id))
organization index;

-- descriptons for categories

insert into category_descriptions values (1, 'fast food');
insert into category_descriptions values (2, 'computer networking');

3. Assign each document to a category
In this case, the fast food documents all go into category 1, and the computer documents into category 2.

insert into doc_categories values (1, 1);
insert into doc_categories values (1, 2);
insert into doc_categories values (1, 3);
insert into doc_categories values (2, 4);
insert into doc_categories values (2, 5);

4. Create a CONTEXT index to be used by CTX_CLS.TRAIN
Create an Oracle Text preference for the index. This enables us to experiment with the effects of turning themes on and off:

exec ctx_ddl.create_preference('my_lex', 'basic_lexer');
exec ctx_ddl.set_attribute    ('my_lex', 'index_themes', 'no');
exec ctx_ddl.set_attribute    ('my_lex', 'index_text',   'yes');

create index docsindex on docs(doc_text) indextype is ctxsys.context
parameters ('lexer my_lex');

5. Create the rules table
Create the table that will be populated by the generated rules.

create table rules(
rule_cat_id     number,
rule_text       varchar2(4000),
rule_confidence number
);

6. Call CTX_CLS.TRAIN procedure to generate category rules
Now call the CTX_CLS.TRAIN procedure to generate some rules. Note all the arguments are the names of tables, columns or indexes previously created in this example. The rules table now contains the rules, which you can view.

begin
ctx_cls.train(
index_name => 'docsindex',
docid      => 'doc_id',
cattab     => 'doc_categories',
catdocid   => 'dc_doc_id',
catid      => 'dc_category',
restab     => 'rules',
rescatid   => 'rule_cat_id',
resquery   => 'rule_text',
resconfid  => 'rule_confidence'
);
end;
/

7. Fetch the generated rules, viewed by category
Fetch the generated rules. For convenience's sake, the rules table is joined with category_descriptions so we can see to which category each rule applies:

select cd_description, rule_confidence, rule_text from rules,
category_descriptions where cd_category = rule_cat_id;

Index Rules to Categorize New Documents

Once the rules are generated, you can test them by first indexing them and then using MATCHES to classify new documents. The process is as follows:

1. Index the rules to create the CTXRULE index
Use CREATE INDEX to create the CTXRULE index on the previously generated rules:

create index rules_idx on rules (rule_text) indextype is ctxsys.ctxrule;

2. Test an incoming document using MATCHES

set serveroutput on;

declare
incoming_doc clob;
begin
incoming_doc
:= 'I have spent my entire life managing restaurants selling burgers';
for c in
( select distinct cd_description from rules, category_descriptions
where cd_category = rule_cat_id
and matches (rule_text, incoming_doc) > 0) loop
dbms_output.put_line('CATEGORY: '||c.cd_description);
end loop;
end;
/

SVM-Based Supervised Classification

The second method we can use for training purposes is known as Support Vector Machine (SVM) classification. SVM is a type of machine learning algorithm derived from statistical learning theory. A property of SVM classification is the ability to learn from a very small sample set.

Using the SVM classifier is much the same as using the Decision Tree classifier, with the following differences.

- The preference used in the call to CTX_CLS.TRAIN should be of type SVM_CLASSIFIER instead of RULE_CLASSIFIER. (If you do not want to modify any attributes, you can use the predefined preference CTXSYS.SVM_CLASSIFIER.)

- The CONTEXT index on the table does not have to be populated; that is, you can use the NOPOPULATE keyword. The classifier uses it only to find the source of the text, by means of datastore and filter preferences, and to determine how to process the text, through lexer and sectioner preferences.

- The table for the generated rules must have (as a minimum) these columns:

cat_id      number,
type        number,
rule        blob;

As you can see, the generated rule is written into a BLOB column. It is therefore opaque to the user, and unlike Decision Tree classification rules, it cannot be edited or modified. The trade-off here is that you often get considerably better accuracy with SVM than with Decision Tree classification.

With SVM classification, allocated memory has to be large enough to load the SVM model; otherwise, the application built on SVM will incur an out-of-memory error. Here is how to calculate the memory allocation:

Minimum memory request (in bytes) = number of unique categories x number of features
example: (value of MAX_FEATURES attributes) x 8

If necessary to meet the minimum memory requirements, either:

- increase SGA memory (if in shared server mode)

- increase PGA memory (if in dedicated server mode)

SVM-Based Supervised Classification Example

The following example uses SVM-based classification. It uses essentially the same steps as the Decision Tree example. Some differences between the examples are as follows:

- In this example, we set the SVM_CLASSIFIER preference with CTX_DDL.CREATE_PREFERENCE rather than setting it in CTX_CLS.TRAIN. (You can do it either way.)

- In this example, our category table includes category descriptions, unlike the category table in the Decision Tree example. (You can do it either way.)

- CTX_CLS.TRAIN takes fewer arguments than in the Decision Tree example, as rules are opaque to the user.

Perform the following steps to create a SVM-based supervised classification.

1. Create and populate the training document table

create table doc (id number primary key, text varchar2(2000));
insert into doc values(1,'1 2 3 4 5 6');
insert into doc values(2,'3 4 7 8 9 0');
insert into doc values(3,'a b c d e f');
insert into doc values(4,'g h i j k l m n o p q r');
insert into doc values(5,'g h i j k s t u v w x y z');

2. Create and populate the category table

create table testcategory (
doc_id number,
cat_id number,
cat_name varchar2(100)
);
insert into testcategory values (1,1,'number');
insert into testcategory values (2,1,'number');
insert into testcategory values (3,2,'letter');
insert into testcategory values (4,2,'letter');
insert into testcategory values (5,2,'letter');

3. Create the CONTEXT index on the document table
In this case, we create the index without populating.

create index docx on doc(text) indextype is ctxsys.context
parameters('nopopulate');

4. Set the SVM_CLASSIFIER
This can also be done in CTX.CLS_TRAIN.

exec ctx_ddl.create_preference('my_classifier','SVM_CLASSIFIER');
exec ctx_ddl.set_attribute('my_classifier','MAX_FEATURES','100');

5. Create the result (rule) table

create table restab (
cat_id number,
type number(3) not null,
rule blob
);

6. Perform the training

exec ctx_cls.train('docx', 'id','testcategory','doc_id','cat_id',
'restab','my_classifier');

7. Create a CTXRULE index on the rules table

exec ctx_ddl.create_preference('my_filter','NULL_FILTER');
create index restabx on restab (rule)
indextype is ctxsys.ctxrule
parameters ('filter my_filter classifier my_classifier');

Now we can classify two unknown documents:

select cat_id, match_score(1) from restab
where matches(rule, '4 5 6',1)>50;

select cat_id, match_score(1) from restab
where matches(rule, 'f h j',1)>50;

drop table doc;
drop table testcategory;
drop table restab;
exec ctx_ddl.drop_preference('my_classifier');
exec ctx_ddl.drop_preference('my_filter');

Unsupervised Classification (Clustering)

With Rule-Based Classification, you write the rules for classifying documents yourself. With Supervised Classification, Oracle Text writes the rules for you, but you must provide a set of training documents that you pre-classify. With unsupervised classification (also known as clustering), you do not even have to provide a training set of documents.

Clustering is performed with the CTX_CLS.CLUSTERING procedure. CTX_CLS.CLUSTERING creates a hierarchy of document groups, known as clusters, and, for each document, returns relevancy scores for all leaf clusters.

For example, suppose that you have a large collection of documents concerning animals. CTX_CLS.CLUSTERING might create one leaf cluster about dogs, another about cats, another about fish, and a fourth cluster about bears. (The first three might be grouped under a node cluster concerning pets.) Suppose further that you have a document about one breed of dogs, such as chihuahuas. CTX_CLS.CLUSTERING would assign the dog cluster to the document with a very high relevancy score, while the cat cluster would be assigned with a lower score and the fish and bear clusters with still lower scores. When scores for all clusters have been assigned to all documents, an application can then take action based on the scores.

As noted in "Decision Tree Supervised Classification", attributes used for determining clusters may consist of simple words (or tokens), word stems, and themes (where supported).

CTX_CLS.CLUSTERING assigns output to two tables (which may be in-memory tables):

- A document assignment table showing how similar the document is to each leaf cluster. This information takes the form of document identification, cluster identification, and a similarity score between the document and a cluster.

- A cluster description table containing information about what a generated cluster is about. This table contains cluster identification, cluster description text, a suggested cluster label, and a quality score for the cluster.

CTX_CLS.CLUSTERING employs a K-MEAN algorithm to perform clustering. Use the KMEAN_CLUSTERING preference to determine how CTX_CLS.CLUSTERING works.

See Also:

Oracle Text Reference for more information on cluster types and hierarchical clustering

Unsupervised Classification (Clustering) Example

The following SQL example creates a small collection of documents in the collection table and creates a CONTEXT index. It then creates a document assignment and cluster description table, which are populated with a call to the CLUSTERING procedure. The output would then be viewed with a select statement:

set serverout on

/* collect document into a table */
create table collection (id number primary key, text varchar2(4000));
insert into collection values (1, 'Oracle Text can index any document or textual content.');
insert into collection values (2, 'Ultra Search uses a crawler to access documents.');
insert into collection values (3, 'XML is a tag-based markup language.');
insert into collection values (4, 'Oracle Database 11g XML DB treats XML
as a native datatype in the database.');
insert into collection values (5, 'There are three Text index types to cover
all text search needs.');
insert into collection values (6, 'Ultra Search also provides API
for content management solutions.');

create index collectionx on collection(text)
indextype is ctxsys.context parameters('nopopulate');

/* prepare result tables, if you omit this step, procedure will create table automatically */
create table restab (
docid NUMBER,
clusterid NUMBER,
score NUMBER);

create table clusters (
clusterid NUMBER,
descript varchar2(4000),
label varchar2(200),
sze   number,
quality_score number,
parent number);

/* set the preference */
exec ctx_ddl.drop_preference('my_cluster');
exec ctx_ddl.create_preference('my_cluster','KMEAN_CLUSTERING');
exec ctx_ddl.set_attribute('my_cluster','CLUSTER_NUM','3');

/* do the clustering */
exec ctx_output.start_log('my_log');
exec ctx_cls.clustering('collectionx','id','restab','clusters','my_cluster');
exec ctx_output.end_log;

See Also:

Oracle Text Reference for CTX_CLS.CLUSTERING syntax and examples

7 Tuning Oracle Text

Oracle Text provides ways to improve your query and indexing performance.

This chapter contains the following topics:

- Optimizing Queries with Statistics

- Optimizing Queries for Response Time

- Optimizing Queries for Throughput

- Composite Domain Index (CDI) in Oracle Text

- Performance Tuning with CDI

- Solving Index and Query Bottlenecks Using Tracing

- Using Parallel Queries

- Tuning Queries with Blocking Operations

- Frequently Asked Questions About Query Performance

- Frequently Asked Questions About Indexing Performance

- Frequently Asked Questions About Updating the Index

Optimizing Queries with Statistics

Query optimization with statistics uses the collected statistics on the tables and indexes in a query to select an execution plan that can process the query in the most efficient manner. As a general rule, Oracle recommends that you collect statistics on your base table if you are interested in improving your query performance. Optimizing with statistics enables a more accurate estimation of the selectivity and costs of the CONTAINS predicate and thus a better execution plan.

The optimizer attempts to choose the best execution plan based on the following parameters:

- The selectivity on the CONTAINS predicate

- The selectivity of other predicates in the query

- The CPU and I/O costs of processing the CONTAINS predicates

The following topics discuss how to use statistics with the extensible query optimizer.

- Collecting Statistics

- Query Optimization with Statistics Example

- Re-Collecting Statistics

- Deleting Statistics

Note:

Importing and exporting of statistics on domain indexes, including Oracle Text indexes, is not supported with the DBMS_STATS package. For more information on importing and exporting statistics, see the Oracle Database PL/SQL Packages and Types Reference.

See Also:

Oracle Text Reference for information on the CONTAINS query operator

Collecting Statistics

By default, Oracle Text uses the cost-based optimizer (CBO) to determine the best execution plan for a query.

To enable the optimizer to better estimate costs, you can calculate the statistics on the table you query as follows:

ANALYZE TABLE <table_name> COMPUTE STATISTICS;

Alternatively, you can estimate the statistics on a sample of the table as follows:

ANALYZE TABLE <table_name> ESTIMATE STATISTICS 1000 ROWS;

or

ANALYZE TABLE <table_name> ESTIMATE STATISTICS 50 PERCENT;

You can also collect statistics in parallel with the DBMS_STATS.GATHER_TABLE_STATS procedure:

begin

DBMS_STATS.GATHER_TABLE_STATS('owner', 'table_name',
estimate_percent=>50,
block_sample=>TRUE,
degree=>4) ;

end  ;

These statements collect statistics on all the objects associated with table_name, including the table columns and any indexes (b-tree, bitmap, or Text domain) associated with the table.

To re-collect the statistics on a table, enter the ANALYZE statement as many times as necessary or use the DBMS_STATS package.

By collecting statistics on the Text domain index, the cost-based optimizer in Oracle Database is able to perform the following tasks:

- Estimate the selectivity of the CONTAINS predicate

- Estimate the I/O and CPU costs of using the Text index, that is, the cost of processing the CONTAINS predicate using the domain index

- Estimate the I/O and CPU costs of each invocation of CONTAINS

Knowing the selectivity of a CONTAINS predicate is useful for queries that contain more than one predicate, such as in structured queries. This way the cost-based optimizer can better decide whether to use the domain index to evaluate CONTAINS or to apply the CONTAINS predicate as a post filter.

See Also:

- Oracle Database SQL Language Reference for more information about the ANALYZE statement

- Oracle Database PL/SQL Packages and Types Reference for information about DBMS_STATS package

Query Optimization with Statistics Example

The following structured query provides an example for optimizing statistics.

select score(1) from tab where contains(txt, 'freedom', 1)  > 0 and author = 'King' and year > 1960;

Assume the author column is of type VARCHAR2 and the year column is of type NUMBER. Assume that there is a b-tree index on the author column.

Also assume that the structured author predicate is highly selective with respect to the CONTAINS predicate and the year predicate. That is, the structured predicate (author = 'King') returns a much smaller number of rows with respect to the year and CONTAINS predicates individually, say 5 rows returned versus 1000 and 1500 rows respectively.

In this situation, Oracle Text can execute this query more efficiently by first doing a b-tree index range scan on the structured predicate (author = 'King'), followed by a table access by rowid, and then applying the other two predicates to the rows returned from the b-tree table access.

Note:

When statistics are not collected for a Text index, the cost-based optimizer assumes low selectivity and index costs for the CONTAINS predicate.

Re-Collecting Statistics

After synchronizing your index, you can re-collect statistics on a single index to update the cost estimates.

If your base table has been re-analyzed before the synchronization, it is sufficient to analyze the index after the synchronization without re-analyzing the entire table.

To do so, enter any of the following statements:

ANALYZE INDEX <index_name> COMPUTE STATISTICS;

or

ANALYZE INDEX <index_name> ESTIMATE STATISTICS SAMPLE 50 PERCENT;

Deleting Statistics

You can delete the statistics associated with a table by issuing:

ANALYZE TABLE <table_name> DELETE STATISTICS;

You can delete statistics on one index by issuing the following statement:

ANALYZE INDEX <index_name> DELETE STATISTICS;

Optimizing Queries for Response Time

By default, Oracle Text optimizes queries for throughput. This results in queries returning all rows in shortest time possible.

However, in many cases, especially in a Web application scenario, queries must be optimized for response time, when you are only interested in obtaining the first few hits of a potentially large hitlist in the shortest time possible.

The following sections describe some ways to optimize CONTAINS queries for response time:

- Other Factors that Influence Query Response Time

- Improved Response Time with FIRST_ROWS(n) Hint for ORDER BY Queries

- Improved Response Time Using the DOMAIN_INDEX_SORT Hint

- Improved Response Time using Local Partitioned CONTEXT Index

- Improved Response Time with Local Partitioned Index for Order by Score

- Improved Response Time with Query Filter Cache

- Improved Response Time using BIG_IO Option of CONTEXT Index

- Improved Response Time using SEPARATE_OFFSETS Option of CONTEXT Index

- Improved Response Time using STAGE_ITAB Option of CONTEXT Index

Other Factors that Influence Query Response Time

There are other factors that can influence query response time such as:

- Collection of table statistics

- Memory allocation

- Sorting

- Presence of LOB columns in your base table

- Partitioning

- Parallelism

- The number term expansions in your query

See Also:

"Frequently Asked Questions About Query Performance"

Improved Response Time with FIRST_ROWS(n) Hint for ORDER BY Queries

When you need the first rows of an ORDER BY query, Oracle recommends that you use the cost-based FIRST_ROWS(n) hint.

Note:

As the FIRST_ROWS(n) hint is cost-based, Oracle recommends that you collect statistics on your tables before you use this hint.

You use the FIRST_ROWS(n) hint in cases where you want the first number (n) of rows in the shortest possible time. For example, consider the following PL/SQL block that uses a cursor to retrieve the first 10 hits of a query and uses the FIRST_ROWS(n) hint to optimize the response time:

declare
cursor c is

select /*+ FIRST_ROWS(10) */ article_id from articles_tab
where contains(article, 'Omophagia')>0 order by pub_date desc;

begin

for i in c
loop
insert into t_s values(i.pk, i.col);
exit when c%rowcount > 11;
end loop;

end;
/

The cursor c is a SELECT statement that returns the rowids that contain the word omophagia in sorted order. The code loops through the cursor to extract the first 10 rows. These rows are stored in the temporary table t_s.

With the FIRST_ROWS(n) hint, the optimizer instructs the Text index to return rowids in score-sorted order when the cost of returning the top-N hits is lower.

Without the hint, Oracle Database sorts the rowids after the Text index has returned all the rows in unsorted order that satisfy the CONTAINS predicate. Retrieving the entire result set this way takes time.

Because only the first 10 hits are needed in this query, using the hint results in better performance.

Note:

Use the FIRST_ROWS(n) hint when you need only the first few hits of a query. When you need the entire result set, do not use this hint as it might result in poor performance.

Improved Response Time Using the DOMAIN_INDEX_SORT Hint

You can also optimize for response time using the related DOMAIN_INDEX_SORT hint. Like FIRST_ROWS(n), when queries are optimized for response time, Oracle Text returns the first rows in the shortest time possible.

For example, you can use this hint as follows

select /*+ DOMAIN_INDEX_SORT */ pk, score(1), col from ctx_tab
where contains(txt_col, 'test', 1) > 0 order by score(1) desc;

However, this hint is only rule-based. This means that Oracle Text always chooses the index which satisfies the ORDER BY clause. This might result in sub-optimal performance for queries in which the CONTAINS clause is very selective. In these cases, Oracle recommends that you use the FIRST_ROWS(n) hint, which is fully cost-based.

Improved Response Time using Local Partitioned CONTEXT Index

Partitioning your data and creating local partitioned indexes can improve your query performance. On a partitioned table, each partition has its own set of index tables. Effectively, there are multiple indexes, but the results from each are combined as necessary to produce the final result set.

You create the CONTEXT index using the LOCAL keyword as follows:

CREATE INDEX index_name ON table_name (column_name)
INDEXTYPE IS ctxsys.context
PARAMETERS ('...')
LOCAL

With partitioned tables and indexes, you can improve performance of the following types of queries:

- Range Search on Partition Key Column

- ORDER BY Partition Key Column

Range Search on Partition Key Column

This is a query that restricts the search to a particular range of values on a column that is also the partition key. For example, consider a query on a date range:

SELECT storyid FROM storytab WHERE CONTAINS(story, 'oliver')>0 and pub_date BETWEEN '1-OCT-93' AND '1-NOV-93';

If the date range is quite restrictive, it is very likely that the query can be satisfied by only looking in a single partition.

ORDER BY Partition Key Column

This is a query that requires only the first n hits, and that the ORDER BY clause names the partition key. Consider an ORDER BY query on a price column to fetch the first 20 hits such as:

SELECT * FROM (

SELECT itemid FROM item_tab WHERE CONTAINS(item_desc, 'cd player')
>0 ORDER BY price)
WHERE ROWNUM < 20;

In this example, with the table partitioned by price, the query might only need to get hits from the first partition to satisfy the query.

Improved Response Time with Local Partitioned Index for Order by Score

Using the DOMAIN_INDEX_SORT hint on a local partitioned index might result in poor performance, especially when you order by score. This is because all hits to the query across all partitions must be obtained before the results can be sorted.

You can work around this by using an inline view when you use the DOMAIN_INDEX_SORT hint. Specifically, you can use the DOMAIN_INDEX_SORT hint to improve query performance on a local partitioned index under the following conditions:

- The text query itself including the order by SCORE() clause is expressed as an in-line view.

- The text query inside the in-line view contains the DOMAIN_INDEX_SORT hint.

- The query on the in-line view has ROWNUM predicate limiting number of rows to fetch from the view.

For example, if you have the following text query and local text index created on a partitioned table doc_tab:

select doc_id, score(1) from doc_tab
where contains(doc, 'oracle', 1)>0
order by score(1) desc;

and you are only interested in fetching top 20 rows, you can rewrite the query to

select * from
(select /*+ DOMAIN_INDEX_SORT */ doc_id, score(1) from doc_tab
where contains(doc, 'oracle', 1)>0 order by score(1) desc)
where rownum < 21;

See Also:

Oracle Database SQL Language Reference for more information about the EXPLAIN PLAN statement

Improved Response Time with Query Filter Cache

Oracle Text provides a cache layer called the query filter cache that can be used to cache the query results. The query filter cache is sharable across queries. Thus, the cached query results can be reused by multiple queries, improving the query response time.

The ctxfiltercache operator should be used to specify which query results to cache. The following example uses the ctxfiltercache operator to store the results of the common_predicate query in the cache:

select * from docs where contains(txt, 'ctxfiltercache((common_predicate), FALSE)')>0;

In the following example, the cached results of the common_predicate query are reused by the new_query query, thus improving the query response time.

select * from docs where contains(txt, 'new_query & ctxfiltercache((common_predicate), FALSE)')>0;

Note:

- You can specify the size of the query filter cache using the basic storage attribute query_filter_cache_size

- The view ctx_filter_cache_statistics provides various statistics about the query filter cache

See Also:

Oracle Text Reference for more information about:

- ctxfiltercache operator

- query_filter_cache_size basic storage attribute

- ctx_filter_cache_statistics view

Improved Response Time using BIG_IO Option of CONTEXT Index

Oracle Text provides the BIG_IO option for improving the query performance for the CONTEXT indexes that extensively use IO operations. The query performance improvement is mainly for data stored on rotating disks, and not for data stored on solid state disks.

A CONTEXT index with the BIG_IO option enabled creates token type pairs with one LOB (large object datatype) for each unique token text. Thus, tokens with the same text but different token types correspond to different rows in the $I table.

The indexes with the BIG_IO option enabled should have the token LOBs created as SecureFile LOBs. In the SecureFile lobs, the data is stored sequentially in multiple blocks. This improves the response time of the queries, as the queries can now perform longer sequential reads instead of performing many short reads.

Note:

Using SecureFiles requires the COMPATIBLE setting to be 11.0 or higher. In addition, the LOB must be created on an automatic segment space management (ASSM) tablespace. When migrating from the existing text indexes to SecureFiles, an ASSM tablespace should be used. To help in migrating the existing indexes to SecureFiles lobs, ALTER INDEX REBUILD is extended to provide the replacement of storage preferences that only affect the $I table without performing reindex.

To create a CONTEXT index with the BIG_IO index option, first create a basic storage preference by setting the value of its BIG_IO storage attribute to YES, and then specify this storage preference while creating the CONTEXT index.

The following example creates a basic storage preference mystore and sets the value of its BIG_IO storage attribute to YES:

exec ctx_ddl.create_preference('mystore', 'BASIC_STORAGE');
exec ctx_ddl.set_attribute('mystore', 'BIG_IO', 'YES');

To disable the BIG_IO option, update the existing storage preference (mystore) by setting the value of its BIG_IO storage attribute to NO, and then rebuild the index.

exec ctx_ddl.set_attribute('mystore', 'BIG_IO', 'NO');
alter index idx rebuild('replace storage mystore');

WARNING:

Do not use replace metadata operation to disable the BIG_IO index option, as it can leave the index in an inconsistent state.

To enable the BIG_IO option for a partitioned index without rebuilding the index, modify the basic storage preference by setting the value of its BIG_IO storage attribute to YES, replace the global index metadata using ctx_ddl.replace_index_metadata, and then call optimize_index in REBUILD mode for each of the partitions of the partitioned index table.

The following example enables the BIG_IO option for the partitioned index idx:

exec ctx_ddl.set_attribute('mystore', 'BIG_IO', 'YES');
exec ctx_ddl.replace_index_metadata('idx', 'replace storage mystore');
exec ctx_ddl.optimize_index('idx', 'rebuild', part_name=>'part1');

Note:

If a procedure modifies the existing index tables with only the BIG_IO option enabled, then it will not result in reindexing of the data.

Note:

Since the BIG_IO index option performs longer sequential reads, the queries that use the BIG_IO index option require a large program global area (PGA) memory.

Improved Response Time using SEPARATE_OFFSETS Option of CONTEXT Index

Oracle Text provides the SEPARATE_OFFSETS option for improving the query performance for the CONTEXT indexes that extensively use IO operations, and whose queries are mainly single-word or Boolean queries.

The SEPARATE_OFFSETS option creates a different postings list structure for the tokens of type TEXT. Instead of interspersing docids, frequencies, info-length (length of the offsets information), and the offsets in the postings list, the SEPARATE_OFFSETS option stores all the docids and the frequencies together at the beginning of the postings list, and all the info-lengths and the offsets at the end of the postings list. The header at the beginning of the posting contains the information about the boundary points between the docids and the offsets. This separation of the docids and the offsets reduces the time for the queries to read the data, thus improving the query response time.

The performance of the SEPARATE_OFFSETS option is best realized when it is used in conjunction with the BIG_IO option, and is used for the tokens with very long posting.

To create a CONTEXT index with the SEPARATE_OFFSETS index option, first create a basic storage preference by setting the value of its SEPARATE_OFFSETS storage attribute to T, and then specify this storage preference while creating the CONTEXT index.

The following example creates a basic storage preference mystore and sets the value of its SEPARATE_OFFSETS storage attribute to T:

exec ctx_ddl.create_preference('mystore', 'BASIC_STORAGE');
exec ctx_ddl.set_attribute('mystore', 'SEPARATE_OFFSETS', 'T');

To disable the SEPARATE_OFFSETS option, update the existing storage preference (mystore) by setting the value of its SEPARATE_OFFSETS storage attribute to F, and then rebuild the index.

exec ctx_ddl.set_attribute('mystore', 'SEPARATE_OFFSETS', 'F');
alter index idx rebuild('replace storage mystore');

WARNING:

Do not use replace metadata operation to disable the SEPARATE_OFFSETS index option, as it can leave the index in an inconsistent state.

To enable the SEPARATE_OFFSETS option for a partitioned index without rebuilding the index, modify the basic storage preference by setting the value of its SEPARATE_OFFSETS storage attribute to T, replace the global index metadata using ctx_ddl.replace_index_metadata, and then call optimize_index in REBUILD mode for each of the partitions of the partitioned index table.

The following example enables the SEPARATE_OFFSETS option for the partitioned index idx:

exec ctx_ddl.set_attribute('mystore', 'SEPARATE_OFFSETS', 'T');
exec ctx_ddl.replace_index_metadata('idx', 'replace storage mystore');
exec ctx_ddl.optimize_index('idx', 'rebuild', part_name=>'part1');

Note:

If a procedure modifies the existing index tables with only the SEPARATE_OFFSETS option enabled, then it will not result in reindexing of the data.

Improved Response Time using STAGE_ITAB Option of CONTEXT Index

Oracle Text provides the STAGE_ITAB option for improving the query performance for the CONTEXT indexes that extensively use DML operations for near real-time indexing.

When the STAGE_ITAB index option is not used, whenever a new document is added to the CONTEXT index, SYNC_INDEX is called to make the documents searchable. This creates new rows in the $I table, thus increasing the fragmentation in the $I table. This leads to the deterioration of the query performance.

When the STAGE_ITAB index option is enabled, the information about the new documents is stored in the $G staging table, and not in the $I table. This ensures that the $I table does not get fragmented, and thus not deteriorating the query performance.

When the STAGE_ITAB index option is enabled, the $H b-tree index is also created on the $G table. The $G table and $H b-tree index are equivalent to the $I table and $X b-tree index.

Use the MERGE optimization mode to optimize the rows present in the $G table and move them to the $I table.

Note:

The $G table is stored in the KEEP pool. You should allocate sufficient KEEP pool memory for the STAGE_ITAB query option to provide improved query performance.

To create a CONTEXT index with the STAGE_ITAB index option, first create a basic storage preference by setting the value of its STAGE_ITAB storage attribute to YES, and then specify this storage preference while creating the CONTEXT index.

The following example creates a basic storage preference mystore and sets the value of its STAGE_ITAB storage attribute to YES:

exec ctx_ddl.create_preference('mystore', 'BASIC_STORAGE');
exec ctx_ddl.set_attribute('mystore', 'STAGE_ITAB', 'YES');

You can also enable the STAGE_ITAB index option for an existing non-partitioned CONTEXT index by using the rebuild option of the ALTER INDEX statement.

alter index IDX rebuild parameters('replace storage mystore');

To disable the STAGE_ITAB option for a non-partitioned CONTEXT index, update the existing storage preference (mystore) by setting the value of its STAGE_ITAB storage attribute to NO, and then rebuild the index.

exec ctx_ddl.set_attribute('mystore', 'STAGE_ITAB', 'NO');
alter index idx rebuild('replace storage mystore');

This operation runs the optimization process using the MERGE optimization mode and then drops the $G table.

The rebuild option of the ALTER INDEX statement does not work with the partitioned CONTEXT index for enabling and disabling the STAGE_ITAB option.

The following example enables the STAGE_ITAB option for the partitioned CONTEXT index idx:

alter index idx parameters('add stage_itab');

The following example disables the STAGE_ITAB option for the partitioned CONTEXT index idx:

alter index idx parameters('remove stage_itab');

Note:

You also need to specify the BASIC_STORAGE preferences g_index_clause and g_table_clause for using the STAGE_ITAB index option for a CONTEXT index. See Oracle Text Reference for more information about BASIC_STORAGE.

Optimizing Queries for Throughput

Optimizing a query for throughput returns all hits in the shortest time possible. This is the default behavior.

The following sections describe how you can explicitly optimize for throughput.

- CHOOSE and ALL ROWS Modes

- FIRST_ROWS(n) Mode

CHOOSE and ALL ROWS Modes

By default, queries are optimized for throughput under the CHOOSE and ALL_ROWS modes. When queries are optimized for throughput, Oracle Text returns all rows in the shortest time possible.

FIRST_ROWS(n) Mode

In FIRST_ROWS(n) mode, the optimizer in Oracle Database optimizes for fast response time by having the Text domain index return score-sorted rows, if possible. This is the default behavior when you use the FIRST_ROWS(n) hint.

If you want to optimize for better throughput under FIRST_ROWS(n), you can use the DOMAIN_INDEX_NO_SORT hint. Better throughput means you are interested in getting all the rows to a query in the shortest time.

The following example achieves better throughput by not using the Text domain index to return score-sorted rows. Instead, Oracle Text sorts the rows after all the rows that satisfy the CONTAINS predicate are retrieved from the index:

select /*+ FIRST_ROWS(10) DOMAIN_INDEX_NO_SORT */ pk, score(1), col from ctx_tab
where contains(txt_col, 'test', 1) > 0 order by score(1) desc;

See Also:

Oracle Database SQL Tuning Guide for more information about the query optimizer and using hints such as FIRST_ROWS(n) and CHOOSE

Composite Domain Index (CDI) in Oracle Text

The Composite Domain Index feature of the Extensibility Framework in Oracle Database enables structured columns to be indexed by Oracle Text. Therefore, both text and one or more structured criteria can be satisfied by one single Oracle Text index row source. Performance for the following types of query are improved:

- Text query with structured criteria in the SQL WHERE clause.

- Text query with structured ORDER BY criteria.

- Combination of both of the previous two query types.

As with concatenated b-tree indexes or bitmap indexes, applications will experience slow-down in DML performance as the number of FILTER BY and ORDER BY columns increases. Where SCORE-sort push-down is optimized for response time, the structured sort or combination of SCORE and structured sort push-down are also optimized for response time, and not for throughput. However, using DOMAIN_INDEX_SORT or FIRST_ROWS(n) hints to force the sort to be pushed into CDI while fetching the entire hitlist may result in poor query response time.

Performance Tuning with CDI

Support for mapping a FILTER BY column to MDATA enables query performance to be optimized for equality searches by restricting supported functionality of RANGE and LIKE. However, mapping a FILTER BY column to MDATA is not recommended if the FILTER BY column contains sequential values, or has very high cardinality. Doing so can result in a very long and narrow $I table and reduced $X performance. One example of such a sequential column might be one that uses DATE stamp. For such sequential columns, mapping to SDATA is recommended.

The following hints can be used to push or not push the SORT and FILTER BY predicates into the CDI:

- DOMAIN_INDEX_SORT. The query optimizer will try to push the applicable sorting criteria into the specified composite domain index.

- DOMAIN_INDEX_NO_SORT. The query optimizer will try NOT to push sorting criteria into the specified composite domain index.

- DOMAIN_INDEX_FILTER(table name index name). The query optimizer will try to push the applicable FILTER BY predicate(s) into the specified composite domain index.

- DOMAIN_INDEX_NO_FILTER(table name index name). The query optimizer will not try to push the applicable FILTER BY predicate(s) into the specified composite domain index.

Note:

The domain_index_filter hint does not force the query optimizer to use CDI. Instead, if the cost-based optimizer chooses to use the CDI, then it should also push the filter predicate into the index. To force the query optimizer to choose CDI index, you additionally need to use the INDEX hint.

Example 7-1 Performance Tuning a Text Query with CDI Hints

The following example performs an optimized query on the table books.

SELECT bookid, pub_date, source FROM
(SELECT /*+ domain_index_sort domain_index_filter(books books_ctxcdi) */ bookid, pub_date, source
FROM books
WHERE CONTAINS(text, 'aaa',1)>0 AND bookid >= 80
ORDER BY PUB_DATE desc nulls last, SOURCE asc  nulls last, score(1) desc)
WHERE rownum < 20;

Solving Index and Query Bottlenecks Using Tracing

Oracle Text includes a tracing facility that enables you to identify bottlenecks in indexing and querying.

Oracle Text provides a set of predefined traces. Each trace is identified by a unique number. There is also a symbol in CTX_OUTPUT for this number.

Each trace measures a specific numeric quantity—for instance, the number of $I rows selected during text queries.

Traces are cumulative counters, so usage is as follows:

1. The user enables a trace.

2. The user performs one or more operations. Oracle Text measures activities and accumulates the results in the trace.

3. The user retrieves the trace value, which is the total value across all operations done in step 2.

4. The user resets the trace to 0.

5. The user starts over at Step 2.

So, for instance, if in step 2 the user runs two queries, and query 1 selects 15 rows from $I, and query 2 selects 17 rows from $I, then in step 3 the value of the trace would be 32 (15 + 17).

Traces are associated with a session—they can measure operations that take place within a single session, and, conversely, cannot make measurements across sessions.

During parallel sync or optimize, the trace profile will be copied to the slave sessions if and only if tracing is currently enabled. Each slave will accumulate its own traces and implicitly write all trace values to the slave logfile before termination.

See Also:

Oracle Text Reference

Using Parallel Queries

In general, parallel queries are optimal for DSS, OLAP, or analytical systems with large data collection, multiple CPUs with a low number of concurrent users, or parallelized across Oracle Real Application Clusters (Oracle RAC) nodes.

Oracle Text supports parallel queries as follows:

- Parallel Queries on a Local Context Index

- Parallelizing Queries Across Oracle RAC Nodes

Parallel Queries on a Local Context Index

Parallel query refers to the parallelized processing of a local CONTEXT index. Based on the parallel degree of the index and various system attributes, Oracle determines the number of parallel query slaves to be spawned to process the index. Each parallel query slave processes one or more index partitions. This is the default query behavior for local indexes created in parallel.

However, for heavily loaded systems with high numbers of concurrent users, query throughput will generally be worse with parallel query because top-N hits can usually be satisfied by the first few partitions, if the query is run serially. For example, typical top-N text queries with an ORDER BY partition key column, such as:

select * from (
select story_id from stories_tab where contains(...)>0 order by
publication_date desc)
where rownum <= 10;

will generally perform worse with a parallel query.

You can disable parallel querying after a parallel index operation with an ALTER INDEX statement as follows:

Alter index <text index name> NOPARALLEL;
Alter index <text index name> PARALLEL 1;

You can also enable or increase the parallel degree by specifying:

Alter index <text index name> parallel < parallel degree >;

Parallelizing Queries Across Oracle RAC Nodes

Oracle Real Application Clusters (Oracle RAC) provides an excellent solution for improving query throughput. If you can get good performance from Oracle Text with a light query load, then you can expect to get excellent scalability from Oracle RAC as the query load increases.

Further improvements in Oracle Text performance in an Oracle RAC environment may be achieved by physically partitioning the text data and text indexes (using local partitioned indexes), and ensuring that partitions are handled by separate Oracle RAC nodes. This way, you avoid duplication of the cache contents across multiple nodes and, therefore, maximize the benefit of Oracle RAC cache fusion.

In Oracle 10g Release 1, each Oracle Text index partition must be forced into a separate database file when the index is created. This enables the use of the "re-mastering" feature in Oracle RAC to force database file affinity, in which each node concentrates on a particular database file and, therefore, a particular Oracle Text index partition.

In Oracle 10g Release 2 and forward, Oracle supports database object-level affinity, which makes it much easier to allocate index objects ($I and $R tables) to particular nodes.

While Oracle RAC offers solutions for improving query throughput and performance, is not a "magic bullet," and it will not necessarily enable you to continue to get the same performance improvements as you scale up the data volumes. You are more likely to see improvements by increasing the amounts of memory available to the SGA cache, or by partitioning your data in such a way that queries will normally not need to hit all of the partitions of a table in order to provide the required set of query results.

Tuning Queries with Blocking Operations

Issuing a query with more than one predicate can cause a blocking operation in the execution plan. For example, consider the following mixed query:

select docid from mytab where contains(text, 'oracle', 1) > 0
AND colA > 5
AND colB > 1
AND colC > 3;

Assume that all predicates are unselective and colA, colB, and colC have bitmap indexes. The cost-based optimizer in Oracle Database chooses the following execution plan:

TABLE ACCESS BY ROWIDS
BITMAP CONVERSION TO ROWIDS
BITMAP AND
BITMAP INDEX COLA_BMX
BITMAP INDEX COLB_BMX
BITMAP INDEX COLC_BMX
BITMAP CONVERSION FROM ROWIDS
SORT ORDER BY
DOMAIN INDEX MYINDEX

Because the BITMAP AND is a blocking operation, Oracle Text must temporarily save the rowid and score pairs returned from the Oracle Text domain index before running the BITMAP AND operation.

Oracle Text attempts to save these rowid and score pairs in memory. However, when the size of the result set containing these rowid and score pairs exceeds the SORT_AREA_SIZE initialization parameter, Oracle Text spills these results to temporary segments on disk.

Because saving results to disk causes extra overhead, you can improve performance by increasing the SORT_AREA_SIZE parameter using ALTER SESSION as follows:

alter session set SORT_AREA_SIZE = <new memory size in bytes>;

For example, to set the buffer to approximately 8 megabytes, enter:

alter session set SORT_AREA_SIZE = 8300000;

See Also:

Oracle Database Performance Tuning Guide and Oracle Database Reference for more information on SORT_AREA_SIZE

Frequently Asked Questions About Query Performance

This section answers some of the frequently asked questions about query performance.

- What is Query Performance?

- What is the fastest type of text query?

- Should I collect statistics on my tables?

- How does the size of my data affect queries?

- How does the format of my data affect queries?

- What is a functional versus an indexed lookup?

- What tables are involved in queries?

- Does sorting the results slow a text-only query?

- How do I make an ORDER BY score query faster?

- Which memory settings affect querying?

- Does out-of-line LOB storage of wide base table columns improve performance?

- How can I make a CONTAINS query on more than one column faster?

- Is it OK to have many expansions in a query?

- How can local partition indexes help?

- Should I query in parallel?

- Should I index themes?

- When should I use a CTXCAT index?

- When is a CTXCAT index NOT suitable?

- What optimizer hints are available_ and what do they do?

What is Query Performance?

Answer: There are generally two measures of query performance:

- Response time, the time to get an answer to an individual query, and

- Throughput, the number of queries that can be run in any time period; for example, queries each second.

These two are related, but are not the same. In a heavily loaded system, you normally want maximum throughput, whereas in a relatively lightly loaded system, you probably want minimum response time. Also, some applications require a query to deliver all its hits to the user, whereas others might only require the first 20 hits from an ordered set. It is important to distinguish between these two scenarios.

What is the fastest type of text query?

Answer: The fastest type of query will meet the following conditions:

- Single CONTAINS clause

- No other conditions in the WHERE clause

- No ORDER BY clause at all

- Only the first page of results is returned (for example, the first 10 or 20 hits).

Should I collect statistics on my tables?

Answer: Yes. Collecting statistics on your tables enables Oracle Text to do cost-based analysis. This helps Oracle Text choose the most efficient execution plan for your queries.

If your queries are always pure text queries (no structured predicate and no joins), you should delete statistics on your Oracle Text index.

How does the size of my data affect queries?

Answer: The speed at which the text index can deliver ROWIDs is not affected by the actual size of the data. Text query speed will be related to the number of rows that must be fetched from the index table, number of hits requested, number of hits produced by the query, and the presence or absence of sorting.

How does the format of my data affect queries?

Answer: The format of the documents (plain ASCII text, HTML or Microsoft Word) should make no difference to query speed. The documents are filtered to plain text at indexing time, not query time.

The cleanliness of the data will make a difference. Spell-checked and sub-edited text for publication tends to have a much smaller total vocabulary (and therefore size of the index table) than informal text such as e-mails, which will contain many spelling errors and abbreviations. For a given index memory setting, the extra text takes up more memory, which can lead to more fragmented rows than in the cleaner text, which can adversely affect query response time.

What is a functional versus an indexed lookup?

Answer: There are two ways the kernel can query the text index. In the first and most common case, the kernel asks the text index for all the rowids that satisfy a particular text search. These rowids are returned in batches. In the second, the kernel passes individual rowids to the text index, and asks whether that particular rowid satisfies a certain text criterion.

The second is known as a functional lookup, and is most commonly done where there is a very selective structured clause, so that only a few rowids must be checked against the text index. An example of a search where a functional lookup may be used:

SELECT ID, SCORE(1), TEXT FROM MYTABLE

WHERE START_DATE = '21 Oct 1992'         <- highly selective
AND CONTAINS (TEXT, 'commonword') > 0    <- unselective

Functional invocation is also used for text query ordered by structured column (for example date, price) and text query is unselective.

What tables are involved in queries?

Answer: All queries look at the index token table. Its name has the form DR$indexname$I. This contains the list of tokens (column TOKEN_TEXT) and the information about the row and word positions where the token occurs (column TOKEN_INFO).

The row information is stored as internal DOCID values. These must be translated into external ROWID values. The table used for this depends on the type of lookup: For functional lookups, the $K table, DR$indexname$K, is used. This is a simple Index Organized Table (IOT) which contains a row for each DOCID/ROWID pair.

For indexed lookups, the $R table, DR$indexname$R, is used. This holds the complete list of ROWIDs in a BLOB column.

Hence we can easily find out whether a functional or indexed lookup is being used by examining a SQL trace, and looking for the $K or $R tables.

Note:

These internal index tables are subject to change from release to release. Oracle recommends that you do not directly access these tables in your application.

Does sorting the results slow a text-only query?

Answer: Yes, it certainly does.

If there is no sorting, then Oracle Text can return results as it finds them, which is quicker in the common case where the application needs to display only a page of results at a time.

How do I make an ORDER BY score query faster?

Answer: Sorting by relevance (SCORE(n)) can be extremely quick if the FIRST_ROWS(n) hint is used. In this case, Oracle Text performs a high speed internal sort when fetching from the text index tables.

An example of such a query:

SELECT /*+ FIRST_ROWS(10) */ ID, SCORE(1), TEXT FROM mytable
WHERE CONTAINS (TEXT, 'searchterm', 1) > 0
ORDER BY SCORE(1) DESC;

Note that for this to work efficiently, there must be no other criteria in the WHERE clause other than a single CONTAINS.

Which memory settings affect querying?

Answer: For querying, you want to strive for a large system global area (SGA). You can set these parameters related to SGA in your Oracle Database initialization file. You can also set these parameters dynamically.

The SORT_AREA_SIZE parameter controls the memory available for sorting for ORDER BY queries. You should increase the size of this parameter if you frequently order by structured columns.

See Also:

- Oracle Database Administrator's Guide for more information on setting SGA related parameters

- Oracle Database Performance Tuning Guide for more information on memory allocation and setting the SORT_AREA_SIZE parameter

Does out-of-line LOB storage of wide base table columns improve performance?

Answer: Yes. Typically, a SELECT statement selects more than one column from your base table. Because Oracle Text fetches columns to memory, it is more efficient to store wide base table columns such as LOBs out of line, especially when these columns are rarely updated but frequently selected.

When LOBs are stored out of line, only the LOB locators need to be fetched to memory during querying. Out of line storage reduces the effective size of the base table making it easier for Oracle Text to cache the entire table to memory. This reduces the cost of selecting columns from the base table, and hence speeds up text queries.

In addition, having smaller base tables cached in memory enables more index table data to be cached during querying, which improves performance.

How can I make a CONTAINS query on more than one column faster?

Answer: The fastest type of query is one where there is only a single CONTAINS clause, and no other conditions in the WHERE clause.

Consider the following multiple CONTAINS query:

SELECT title, isbn FROM booklist
WHERE CONTAINS (title, 'horse') > 0
AND CONTAINS (abstract, 'racing') > 0

We can obtain the same result with section searching and the WITHIN operator as follows:

SELECT title, isbn FROM booklist
WHERE CONTAINS (alltext,
'horse WITHIN title AND racing WITHIN abstract')>0

This query completes more quickly. To use a query like this, we must copy all the data into a single text column for indexing, with section tags around each column's data. This can be done with PL/SQL procedures before indexing, or by making use of the USER_DATASTORE datastore during indexing to synthesize structured columns with the text column into one document.

Is it OK to have many expansions in a query?

Answer: Each distinct word used in a query requires at least one row to be fetched from the index table. It is therefore best to keep the number of expansions down as much as possible.

You should not use expansions such as wild cards, thesaurus, stemming and fuzzy matching unless they are necessary to the task. In general, a few expansions (for example, 10 to 20) does not cause difficulty, but avoid having large numbers of explansions (80 or 100) in a query. The query feedback mechanism can be used to determine the number of expansions for any particular query expression.

In addition for wildcard and stem queries, you can remove the cost of term expansion from query time to index time by creating prefix, substring or stem indexes. Query performance increases at the cost of longer indexing time and added disk space.

Prefix and substring indexes can improve wildcard performance. You enable prefix and substring indexing with the BASIC_WORDLIST preference. The following example sets the wordlist preference for prefix and substring indexing. For prefix indexing, it specifies that Oracle Text create token prefixes between 3 and 4 characters long:

begin

ctx_ddl.create_preference('mywordlist', 'BASIC_WORDLIST');
ctx_ddl.set_attribute('mywordlist','PREFIX_INDEX','TRUE');
ctx_ddl.set_attribute('mywordlist','PREFIX_MIN_LENGTH', '3');
ctx_ddl.set_attribute('mywordlist','PREFIX_MAX_LENGTH', '4');
ctx_ddl.set_attribute('mywordlist','SUBSTRING_INDEX', 'YES');

end

You enable stem indexing with the BASIC_LEXER preference:

begin

ctx_ddl.create_preference('mylex', 'BASIC_LEXER');
ctx_ddl.set_attribute ( 'mylex', 'index_stems', 'ENGLISH');

end;

How can local partition indexes help?

Answer: You can create local partitioned CONTEXT indexes on partitioned tables. This means that on a partitioned table, each partition has its own set of index tables. Effectively, there are multiple indexes, but the results from each are combined as necessary to produce the final result set.

The index is created using the LOCAL keyword:

CREATE INDEX index_name ON table_name (column_name)
INDEXTYPE IS ctxsys.context
PARAMETERS ('...')
LOCAL

With partitioned tables and local indexes, you can improve performance of the following types of CONTAINS queries:

- Range Search on Partition Key Column
This is a query that restricts the search to a particular range of values on a column that is also the partition key.

- ORDER BY Partition Key Column
This is a query that requires only the first n hits and the ORDER BY clause names the partition key

See Also:

"Improved Response Time using Local Partitioned CONTEXT Index"

Should I query in parallel?

Answer: It depends on system load and server capacity. Even though parallel querying is the default behavior for indexes created in parallel, it usually results in degrading overall query throughput on heavily loaded systems.

In general, parallel queries are particularly appropriate for DSS or analytical systems with large data collections, multiple CPUs, and low number of concurrent users.

See Also:

"Using Parallel Queries"

Should I index themes?

Answer: Indexing theme information with a CONTEXT index takes longer and also increases the size of your index. However, theme indexes enable ABOUT queries to be more precise by using the knowledge base. If your application uses ABOUT queries heavily, it might be worthwhile to create a theme component to the index, despite the extra indexing time and extra storage space required.

See Also:

"ABOUT Queries and Themes"

When should I use a CTXCAT index?

Answer: CTXCAT indexes work best when text is in small chunks, maybe a few lines maximum, and searches need to restrict or sort the result set according to certain structured criteria, usually numbers or dates.

For example, consider an on-line auction site. Each item for sale has a short description, a current bid price, and dates for the start and end of the auction. A user might want to see all the records with antique cabinet in the description, with a current bid price less than $500. Because he is particularly interested in newly posted items, he wants the results sorted by auction start time.

Such a search is not always efficient with a CONTAINS structured query on a CONTEXT index, where the response time can vary significantly depending on the structured and CONTAINS clauses. This is because the intersection of structured and CONTAINS clauses or the ordering of text query is computed during query time.

By including structured information such as price and date within the CTXCAT index, query response time is always in an optimal range regardless of search criteria. This is because the interaction between text and structured query is pre-computed during indexing. Consequently query response time is optimum.

When is a CTXCAT index NOT suitable?

Answer: There are differences in the time and space needed to create the index. CTXCAT indexes take a bit longer to create and use considerably more disk space than CONTEXT indexes. If you are tight on disk space, you should consider carefully whether CTXCAT indexes are appropriate for you.

With respect to query operators, you can now use the richer CONTEXT grammar in CATSEARCH queries with query templates. The older restriction of a single CATSEARCH query grammar no longer holds.

What optimizer hints are available, and what do they do?

Answer: The optimizer hint INDEX(table column) can be used in the usual way to drive the query with a text or b-tree index.

You can also use the NO_INDEX(table column) hint to disable a specific index.

Additionally, the FIRST_ROWS(n) hint has a special meaning for text queries and should be used when you need the first n hits to a query. Use of the DOMAIN_INDEX_SORT hint in conjunction with ORDER BY SCORE(n) DESC tells the Oracle optimizer to accept a sorted set from the text index, and not to do a further sort.

See Also:

"Optimizing Queries for Response Time"

Frequently Asked Questions About Indexing Performance

This section answers some of the frequently asked questions about indexing performance.

- How long should indexing take?

- Which index memory settings should I use?

- How much disk overhead will indexing require?

- How does the format of my data affect indexing?

- Can parallel indexing improve performance?

- How can I improve index performance for creating local partitioned index?

- How can I tell how much indexing has completed?

How long should indexing take?

Answer: Indexing text is a resource-intensive process. The speed of indexing will depend on the power of the hardware involved. Indexing speed depends on CPU and I/O capacity. Given sufficient I/O capacity to read in the original data and write out index entries, then CPU will be the limiting factor.

Tests with Intel x86 (Core 2 architecture, 2.5GHz) CPUs have shown that Oracle Text can index around 100GB of text per CPU core, per day. This would be expected to increase as CPU clock speeds increase and/or CPU architectures become more efficient.

Other factors such as your document format, location of your data, and the calls to user-defined datastores, filters, and lexers can have an impact on your indexing speed.

Which index memory settings should I use?

Answer: You can set your index memory with the system parameters DEFAULT_INDEX_MEMORY and MAX_INDEX_MEMORY. You can also set your index memory at run time with the CREATE INDEX memory parameter in the parameter string.

You should aim to set the DEFAULT_INDEX_MEMORY value as high as possible, without causing paging.

You can also improve Indexing performance by increasing the SORT_AREA_SIZE system parameter.

Oracle recommends that you use a large index memory setting. Large settings, even up to hundreds of megabytes, can improve the speed of indexing, and reduce the fragmentation of the final indexes. However, if you set the index memory setting too high, then memory paging can occur that will reduce indexing speed.

With parallel indexing, each stream requires its own index memory. When dealing with very large tables, you can tune your database system global area (SGA) differently for indexing and retrieval. For querying, you want to get as much information cached in the system global area's (SGA) block buffer cache as possible. So you should allocate a large amount of memory to the block buffer cache. But this will not make any difference to indexing, so you would be better off reducing the size of the SGA to make more room for a large index memory settings during indexing.

You set the size of SGA in your Oracle Database initialization file.

See Also:

- Oracle Text Reference to learn more about Oracle Text system parameters

- Oracle Database Administrator's Guide for more information on setting SGA related parameters

- Oracle Database Performance Tuning Guide for more information on memory allocation and setting the SORT_AREA_SIZE parameter

How much disk overhead will indexing require?

Answer: The overhead, the amount of space needed for the index tables, varies between about 50% of the original text volume and 200%. Generally, the larger the total amount of text, the smaller the overhead, but many small records will use more overhead than fewer large records. Also, clean data (such as published text) will require less overhead than dirty data such as e-mails or discussion notes, because the dirty data is likely to include many unique words from mis-spellings and abbreviations.

A text-only index is smaller than a combined text and theme index. A prefix and substring index makes the index significantly larger.

How does the format of my data affect indexing?

Answer: You can expect much lower storage overhead for formatted documents such as Microsoft Word files because such documents tend to be very large compared to the actual text held in them. So 1GB of Word documents might only require 50MB of index space, whereas 1GB of plain text might require 500MB, because there is ten times as much plain text in the latter set.

Indexing time is less clear-cut. Although the reduction in the amount of text to be indexed will have an obvious effect, you must balance this out against the cost of filtering the documents with the AUTO_FILTER filter or other user-defined filters.

Can parallel indexing improve performance?

Answer: Parallel indexing can improve index performance when you have a large amount of data, and have multiple CPUs.

You use the PARALLEL keyword when creating the index:

CREATE INDEX index_name ON table_name (column_name)
INDEXTYPE IS ctxsys.context PARAMETERS ('...') PARALLEL 3;

This will create the index with up to three separate indexing processes depending on your resources.

Parallel indexing can also be used to create local partitioned indexes on partitioned tables. However, indexing performance only improves when you have multiple CPUs.

Note:

Using PARALLEL to create a local partitioned index enables parallel queries. (Creating a non-partitioned index in parallel does not turn on parallel query processing.)

Parallel querying degrades query throughput especially on heavily loaded systems. Because of this, Oracle recommends that you disable parallel querying after parallel indexing. To do so, use ALTER INDEX NOPARALLEL.

How can I improve index performance for creating local partitioned index?

Answer: When you have multiple CPUs, you can improve indexing performance by creating a local index in parallel. There are two ways to index in parallel:

You can create a local partitioned index in parallel in two ways:

- Use the PARALLEL clause with the LOCAL clause in CREATE INDEX.In this case, the maximum parallel degree is limited to the number of partitions you have.

- Create an unusable index first, then run the DBMS_PCLXUTIL.BUILD_PART_INDEX utility. This method can result in a higher degree of parallelism, especially if you have more CPUs than partitions.

The following is an example for the second method. In this example, the base table has three partitions. We create a local partitioned unusable index first, the run the DBMS_PCLUTIL.BUILD_PART_INDEX, which builds the 3 partitions in parallel (inter-partition parallelism). Also inside each partition, index creation is done in parallel (intra-partition parallelism) with a parallel degree of 2.

create index tdrbip02bx on tdrbip02b(text)
indextype is ctxsys.context local (partition tdrbip02bx1,
partition tdrbip02bx2,
partition tdrbip02bx3)
unusable;

exec dbms_pclxutil.build_part_index(3,2,'TDRBIP02B','TDRBIP02BX',TRUE);

How can I tell how much indexing has completed?

Answer: You can use the CTX_OUTPUT.START_LOG procedure to log output from the indexing process. Filename will normally be written to $ORACLE_HOME/ctx/log, but you can change the directory using the LOG_DIRECTORY parameter in CTX_ADM.SET_PARAMETER.

See Also:

Oracle Text Reference to learn more about using this procedure

Frequently Asked Questions About Updating the Index

This section answers some of the frequently asked questions about updating your index and related performance issues.

- How often should I index new or updated records?

- How can I tell when my indexes are getting fragmented?

- Does memory allocation affect index synchronization?

How often should I index new or updated records?

Answer: The less often you run reindexing with CTX_DDL.SYNC_INDEX, the less fragmented your indexes will be, and the less you will need to optimize them.

However, this means that your data will become progressively more out of date, which may be unacceptable for your users.

Overnight indexing is acceptable for many systems. In this case, data that is less than a day old is not searchable. Other systems use hourly, ten minute, or five minute updates.

See Also:

- Oracle Text Reference to learn more about using CTX_DDL.SYNC_INDEX

- "Managing DML Operations for a CONTEXT Index"

How can I tell when my indexes are getting fragmented?

Answer: The best way is to time some queries, run index optimization, then time the same queries (restarting the database to clear the SGA each time, of course). If the queries speed up significantly, then optimization was worthwhile. If they don't, you can wait longer next time.

You can also use CTX_REPORT.INDEX_STATS to analyze index fragmentation.

See Also:

- Oracle Text Reference to learn more about using the CTX_REPORT package

- "Optimizing the Index"

Does memory allocation affect index synchronization?

Answer: Yes, the same way as for normal indexing. There are often far fewer records to be indexed during a synchronize operation, so it is not usually necessary to provide hundreds of megabytes of indexing memory.

8 Searching Document Sections in Oracle Text

This chapter describes how to use document sections in an Oracle Text query application.

The following topics are discussed in this chapter:

- About Oracle Text Document Section Searching

- HTML Section Searching with Oracle Text

- XML Section Searching with Oracle Text

About Oracle Text Document Section Searching

Section searching enables you to narrow text queries down to blocks of text within documents. Section searching is useful when your documents have internal structure, such as HTML and XML documents.

You can also search for text at the sentence and paragraph level.

This section contains these topics:

- Enabling Oracle Text Section Searching

- Oracle Text Section Types

- Oracle Text Section Attributes

Enabling Oracle Text Section Searching

The steps for enabling section searching for your document collection are:

1. Create a Section Group

2. Define Your Sections

3. Index Your Documents

4. Section Searching with the WITHIN Operator

5. Path Searching with INPATH and HASPATH Operators

Create a Section Group

Section searching is enabled by defining section groups. You use one of the system-defined section groups to create an instance of a section group. Choose a section group appropriate for your document collection.

You use section groups to specify the type of document set you have and implicitly indicate the tag structure. For instance, to index HTML tagged documents, you use the HTML_SECTION_GROUP. Likewise, to index XML tagged documents, you can use the XML_SECTION_GROUP.

Table 8-1 lists the different types of section groups you can use:

Table 8-1 Types of Section Groups

Section Group Preference

Description

NULL_SECTION_GROUP

This is the default. Use this group type when you define no sections or when you define only SENTENCE or PARAGRAPH sections.

BASIC_SECTION_GROUP

Use this group type for defining sections where the start and end tags are of the form <A> and </A>.

Note: This group type dopes not support input such as unbalanced parentheses, comments tags, and attributes. Use HTML_SECTION_GROUP for this type of input.

HTML_SECTION_GROUP

Use this group type for indexing HTML documents and for defining sections in HTML documents.

XML_SECTION_GROUP

Use this group type for indexing XML documents and for defining sections in XML documents.

AUTO_SECTION_GROUP

Use this group type to automatically create a zone section for each start-tag/end-tag pair in an XML document. The section names derived from XML tags are case-sensitive as in XML.

Attribute sections are created automatically for XML tags that have attributes. Attribute sections are named in the form tag@attribute.

Stop sections, empty tags, processing instructions, and comments are not indexed.

The following limitations apply to automatic section groups:

- You cannot add zone, field or special sections to an automatic section group.

- Automatic sectioning does not index XML document types (root elements.) However, you can define stop-sections with document type.

- The length of the indexed tags including prefix and namespace cannot exceed 64 bytes. Tags longer than this are not indexed.

PATH_SECTION_GROUP

Use this group type to index XML documents. Behaves like the AUTO_SECTION_GROUP.

The difference is that with this section group you can do path searching with the INPATH and HASPATH operators. Queries are also case-sensitive for tag and attribute names.

NEWS_SECTION_GROUP

Use this group for defining sections in newsgroup formatted documents according to RFC 1036.

Note:

Documents sent to the HTML, XML, AUTO and PATH sectioners must begin with \s*<, where \s* represents zero or more whitespace characters. Otherwise, the document is treated as a plaintext document, and no sections are recognized.

You use the CTX_DDL package to create section groups and define sections as part of section groups. For example, to index HTML documents, create a section group with HTML_SECTION_GROUP:

begin
ctx_ddl.create_section_group('htmgroup', 'HTML_SECTION_GROUP');
end;

Define Your Sections

You define sections as part of the section group. The following example defines a zone section called heading for all text within the HTML < H1> tag:

begin
ctx_ddl.create_section_group('htmgroup', 'HTML_SECTION_GROUP');
ctx_ddl.add_zone_section('htmgroup', 'heading', 'H1');
end;

Note:

If you are using the AUTO_SECTION_GROUP or PATH_SECTION_GROUP to index an XML document collection, then you need not explicitly define sections. The system does this for you during indexing.

See Also:

- "Oracle Text Section Types" for more information about sections

- "XML Section Searching with Oracle Text" for more information about section searching with XML

Index Your Documents

When you index your documents, you specify your section group in the parameter clause of CREATE INDEX.

create index myindex on docs(htmlfile) indextype is ctxsys.context
parameters('filter ctxsys.null_filter section group htmgroup');

Section Searching with the WITHIN Operator

When your documents are indexed, you can query within sections using the WITHIN operator. For example, to find all the documents that contain the word Oracle within their headings, enter the following query:

'Oracle WITHIN heading'

See Also:

Oracle Text Reference to learn more about using the WITHIN operator

Path Searching with INPATH and HASPATH Operators

When you use the PATH_SECTION_GROUP, the system automatically creates XML sections for you. In addition to using the WITHIN operator to enter queries, you can enter path queries with the INPATH and HASPATH operators.

See Also:

- "XML Section Searching with Oracle Text" to learn more about using these operators

- Oracle Text Reference to learn more about using the INPATH operator

Oracle Text Section Types

All section types are blocks of text in a document. However, sections can differ in the way that they are delimited and the way that they are recorded in the index. Sections can be one of the following types:

- Zone Section

- Field Section

- Stop Section

- MDATA Section

- NDATA Section

- SDATA Section

- Attribute Section (for XML documents)

- Special Sections (sentence or paragraphs)

Table 8-2 shows which section types may be used with each kind of section group.

Table 8-2 Section Types and Section Groups

Section Group

ZONE

FIELD

STOP

MDATA

NDATA

SDATA

ATTRIBUTE

SPECIAL

NULL

NO

NO

NO

NO

NO

NO

NO

YES

BASIC

YES

YES

NO

YES

YES

YES

NO

YES

HTML

YES

YES

NO

YES

YES

YES

NO

YES

XML

YES

YES

NO

YES

YES

YES

YES

YES

NEWS

YES

YES

NO

YES

YES

YES

NO

YES

AUTO

NO

NO

YES

NO

NO

NO

NO

NO

PATH

NO

NO

NO

NO

NO

NO

NO

NO

Zone Section

A zone section is a body of text delimited by start and end tags in a document. The positions of the start and end tags are recorded in the index so that any words in between the tags are considered to be within the section. Any instance of a zone section must have a start and an end tag.

For example, the text between the <TITLE> and </TITLE> tags can be defined as a zone section as follows:

<TITLE>Tale of Two Cities</TITLE>
It was the best of times...

Zone sections can nest, overlap, and repeat within a document.

When querying zone sections, you use the WITHIN operator to search for a term across all sections. Oracle Text returns those documents that contain the term within the defined section.

Zone sections are well suited for defining sections in HTML and XML documents. To define a zone section, use CTX_DDL.ADD_ZONE_SECTION.

For example, assume you define the section booktitle as follows:

begin
ctx_ddl.create_section_group('htmgroup', 'HTML_SECTION_GROUP');
ctx_ddl.add_zone_section('htmgroup', 'booktitle', 'TITLE');
end;

After you index, you can search for all the documents that contain the term Cities within the section booktitle as follows:

'Cities WITHIN booktitle'

With multiple query terms such as (dog and cat) WITHIN booktitle, Oracle Text returns those documents that contain cat and dog within the same instance of a booktitle section.

Repeated Zone Sections

Zone sections can repeat. Each occurrence is treated as a separate section. For example, if <H1> denotes a heading section, they can repeat in the same documents as follows:

<H1> The Brown Fox </H1>
<H1> The Gray Wolf </H1>

Assuming that these zone sections are named Heading, the query Brown WITHIN Heading returns this document. However, a query of (Brown and Gray) WITHIN Heading does not.

Overlapping Zone Sections

Zone sections can overlap each other. For example, if <B> and <I> denote two different zone sections, they can overlap in a document as follows:

plain <B> bold <I> bold and italic </B> only italic </I>  plain

Nested Zone Sections

Zone sections can nest, including themselves as follows:

<TD> <TABLE><TD>nested cell</TD></TABLE></TD>

Using the WITHIN operator, you can write queries to search for text in sections within sections. For example, assume the BOOK1, BOOK2, and AUTHOR zone sections occur as follows in documents doc1 and doc2:

doc1:

<book1> <author>Scott Tiger</author> This is a cool book to read.</book1>

doc2:

<book2> <author>Scott Tiger</author> This is a great book to read.</book2>

Consider the nested query:

'(Scott within author) within book1'

This query returns only doc1.

Field Section

A field section is similar to a zone section in that it is a region of text delimited by start and end tags. Field sections are more efficient than zone sections and are different than zone sections in that the region is indexed separately from the rest of the document. You can create an unlimited number of field sections.

Since field sections are indexed differently, you can also get better query performance over zone sections for when you have a large number of documents indexed.

Field sections are more suited to when you have a single occurrence of a section in a a document such as a field in a news header. Field sections can also be made visible to the rest of the document.

Unlike zone sections, field sections have the following restrictions:

- Field sections cannot overlap

- Field sections cannot repeat

- Field sections cannot nest

This section contains the following topics.

- Visible and Invisible Field Sections

- Nested Field Sections

- Repeated Field Sections

Visible and Invisible Field Sections

By default, field sections are indexed as a sub-document separate from the rest of the document. As such, field sections are invisible to the surrounding text and can only be queried by explicitly naming the section in the WITHIN clause.

You can make field sections visible if you want the text within the field section to be indexed as part of the enclosing document. Text within a visible field section can be queried with or without the WITHIN operator.

The following example shows the difference between using invisible and visible field sections.

The following code defines a section group basicgroup of the BASIC_SECTION_GROUP type. It then creates a field section in basicgroup called Author for the <A> tag. It also sets the visible flag to FALSE to create an invisible section:

begin
ctx_ddl.create_section_group('basicgroup', 'BASIC_SECTION_GROUP');
ctx_ddl.add_field_section('basicgroup', 'Author', 'A', FALSE);
end;

Because the Author field section is not visible, to find text within the Author section, you must use the WITHIN operator as follows:

'(Martin Luther King) WITHIN Author'

A query of Martin Luther King without the WITHIN operator does not return instances of this term in field sections. If you want to query text within field sections without specifying WITHIN, you must set the visible flag to TRUE when you create the section as follows:

begin
ctx_ddl.add_field_section('basicgroup', 'Author', 'A', TRUE);
end;

Nested Field Sections

Field sections cannot be nested. For example, if you define a field section to start with <TITLE> and define another field section to start with <FOO>, the two sections cannot be nested as follows:

<TITLE> dog <FOO> cat </FOO> </TITLE>

To work with nested sections, define them as zone sections.

Repeated Field Sections

Repeated field sections are allowed, but WITHIN queries treat them as a single section. The following is an example of repeated field section in a document:

<TITLE> cat </TITLE>
<TITLE> dog </TITLE>

The query dog and cat within title returns the document, even though these words occur in different sections.

To have WITHIN queries distinguish repeated sections, define them as zone sections.

Stop Section

A stop section may be added to an automatic section group. Adding a stop section causes the automatic section indexing operation to ignore the specified section in XML documents.

Note:

Adding a stop section causes no section information to be created in the index. However, the text within a stop section is always searchable.

Adding a stop section is useful when your documents contain many low-information tags. Adding stop sections also improves indexing performance with the automatic section group.

The number of stop sections you can add is unlimited.

Stop sections do not have section names and hence are not recorded in the section views.

MDATA Section

An MDATA section is used to reference user-defined metadata for a document. Using MDATA sections can speed up mixed queries. There is no limit to the number of MDATA sections that can be returned in a query.

Consider the case in which you want to query both according to text content and document type (magazine or newspaper or novel). You could create an index with a column for text and a column for the document type, and then perform a mixed query of this form—in this case, searching for all novels with the phrase Adam Thorpe (author of the novel Ulverton):

SELECT id FROM documents
WHERE doctype = 'novel'
AND CONTAINS(text, 'Adam Thorpe')>0;

However, it is usually faster to incorporate the attribute (in this case, the document type) into a field section, rather than use a separate column, and then use a single CONTAINS query:

SELECT id FROM documents
WHERE CONTAINS(text, 'Adam Thorpe AND novel WITHIN doctype')>0;

There are two drawbacks to this approach:

- Each time the attribute is updated, the entire text document must be re-indexed, resulting in increased index fragmentation and slower rates of processing DML.

- Field sections tokenize the section value. This has several effects. Special characters in metadata, such as decimal points or currency characters, are not easily searchable; value searching (searching for Thurston Howell but not Thurston Howell, Jr.) is difficult; multi-word values are queried by phrase, which is slower than single-token searching; and multi-word values do not show up in browse-words, making author browsing or subject browsing impossible.

For these reasons, using MDATA sections instead of field sections may be worthwhile. MDATA sections are indexed like field sections, but metadata values can be added to and removed from documents without the need to re-index the document text. Unlike field sections, MDATA values are not tokenized. Additionally, MDATA section indexing generally takes up less disk space than field section indexing.

Use CTX_DDL.ADD_MDATA_SECTION to add an MDATA section to a section group. This example adds an MDATA section called AUTHOR and gives it the value Soseki Natsume (author of the novel Kokoro).

ctx_ddl.create.section.group('htmgroup', 'HTML_SECTION_GROUP');
ctx_ddl.add_mdata_section('htmgroup', 'author', 'Soseki Natsume');

MDATA values can be changed with CTX_DDL.ADD_MDATA and removed with CTX_DDL.REMOVE_MDATA. Also, MDATA sections can have multiple values. Only the owner of the index is allowed to call CTX_DDL.ADD_MDATA and CTX_DDL.REMOVE_MDATA.

Neither CTX_DDL.ADD_MDATA nor CTX_DDL.REMOVE_MDATA are supported for CTXCAT and CTXRULE indexes.

MDATA values are not passed through a lexer. Instead, all values undergo a simplified normalization as follows:

- Leading and trailing whitespace on the value is removed.

- The value is truncated to 64 bytes.

- The value is indexed as a single value; if the value consists of multiple words, it is not broken up.

- Case is preserved. If the document is dynamically generated, you can implement case-insensitivity by uppercasing MDATA values and making sure to search only in uppercase.

After a document has had MDATA metadata added to it, you can query for that metadata using the MDATA CONTAINS query operator:

SELECT id FROM documents
WHERE CONTAINS(text, 'Tokyo and MDATA(author, Soseki Natsume)')>0;

This query will only be successful if an AUTHOR tag has the exact value Soseki Natsume (after simplified tokenization). Soseki or Natsume Soseki will not work.

Other things to note about MDATA:

- MDATA values are not highlightable, will not appear in the output of CTX_DOC.TOKENS, and will not show up when FILTER PLAINTEXT is enabled.

- MDATA sections must be unique within section groups. You cannot have an MDATA section named FOO and a zone or field section of the same name in the same section group.

- Like field sections, MDATA sections cannot overlap or nest. An MDATA section is implicitly closed by the first tag encountered. For instance, in this example:

<AUTHOR>Dickens <B>Shelley</B> Keats</AUTHOR>

The <B> tag closes the AUTHOR MDATA section; as a result, this document has an AUTHOR of 'Dickens', but not of 'Shelley' or 'Keats'.

- To prevent race conditions, each call to ADD_MDATA and REMOVE_MDATA locks out other calls on that rowid for that index for all values and sections. However, since ADD_MDATA and REMOVE_MDATA do not commit, it is possible for an application to deadlock when calling them both. It is the application's responsibility to prevent deadlocking.

See Also:

- The CONTAINS query operators chapter of the Oracle Text Reference for information on the MDATA operator

- The CTX_DDL package chapter of Oracle Text Reference for information on adding and removing MDATA sections

NDATA Section

Fields containing data to be indexed for name searching can be specified exclusively by adding NDATA sections to section groups of type: BASIC_SECTION_GROUP, HTML_SECTION_GROUP, or XML_SECTION_GROUP.

Users can synthesize textual documents, which contain name data, using two possible datastores: MULTI_COLUMN_DATASTORE or USER_DATASTORE. The following example uses MULTI_COLUMN_DATASTORE to pick up relevant columns containing the name data for indexing:

create table people(firstname varchar2(80), surname varchar2(80));
insert into people values('John', 'Smith');
commit;
begin
ctx_ddl.create_preference('nameds', 'MULTI_COLUMN_DATASTORE');
ctx_ddl.set_attribute('nameds', 'columns', 'firstname,surname');
end;
/

This produces the following virtual text for indexing:

<FIRSTNAME>
John
</FIRSTNAME>
<SURNAME>
Smith
</SURNAME>

You can then create NDATA sections for FIRSTNAME and SURNAME sections:

begin
ctx_ddl.create_section_group('namegroup', 'BASIC_SECTION_GROUP');
ctx_ddl.add_ndata_section('namegroup', 'FIRSTNAME', 'FIRSTNAME');
ctx_ddl.add_ndata_section('namegroup', 'SURNAME', 'SURNAME');
end;
/

Then create the index using the datastore preference and section group preference created earlier:

create index peopleidx on people(firstname) indextype is ctxsys.context
parameters('section group namegroup datastore nameds');

NDATA sections support both single- and multi-byte data, however, there are character- and term-based limitations. NDATA section data that is indexed is constrained as follows:

- the number of characters in a single, white space delimited term
511

- the number of white space delimited terms
255

- the total number of characters, including white spaces
511

SDATA Section

The value of an SDATA section is extracted from the document text like other sections, but is indexed as structured data, also referred to as SDATA. Using SDATA sections supports operations such as projection, range searches, and ordering. It also enables SDATA indexing of section data such as embedded tags, and detail table or function invocations. This enables you to perform various combinations of text and structured searches in one single SQL statement.

SDATA operators should be used only as descendants of AND operators that also have non-SDATA children. SDATA operators are meant to be used as secondary, checking or non-driving, criteria. For instance, "find documents with DOG that also have price > 5", rather than "find documents with rating > 4".

Use CTX_DDL.ADD_SDATA_SECTION to add an SDATA section to a section group. Use CTX_DDL.UPDATE_SDATA to update the values of an existing SDATA section. When querying within an SDATA section, you must use the CONTAINS operator. The following example creates a table called items, and adds an SDATA section called my_sec_group, and then queries SDATA in the section.

After you create an SDATA section, you can further modify the attributes of the SDATA section using CTX_DDL.SET_SECTION_ATTRIBUTE.

Create the table items:

CREATE TABLE items
(id  NUMBER PRIMARY KEY,
doc VARCHAR2(4000));

INSERT INTO items VALUES (1, '<description> Honda Pilot </description>
<category> Cars & Trucks </category>
<price> 27000 </price>');
INSERT INTO items VALUES (2, '<description> Toyota Sequoia </description>
<category> Cars & Trucks </category>
<price> 35000 </price>');
INSERT INTO items VALUES (3, '<description> Toyota Land Cruiser </description>
<category> Cars & Trucks </category>
<price> 45000 </price>');
INSERT INTO items VALUES (4, '<description> Palm Pilot </description>
<category> Electronics </category>
<price> 5 </price>');
INSERT INTO items VALUES (5, '<description> Toyota Land Cruiser Grill </description>
<category> Parts & Accessories </category>
<price> 100 </price>');
COMMIT;

Add SDATA section my_sec_group:

BEGIN
CTX_DDL.CREATE_SECTION_GROUP('my_sec_group', 'BASIC_SECTION_GROUP');
CTX_DDL.ADD_SDATA_SECTION('my_sec_group', 'category', 'category', 'VARCHAR2');
CTX_DDL.ADD_SDATA_SECTION('my_sec_group', 'price', 'price', 'NUMBER');
END;

Create the CONTEXT index:

CREATE INDEX items$doc
ON items(doc)
INDEXTYPE IS CTXSYS.CONTEXT
PARAMETERS('SECTION GROUP my_sec_group');

Run a query:

SELECT id, doc
FROM items
WHERE contains(doc, 'Toyota
AND SDATA(category = ''Cars & Trucks'')
AND SDATA(price <= 40000 )') > 0;

Return the results:

ID DOC
---- ----------------------------------------------------------------------
2 <description> Toyota Sequoia </description>
<category> Cars & Trucks </category>
<price> 35000 </price>

The following example updates the value of the SDATA section price for a document having the rowid of 1, to a new value of 30000.

BEGIN
SELECT ROWID INTO rowid_to_update FROM items WHERE id=1;

CTX_DDL.UPDATE_SDATA('items$doc',
'price',
SYS.ANYDATA.CONVERTVARCHAR2('30000'),
rowid_to_update);
END;

After executing the above query, the price of Honda Pilot is changed from 27000 to 30000.

Note:

You can also add an SDATA section to an existing index, without rebuilding the index, using the ADD SDATA SECTION parameter of the ALTER INDEX PARAMETERS statement. See "ALTER INDEX" section of the Oracle Text Reference for more information.

See Also:

- The "CONTAINS" query section of the Oracle Text Reference for information on the SDATA operator

- The "CTX_DDL" package section of the Oracle Text Reference for information on adding and updating the SDATA sections and changing their attributes using the ADD_SDATA_SECTION, SET_SECTION_ATTRIBUTE, and the UPDATE_SDATA procedures

Attribute Section

You can define attribute sections to query on XML attribute text. You can also have the system automatically define and index XML attributes for you.

See Also:

"XML Section Searching with Oracle Text"

Special Sections

Special sections are not recognized by tags. Currently the only special sections supported are sentence and paragraph. This enables you to search for combination of words within sentences or paragraphs.

The sentence and paragraph boundaries are determined by the lexer. For example, the BASIC_LEXER recognizes sentence and paragraph section boundaries as follows:

Table 8-3 Sentence and Paragraph Section Boundaries for BASIC_LEXER

Special Section

Boundary

SENTENCE

WORD/PUNCT/WHITESPACE

WORD/PUNCT/NEWLINE

PARAGRAPH

WORD/PUNCT/NEWLINE/WHITESPACE

WORD/PUNCT/NEWLINE/NEWLINE

If the lexer cannot recognize the boundaries, no sentence or paragraph sections are indexed.

To add a special section, use the CTX_DDL.ADD_SPECIAL_SECTION procedure. For example, the following code enables searching within sentences within HTML documents:

begin
ctx_ddl.create_section_group('htmgroup', 'HTML_SECTION_GROUP');
ctx_ddl.add_special_section('htmgroup', 'SENTENCE');
end;

You can also add zone sections to the group to enable zone searching in addition to sentence searching. The following example adds the zone section Headline to the section group htmgroup:

begin
ctx_ddl.create_section_group('htmgroup', 'HTML_SECTION_GROUP');
ctx_ddl.add_special_section('htmgroup', 'SENTENCE');
ctx_ddl.add_zone_section('htmgroup', 'Headline', 'H1');
end;

Oracle Text Section Attributes

Section attributes are the settings related to the Oracle Text sections of tokenized type, such as, Field, Zone, Hybrid, and SDATA. Section attributes improve the query performance due to the finer control at the section level, rather than at the document level or index level.

By using the section attributes, you can:

- specify lexer preferences on certain sections of a document. This is useful for part-name searches, where a certain section of a document containing a part-name needs to be lexed differently than the rest of the document. The lexer preference can also be used for handling multi-lingual documents, where there is a section to language mapping.

- specify a substring index only on certain sections of a document. This helps in reducing the index size.

- specify creating prefix tokens only on certain sections of a document. The prefix tokens are used to improve the performance of right-truncated queries, but can also cause the index size to grow rapidly. Specifying prefix indexing only on certain sections provides improved performance for the right-truncated queries on the specific sections, without rapidly growing the size of the index.

- specify stoplists for certain sections of a document.

- specify creating a new section type that combines the flexibility of Zone sections with the performance of Field sections. Currently, Zone sections have poor performance compared to Field sections. However, Field sections do not support nested section search.

Section attributes are set using the procedure CTX_DDL.SET_SECTION_ATTRIBUTE.

Table 8-4 lists the section attributes that you can use:

Table 8-4 Section Attributes

Section Attribute

Description

visible

You can use the visible attribute for all the section types that are tokenized, except the zone section type. Thus, the visible attribute can be used for Field, Hybrid, and SDATA section types.

Specify TRUE to make the text visible within a document. This makes the text within the field section to be indexed as part of the enclosing document.

Default is FALSE. This makes the text within the field section to be indexed separately from the rest of the document.

For the Field section type, the visible attribute overrides the value specified in the CTX_DDL.ADD_FIELD_SECTION procedure.

lexer

You can use the lexer attribute for all the section types that are tokenized, that is, Field, Zone, Hybrid, and SDATA sections.

Specify the lexer preference name to decide the tokenization of an SDATA section. Default is NULL and the lexer for the main document is used.

The lexer preference must be valid at the time of calling the set_section_attribute procedure. If you try to drop one of the preferences when a field section still exists that refers to a lexer preference, the drop_preference procedure will fail.

wordlist

You can use the wordlist attribute for all the section types that are tokenized, that is, Field, Zone, Hybrid, and SDATA sections.

Specify the wordlist preference name for a section to enable section specific prefix indexing and substring indexing. Default is NULL and the wordlist for the main document is used.

The wordlist preference must be valid at the time of calling the set_section_attribute procedure. If you try to drop one of the preferences when a field section still exists that refers to a wordlist preference, the drop_preference procedure will fail.

stoplist

You can use the stoplist attribute for all the section types that are tokenized, that is, Field, Zone, Hybrid, and SDATA sections.

Specify the stoplist preference name for enabling section specific stoplist. Default is NULL and the stoplist for the main document is used.

The stoplist preference must be valid at the time of calling the set_section_attribute procedure. If you try to drop one of the preferences when a field section still exists that refers to a stoplist preference, the drop_preference procedure will fail.

The following example enables the visible attribute of a Field section:

begin
ctx_ddl.create_section_group(‘fieldgroup', ‘BASIC_SECTION_GROUP');
ctx_ddl.add_field_section(‘fieldgroup', ‘author', ‘AUTHOR');
ctx_ddl.set_section_attribute(‘fieldgroup', ‘author', ‘visible', ‘true');
end;

See Also:

Oracle Text Reference for the syntax of CTX_DDL.SET_SECTION_ATTRIBUTE procedure.

HTML Section Searching with Oracle Text

HTML has internal structure in the form of tagged text which you can use for section searching. For example, you can define a section called headings for the <H1> tag. This enables you to search for terms only within these tags across your document set.

To query, you use the WITHIN operator. Oracle Text returns all documents that contain your query term within the headings section. Thus, if you wanted to find all documents that contain the word oracle within headings, enter the following query:

'oracle within headings'

This section contains these topics:

- Creating HTML Sections

- Searching HTML Meta Tags

Creating HTML Sections

The following code defines a section group called htmgroup of type HTML_SECTION_GROUP. It then creates a zone section in htmgroup called heading identified by the <H1> tag:

begin
ctx_ddl.create_section_group('htmgroup', 'HTML_SECTION_GROUP');
ctx_ddl.add_zone_section('htmgroup', 'heading', 'H1');
end;

You can then index your documents as follows:

create index myindex on docs(htmlfile) indextype is ctxsys.context
parameters('filter ctxsys.null_filter section group htmgroup');

After indexing with section group htmgroup, you can query within the heading section by issuing a query as follows:

'Oracle WITHIN heading'

Searching HTML Meta Tags

With HTML documents you can also create sections for NAME/CONTENT pairs in <META> tags. When you do so you can limit your searches to text within CONTENT.

Example: Creating Sections for <META>Tags

Consider an HTML document that has a META tag as follows:

<META NAME="author" CONTENT="ken">

To create a zone section that indexes all CONTENT attributes for the META tag whose NAME value is author:

begin
ctx_ddl.create_section_group('htmgroup', 'HTML_SECTION_GROUP');
ctx_ddl.add_zone_section('htmgroup', 'author', 'meta@author');
end

After indexing with section group htmgroup, you can query the document as follows:

'ken WITHIN author'

XML Section Searching with Oracle Text

Like HTML documents, XML documents have tagged text which you can use to define blocks of text for section searching. The contents of a section can be searched on with the WITHIN or INPATH operators.

The following sections describe the different types of XML searching:

- Automatic Sectioning

- Attribute Searching

- Creating Document Type Sensitive Sections

- Path Section Searching

Automatic Sectioning

You can set up your indexing operation to automatically create sections from XML documents using the section group AUTO_SECTION_GROUP. The system creates zone sections for XML tags. Attribute sections are created for the tags that have attributes and these sections named in the form tag@attribute.

For example, the following statement creates the index myindex on a column containing the XML files using the AUTO_SECTION_GROUP:

CREATE INDEX myindex
ON xmldocs(xmlfile)
INDEXTYPE IS ctxsys.context
PARAMETERS ('datastore ctxsys.default_datastore
filter ctxsys.null_filter
section group ctxsys.auto_section_group'
);

Attribute Searching

You can search XML attribute text in one of two ways:

- Creating Attribute Sections
Create attribute sections with CTX_DDL.ADD_ATTR_SECTION and then index with XML_SECTION_GROUP. If you use AUTO_SECTION_GROUP when you index, attribute sections are created automatically. You can query attribute sections with the WITHIN operator.

- Searching Attributes with the INPATH Operator
Index with the PATH_SECTION_GROUP and query attribute text with the INPATH operator.

Creating Attribute Sections

Consider an XML file that defines the BOOK tag with a TITLE attribute as follows:

<BOOK TITLE="Tale of Two Cities">
It was the best of times.
</BOOK>

To define the title attribute as an attribute section, create an XML_SECTION_GROUP and define the attribute section as follows:

begin
ctx_ddl.create_section_group('myxmlgroup', 'XML_SECTION_GROUP');
ctx_ddl.add_attr_section('myxmlgroup', 'booktitle', 'book@title');
end;

To index:

CREATE INDEX myindex
ON xmldocs(xmlfile)
INDEXTYPE IS ctxsys.context
PARAMETERS ('datastore ctxsys.default_datastore
filter ctxsys.null_filter
section group myxmlgroup'
);

You can query the XML attribute section booktitle as follows:

'Cities within booktitle'

Searching Attributes with the INPATH Operator

You can search attribute text with the INPATH operator. To do so, you must index your XML document set with the PATH_SECTION_GROUP.

See Also:

"Path Section Searching"

Creating Document Type Sensitive Sections

For an XML document set that contains the <book> tag declared for different document types, you may want to create a distinct book section for each document type. The following scenario shows how to create book sections for each document type to improve search capability.

Assume that mydocname1 is declared as an XML document type (root element) as follows:

<!DOCTYPE mydocname1 ... [...

Within mydocname1, the element <book> is declared. For this tag, you can create a section named mybooksec1 that is sensitive to the tag's document type as follows:

begin

ctx_ddl.create_section_group('myxmlgroup', 'XML_SECTION_GROUP');
ctx_ddl.add_zone_section('myxmlgroup', 'mybooksec1', 'mydocname1(book)');

end;

Assume that mydocname2 is declared as another XML document type (root element) as follows:

<!DOCTYPE mydocname2 ... [...

Within mydocname2, the element <book> is declared. For this tag, you can create a section named mybooksec2 that is sensitive to the tag's document type as follows:

begin

ctx_ddl.create_section_group('myxmlgroup', 'XML_SECTION_GROUP');
ctx_ddl.add_zone_section('myxmlgroup', 'mybooksec2', 'mydocname2(book)');

end;

To query within the section mybooksec1, use WITHIN as follows:

'oracle within mybooksec1'

Path Section Searching

XML documents can have parent-child tag structures such as:

<A> <B> <C> dog </C> </B> </A>

In this scenario, tag C is a child of tag B which is a child of tag A.

With Oracle Text, you can do path searching with PATH_SECTION_GROUP. This section group enables you to specify direct parentage in queries, such as to find all documents that contain the term dog in element C which is a child of element B and so on.

With PATH_SECTION_GROUP, you can also perform attribute value searching and attribute equality testing.

The new operators associated with this feature are

- INPATH

- HASPATH

This section contains the following topics.

- Creating an Index with PATH_SECTION_GROUP

- Top-Level Tag Searching

- Any-Level Tag Searching

- Direct Parentage Searching

- Tag Value Testing

- Attribute Searching

- Attribute Value Testing

- Path Testing

- Section Equality Testing with HASPATH

Creating an Index with PATH_SECTION_GROUP

To enable path section searching, index your XML document set with PATH_SECTION_GROUP. For example:

Create the preference.

begin
ctx_ddl.create_section_group('xmlpathgroup', 'PATH_SECTION_GROUP');
end;

Create the index.

CREATE INDEX myindex
ON xmldocs(xmlfile)
INDEXTYPE IS ctxsys.context
PARAMETERS ('datastore ctxsys.default_datastore
filter ctxsys.null_filter
section group xmlpathgroup'
);

When you create the index, you can use the INPATH and HASPATH operators.

Top-Level Tag Searching

To find all documents that contain the term dog in the top-level tag <A>:

dog INPATH (/A)

or

dog INPATH(A)

Any-Level Tag Searching

To find all documents that contain the term dog in the <A> tag at any level:

dog INPATH(//A)

This query finds the following documents:

<A>dog</A>

and

<C><B><A>dog</A></B></C>

Direct Parentage Searching

To find all documents that contain the term dog in a B element that is a direct child of a top-level A element:

dog INPATH(A/B)

This query finds the following XML document:

<A><B>My dog is friendly.</B></A>

but does not find:

<C><B>My dog is friendly.</B></C>

Tag Value Testing

You can test the value of tags. For example, the query:

dog INPATH(A[B="dog"])

Finds the following document:

<A><B>dog</B></A>

But does not find:

<A><B>My dog is friendly.</B></A>

Attribute Searching

You can search the content of attributes. For example, the query:

dog INPATH(//A/@B)

Finds the document

<C><A  B="snoop dog"> </A> </C>

Attribute Value Testing

You can test the value of attributes. For example, the query

California INPATH (//A[@B = "home address"])

Finds the document:

<A B="home address">San Francisco, California, USA</A>

But does not find:

<A B="work address">San Francisco, California, USA</A>

Path Testing

You can test if a path exists with the HASPATH operator. For example, the query:

HASPATH(A/B/C)

finds and returns a score of 100 for the document

<A><B><C>dog</C></B></A>

without the query having to reference dog at all.

Section Equality Testing with HASPATH

You can use the HASPATH operator to do section quality tests. For example, consider the following query:

dog INPATH A

finds

<A>dog</A>

but it also finds

<A>dog park</A>

To limit the query to the term dog and nothing else, you can use a section equality test with the HASPATH operator. For example,

HASPATH(A="dog")

finds and returns a score of 100 only for the first document, and not the second.

See Also:

Oracle Text Reference to learn more about using the INPATH and HASPATH operators

9 Using Oracle Text Name Search

This chapter describes how to use the name search facility, and includes:

- Overview of Name Search

- Examples of Using Name Search

Overview of Name Search

Someone accustomed to the spelling rules of one culture can have difficulty applying those same rules to a name originating from a different culture. Name searching (also called name matching) provides a solution to match proper names that might differ in spelling due to orthographic variation. It also enables you to search for somewhat inaccurate data, such as might occur when a record's first name and surname are not properly segmented. This ability to handle somewhat inaccurate data is the main advantage of name searching.

Examples of Using Name Search

The following example illustrates how to use NDATA sections to search on names:

drop table people;

create table people (
full_name varchar2(2000)
);

insert into people values
('John Black Smith');

-- multi_column datastore is a convenient way of adding section tags around our data
exec ctx_ddl.drop_preference('name_ds')
begin
ctx_ddl.create_preference('name_ds', 'MULTI_COLUMN_DATASTORE');
ctx_ddl.set_attribute('name_ds', 'COLUMNS', 'full_name');
end;
/

exec ctx_ddl.drop_section_group('name_sg');
begin
ctx_ddl.create_section_group('name_sg', 'BASIC_SECTION_GROUP');
ctx_ddl.add_ndata_section('name_sg', 'full_name', 'full_name');
end;
/
-- You can optionally load a thesaurus of nicknames
-- HOST ctxload -thes -name nicknames -file nicknames.txt

exec ctx_ddl.drop_preference('name_wl');
begin
ctx_ddl.create_preference('name_wl', 'BASIC_WORDLIST');
ctx_ddl.set_attribute('name_wl', 'NDATA_ALTERNATE_SPELLING', 'FALSE');
ctx_ddl.set_attribute('name_wl', 'NDATA_BASE_LETTER', 'TRUE');
-- Include the following line only if you have loaded the thesaurus
-- file nicknames.txt:
-- ctx_ddl.set_attribute('name_wl', 'NDATA_THESAURUS', 'nicknames');
ctx_ddl.set_attribute('name_wl', 'NDATA_JOIN_PARTICLES',
'de:di:la:da:el:del:qi:abd:los:la:dos:do:an:li:yi:yu:van:jon:un:sai:ben:al');
end;
/

create index people_idx on people(full_name) indextype is ctxsys.context
parameters ('datastore name_ds section group name_sg wordlist name_wl');

-- Now you can do name searches with the following SQL:

var name varchar2(80);
exec :name := 'Jon Blacksmith'

select /*+ FIRST_ROWS */ full_name, score(1)
from people
where contains(full_name,  'ndata( full_name, '||:name||') ',1)>0
order by score(1) desc
/

The following example illustrates a more complicated version of using NDATA sections to search on names:

create table emp (
first_name    varchar2(30),
middle_name   varchar2(30),
last_name     varchar2(30),
email         varchar2(30),
phone         varchar2(30));

insert into emp values
('John', 'Black', 'Smith', 'john.smith@example.org', '123-456-7890');

-- user datastore procedure
create or replace procedure empuds_proc
(rid in rowid, tlob in out nocopy clob) is
tag varchar2(30);
phone varchar2(30);
begin
for c1 in (select FIRST_NAME, MIDDLE_NAME, LAST_NAME, EMAIL, PHONE
from emp
where rowid = rid)
loop
tag :='<email>';
dbms_lob.writeappend(tlob, length(tag), tag);
if (c1.EMAIL is not null) then
dbms_lob.writeappend(tlob, length(c1.EMAIL), c1.EMAIL);
end if;
tag :='</email>';
dbms_lob.writeappend(tlob, length(tag), tag);
tag :='<phone>';
dbms_lob.writeappend(tlob, length(tag), tag);
if (c1.PHONE is not null) then
phone := nvl(REGEXP_SUBSTR(c1.PHONE, '\d\d\d\d($|\s)'), ' ');
dbms_lob.writeappend(tlob, length(phone), phone);
end if;
tag :='</phone>';
dbms_lob.writeappend(tlob, length(tag), tag);
tag :='<fullname>';
dbms_lob.writeappend(tlob, length(tag), tag);
if (c1.FIRST_NAME is not null) then
dbms_lob.writeappend(tlob, length(c1.FIRST_NAME), c1.FIRST_NAME);
dbms_lob.writeappend(tlob, length(' '), ' ');
end if;
if (c1.MIDDLE_NAME is not null) then
dbms_lob.writeappend(tlob, length(c1.MIDDLE_NAME), c1.MIDDLE_NAME);
dbms_lob.writeappend(tlob, length(' '), ' ');
end if;
if (c1.LAST_NAME is not null) then
dbms_lob.writeappend(tlob, length(c1.LAST_NAME), c1.LAST_NAME);
end if;
tag :='</fullname>';
dbms_lob.writeappend(tlob, length(tag), tag);
end loop;
end;
/

--list
show errors

exec ctx_ddl.drop_preference('empuds');
begin
ctx_ddl.create_preference('empuds', 'user_datastore');
ctx_ddl.set_attribute('empuds', 'procedure', 'empuds_proc');
ctx_ddl.set_attribute('empuds', 'output_type', 'CLOB');
end;
/

exec ctx_ddl.drop_section_group('namegroup');
begin
ctx_ddl.create_section_group('namegroup', 'BASIC_SECTION_GROUP');
ctx_ddl.add_ndata_section('namegroup', 'fullname', 'fullname');
ctx_ddl.add_ndata_section('namegroup', 'phone', 'phone');
ctx_ddl.add_ndata_section('namegroup', 'email', 'email');
end;
/

-- Need to load nicknames thesaurus
-- ctxload -thes -name nicknames -file dr0thsnames.txt
-- You can find sample nicknames thesaurus file, dr0thsnames.txt, under
-- $ORACLE_HOME/ctx/sample/thes directory.

exec ctx_ddl.drop_preference('ndata_wl');
begin
ctx_ddl.create_preference('NDATA_WL', 'BASIC_WORDLIST');
ctx_ddl.set_attribute('NDATA_WL', 'NDATA_ALTERNATE_SPELLING', 'FALSE');
ctx_ddl.set_attribute('NDATA_WL', 'NDATA_BASE_LETTER', 'TRUE');
ctx_ddl.set_attribute('NDATA_WL', 'NDATA_THESAURUS', 'NICKNAMES');
ctx_ddl.set_attribute('NDATA_WL', 'NDATA_JOIN_PARTICLES',
'de:di:la:da:el:del:qi:abd:los:la:dos:do:an:li:yi:yu:van:jon:un:sai:ben:al');
end;
/

exec ctx_output.start_log('emp_log');
create index name_idx on emp(first_name) indextype is ctxsys.context
parameters ('datastore empuds section group namegroup wordlist ndata_wl
memory 500M');

exec ctx_output.end_log;

-- Now you can do name searches with the following SQL:
var name varchar2(80);
exec :name := 'Jon Blacksmith'

select first_name, middle_name, last_name, phone, email, scr from
(select /*+ FIRST_ROWS */
first_name, middle_name, last_name, phone, email, score(1) scr
from emp
where contains(first_name,
'ndata(phone, '||:name||') OR  ndata(email,'||:name||') OR
ndata(fullname, '||:name||') ',1)>0
order by score(1) desc
) where rownum <= 10;

10 Working With a Thesaurus in Oracle Text

This chapter describes how to improve your query application with a thesaurus. The following topics are discussed in this chapter:

- Overview of Oracle Text Thesaurus Features

- Defining Terms in a Thesaurus

- Using a Thesaurus in a Query Application

- About the Supplied Knowledge Base

Overview of Oracle Text Thesaurus Features

Users of your query application looking for information on a given topic might not know which words have been used in documents that refer to that topic.

Oracle Text enables you to create case-sensitive or case-insensitive thesauruses that define synonym and hierarchical relationships between words and phrases. You can then retrieve documents that contain relevant text by expanding queries to include similar or related terms as defined in the thesaurus.

You can create a thesaurus and load it into the system.

This section contains the following topics.

- Oracle Text Thesaurus Creation and Maintenance

- Using a Case-sensitive Thesaurus

- Using a Case-insensitive Thesaurus

- Default Thesaurus

- Supplied Thesaurus

Note:

Oracle Text thesaurus formats and functionality are compliant with both the ISO-2788 and ANSI Z39.19 (1993) standards.

Oracle Text Thesaurus Creation and Maintenance

Thesauruses and thesaurus entries can be created, modified, deleted, imported, and exported by all Oracle Text users with the CTXAPP role.

This section contains the following topics.

- CTX_THES Package

- Thesaurus Operators

- ctxload Utility

CTX_THES Package

To maintain and browse your thesaurus programatically, you can use the PL/SQL package, CTX_THES. With this package, you can browse terms and hierarchical relationships, add and delete terms, add and remove thesaurus relations, and import and export thesaurus in and out of the thesaurus tables.

Thesaurus Operators

You can also use the thesaurus operators in the CONTAINS clause to expand query terms according to your loaded thesaurus. For example, you can use the SYN operator to expand a term such as dog to its synonyms as follows:

'syn(dog)'

ctxload Utility

The ctxload utility can be used for loading thesauruses from a plain-text file into the thesaurus tables, as well as dumping thesauruses from the tables into output (or dump) files.

The thesaurus dump files created by ctxload can be printed out or used as input for other applications. The dump files can also be used to load a thesaurus into the thesaurus tables. This can be useful for using an existing thesaurus as the basis for creating a new thesaurus.

WARNING:

To ensure sound security practices, Oracle recommends that you enter the password for ctxload using the interactive mode, which prompts you for the user password. Oracle strongly recommends that you do not enter a password on the command line.

Note:

You can also programatically import and export thesaurus in and out of the thesaurus tables using the PL/SQL package CTX_THES procedures IMPORT_THESAURUS and EXPORT_THESAURUS.

Refer to Oracle Text Reference for more information about these procedures.

Using a Case-sensitive Thesaurus

In a case-sensitive thesaurus, terms (words and phrases) are stored exactly as entered. For example, if a term is entered in mixed-case (using either the CTX_THES package or a thesaurus load file), the thesaurus stores the entry in mixed-case.

Note:

To take full advantage of query expansions that result from a case-sensitive thesaurus, your index must also be case-sensitive.

When loading a thesaurus, you can specify that the thesaurus be loaded case-sensitive using the -thescase parameter.

When creating a thesaurus with either CTX_THES.CREATE_THESAURUS or CTX_THES.IMPORT_THESAURUS, you can specify that the thesaurus created be case-sensitive.

In addition, when a case-sensitive thesaurus is specified in a query, the thesaurus lookup uses the query terms exactly as entered in the query. Therefore, queries that use case-sensitive thesauruses allow for a higher level of precision in the query expansion, which helps lookup when and only when you have a case-sensitive index.

For example, a case-sensitive thesaurus is created with different entries for the distinct meanings of the terms Turkey (the country) and turkey (the type of bird). Using the thesaurus, a query for Turkey expands to include only the entries associated with Turkey.

Using a Case-insensitive Thesaurus

In a case-insensitive thesaurus, terms are stored in all-uppercase, regardless of the case in which they were originally entered.

The ctxload program loads a thesaurus in case-insensitive mode by default.

When creating a thesaurus with either CTX_THES.CREATE_THESAURUS or CTX_THES.IMPORT_THESAURUS, the thesaurus is created as case-insensitive by default.

In addition, when a case-insensitive thesaurus is specified in a query, the query terms are converted to all-uppercase for thesaurus lookup. As a result, Oracle Text is unable to distinguish between terms that have different meanings when they are in mixed-case.

For example, a case-insensitive thesaurus is created with different entries for the two distinct meanings of the term TURKEY (the country or the type of bird). Using the thesaurus, a query for either Turkey or turkey is converted to TURKEY for thesaurus lookup and then expanded to include all the entries associated with both meanings.

See Also:

The "ctxload Utility"

Default Thesaurus

If you do not specify a thesaurus by name in a query, by default, the thesaurus operators use a thesaurus named DEFAULT. However, Oracle Text does not provide a DEFAULT thesaurus.

As a result, if you want to use a default thesaurus for the thesaurus operators, you must create a thesaurus named DEFAULT. You can create the thesaurus through any of the thesaurus creation methods supported by Oracle Text:

- CTX_THES.CREATE_THESAURUS (PL/SQL)

- CTX_THES.IMPORT_THESAURUS (PL/SQL)

- ctxload utility

See Also:

Oracle Text Reference to learn more about using ctxload and the CTX_THES package, and "ctxload Utility" in this chapter

Supplied Thesaurus

Although Oracle Text does not provide a default thesaurus, Oracle Text does supply a thesaurus, in the form of a file that you load with ctxload, that can be used to create a general-purpose, English-language thesaurus.

The thesaurus load file can be used to create a default thesaurus for Oracle Text, or it can be used as the basis for creating thesauruses tailored to a specific subject or range of subjects.

This section contains the following topics.

- Supplied Thesaurus Structure and Content

- Supplied Thesaurus Location

See Also:

Oracle Text Reference to learn more about using ctxload and the CTX_THES package, and "ctxload Utility" in this chapter

Supplied Thesaurus Structure and Content

The supplied thesaurus is similar to a traditional thesaurus, such as Roget's Thesaurus, in that it provides a list of synonymous and semantically related terms.

The supplied thesaurus provides additional value by organizing the terms into a hierarchy that defines real-world, practical relationships between narrower terms and their broader terms.

Additionally, cross-references are established between terms in different areas of the hierarchy.

Supplied Thesaurus Location

The exact name and location of the thesaurus load file is operating system dependent; however, the file is generally named dr0thsus (with an appropriate extension for text files) and is generally located in the following directory structure:

<Oracle_home_directory>
<interMedia_Text_directory>
sample
thes

See Also:

Oracle Database Installation Guide for the installation documentation specific to your operating system for more information about the directory structure of Oracle Text

Defining Terms in a Thesaurus

You can create synonyms, related terms, and hierarchical relationships with a thesaurus.

This section contains the following topics.

- Defining Synonyms

- Defining Hierarchical Relations

Defining Synonyms

If you have a thesaurus of computer science terms, you might define a synonym for the term XML as extensible markup language. This enables queries on either of these terms to return the same documents.

XML

SYN Extensible Markup Language

You can thus use the SYN operator to expand XML into its synonyms:

'SYN(XML)'

is expanded to:

'XML, Extensible Markup Language'

Defining Hierarchical Relations

If your document set is made up of news articles, you can use a thesaurus to define a hierarchy of geographical terms. Consider the following hierarchy that describes a geographical hierarchy for the U.S state of California:

California
NT Northern California
NT San Francisco
NT San Jose
NT Central Valley
NT Fresno
NT Southern California
NT Los Angeles

You can thus use the NT operator to expand a query on California as follows:

'NT(California)'

expands to:

'California, Northern California, San Francisco, San Jose, Central Valley,
Fresno, Southern California, Los Angeles'

The resulting hitlist shows all documents related to the U.S. state of California regions and cities.

Using a Thesaurus in a Query Application

Defining a custom thesaurus enables you to process queries more intelligently. Because users of your application might not know which words represent a topic, you can define synonyms or narrower terms for likely query terms. You can use the thesaurus operators to expand your query into your thesaurus terms.

There are two ways to enhance your query application with a custom thesaurus so that you can process queries more intelligently:

- Load your custom thesaurus and enter queries with thesaurus operators

- Augment the knowledge base with your custom thesaurus (English only) and use the ABOUT operator to expand your query.

Each approach has its advantages and disadvantages.

This section contains the following topics.

- Loading a Custom Thesaurus and Issuing Thesaurus-based Queries

- Augmenting Knowledge Base with Custom Thesaurus

Loading a Custom Thesaurus and Issuing Thesaurus-based Queries

You can build and load a custom thesaurus.

The advantage of using this method is that you can modify the thesaurus after indexing.

The limitation of this method is that you must use thesaurus expansion operators in your query. Long queries can cause extra overhead in the thesaurus expansion and slow your query down.

To build a custom thesaurus, follow these steps:

1. Create your thesaurus. See "Defining Terms in a Thesaurus".

2. Load thesaurus with ctxload. The following example imports a thesaurus named tech_doc from an import file named tech_thesaurus.txt:

ctxload -thes -name tech_doc -file tech_thesaurus.txt

3. At the prompt, enter username and password. To ensure security, do not enter a password at the command line.

4. Use THES operators to query. For example, you can find all documents that contain XML and its synonyms as defined in tech_doc:

'SYN(XML, tech_doc)'

Augmenting Knowledge Base with Custom Thesaurus

You can add your custom thesaurus to a branch in the existing knowledge base. The knowledge base is a hierarchical tree of concepts used for theme indexing, ABOUT queries, and deriving themes for document services.

When you augment the existing knowledge base with your new thesaurus, you query with the ABOUT operator which implicitly expands to synonyms and narrower terms. You do not query with the thesaurus operators.

To augment the existing knowledge base with your custom thesaurus, follow these steps:

1. Create your custom thesaurus, linking new terms to existing knowledge base terms. See "Defining Terms in a Thesaurus" and "Linking New Terms to Existing Terms".

2. Load thesaurus by one of the following methods:

- Using the ctxload utility. See "Loading a Thesaurus with ctxload".

- Using the PL/SQL procedure CTX_THES.IMPORT_THESAURUS. See "Loading a Thesaurus with PL/SQL procedure CTX_THES.IMPORT_THESAURUS".

3. Compile the loaded thesaurus with ctxkbtc compiler. Refer to "Compiling a Loaded Thesaurus".

4. Index your documents. By default the system creates a theme component to your index.

5. Use ABOUT operator to query. For example, to find all documents that are related to the term politics including any synonyms or narrower terms as defined in the knowledge base, enter the query:

'about(politics)'

Advantage

Compiling your custom thesaurus with the existing knowledge base before indexing enables faster and simpler queries with the ABOUT operator. Document services can also take full advantage of the customized information for creating theme summaries and Gists.

Limitations

Use of the ABOUT operator requires a theme component in the index, which requires slightly more disk space. You must also define the thesaurus before indexing your documents. If you make any change to the thesaurus, you must recompile your thesaurus and re-index your documents.

Linking New Terms to Existing Terms

When adding terms to the knowledge base, Oracle recommends that new terms be linked to one of the categories in the knowledge base for best results in theme proving.

See Also:

Oracle Text Reference for more information about the supplied English knowledge base

If new terms are kept completely separate from existing categories, fewer themes from new terms will be proven. The result of this is poor precision and recall with ABOUT queries as well as poor quality of gists and theme highlighting.

You link new terms to existing terms by making an existing term the broader term for the new terms.

Example: Linking New Terms to Existing Terms

You purchase a medical thesaurus medthes containing a a hierarchy of medical terms. The four top terms in the thesaurus are as follows:

- Anesthesia and Analgesia

- Anti-Allergic and Respiratory System Agents

- Anti-Inflammatory Agents, Antirheumatic Agents, and Inflammation Mediators

- Antineoplastic and Immunosuppressive Agents

To link these terms to the existing knowledge base, add the following entries to the medical thesaurus to map the new terms to the existing health and medicine branch:

health and medicine
NT Anesthesia and Analgesia
NT Anti-Allergic and Respiratory System Agents
NT Anti-Inflamammatory Agents, Antirheumatic Agents, and Inflamation Mediators
NT Antineoplastic and Immunosuppressive Agents

Loading a Thesaurus with ctxload

Assuming the medical thesaurus is in a file called med.thes, you load the thesaurus as medthes with ctxload as follows:

ctxload -thes -thescase y -name medthes -file med.thes -user ctxsys

When you enter the ctxload command line, you are prompted for the user password. For best security practices, never enter the password at the command line. Alternatively, you may omit the -user and let ctxload prompt you for username and password, respectively.

Loading a Thesaurus with PL/SQL procedure CTX_THES.IMPORT_THESAURUS

The following example creates a case-sensitive thesaurus named mythesaurus and imports the thesaurus content present in myclob into the Oracle Text thesaurus tables:

declare
myclob clob;
begin
myclob := to_clob('peking SYN beijing BT capital country NT beijing tokyo');
ctx_thes.import_thesaurus(‘mythesaurus', myclob, ‘Y');
end;

The format of the thesaurus to be imported (myclob in this example) should be the same as used by the ctxload utility. If the format of the thesaurus to be imported is not correct, then IMPORT_THESAURUS raises an exception.

Compiling a Loaded Thesaurus

To link the loaded thesaurus medthes to the knowledge base, use ctxkbtc as follows:

ctxkbtc -user ctxsys -name medthes

When you enter the ctxkbtc command line, you are prompted for the user password. As with ctxload, for best security practices, do not enter the password at the command line.

WARNING:

In order to ensure sound security practices, Oracle recommends that you enter the password for ctxload and ctxkbtc using the interactive mode, which prompts you for the user password. Oracle strongly recommends that you do not enter a password on the command line.

About the Supplied Knowledge Base

Oracle Text supplies a knowledge base for English and French. The supplied knowledge contains the information used to perform theme analysis. Theme analysis includes theme indexing, ABOUT queries, and theme extraction with the CTX_DOC package.

The knowledge base is a hierarchical tree of concepts and categories. It has six main branches:

- Science and technology

- Business and economics

- Government and military

- Social environment

- Geography

- Abstract ideas and concepts

See Also:

Oracle Text Reference for the breakdown of the category hierarchy

The supplied knowledge base is like a thesaurus in that it is hierarchical and contains broader term, narrower term, and related term information. As such, you can improve the accuracy of theme analysis by augmenting the knowledge base with your industry-specific thesaurus by linking new terms to existing terms.

See Also:

"Augmenting Knowledge Base with Custom Thesaurus"

You can also extend theme functionality to other languages by compiling a language-specific thesaurus into a knowledge base.

See Also:

"Adding a Language-Specific Knowledge Base"

Knowledge bases can be in any single-byte character set. Supplied knowledge bases are in WE8ISO8859P1. You can store an extended knowledge base in another character set such as US7ASCII.

This section contains the following topics.

- Adding a Language-Specific Knowledge Base

- Limitations for Adding Knowledge Bases

Adding a Language-Specific Knowledge Base

You can extend theme functionality to languages other than English or French by loading your own knowledge base for any single-byte whitespace delimited language, including Spanish.

Theme functionality includes theme indexing, ABOUT queries, theme highlighting, and the generation of themes, gists, and theme summaries with CTX_DOC.

You extend theme functionality by adding a user-defined knowledge base. For example, you can create a Spanish knowledge base from a Spanish thesaurus.

To load your language-specific knowledge base, follow these steps:

1. Load your custom thesaurus using ctxload. Refer to "Loading a Thesaurus with ctxload".

2. Set NLS_LANG so that the language portion is the target language. The charset portion must be a single-byte character set.

3. Compile the loaded thesaurus using ctxkbtc as follows:

ctxkbtc -user ctxsys -name my_lang_thes

Enter the password for -user when prompted. Refer to "Compiling a Loaded Thesaurus".

This statement compiles your language-specific knowledge base from the loaded thesaurus.

To use this knowledge base for theme analysis during indexing and ABOUT queries, specify the NLS_LANG language as the THEME_LANGUAGE attribute value for the BASIC_LEXER preference.

Limitations for Adding Knowledge Bases

The following limitations apply for adding knowledge bases:

- Oracle supplies knowledge bases in English and French only. You must provide your own thesaurus for any other language.

- You can only add knowledge bases for languages with single-byte character sets. You cannot create a knowledge base for languages which can be expressed only in multibyte character sets. If the database is a multibyte universal character set, such as UTF-8, the NLS_LANG parameter must still be set to a compatible single-byte character set when compiling the thesaurus.

- Adding a knowledge base works best for whitespace delimited languages.

- You can have at most one knowledge base for each NLS_LANG language.

- Obtaining hierarchical query feedback information such as broader terms, narrower terms and related terms does not work in languages other than English and French. In other languages, the knowledge bases are derived entirely from your thesauruses. In such cases, Oracle recommends that you obtain hierarchical information directly from your thesauruses.

See Also:

Oracle Text Reference for more information about theme indexing, ABOUT queries, using the CTX_DOC package, and the supplied English knowledge base

11 Using XML Query Result Set Interface

This chapter describes how to use the XML Query Result Set Interface.

This chapter contains these topics:

- Overview of the XML Query Result Set Interface

- Using the XML Query Result Set Interface

- Creating XML-Only Applications with Oracle Text

- Example of a Result Set Descriptor

Overview of the XML Query Result Set Interface

The XML Query Result Set Interface (RSI) enables you to perform queries in XML and return results as XML, avoiding the SQL layer and requirement to work within SELECT semantics. The Result Set Interface uses a simple text query and an XML result set descriptor, where the hitlist is returned in XML according to the result set descriptor. The XML Query Result Set Interface uses SDATA sections for grouping and counting.

A page of search results in applications can consist of many disparate elements such as metadata of the first few documents, total hit counts, per-word hit counts, and so on. Each extra call takes time to reparse the query and look up index metadata. Additionally, some search operations such as iterative query refinement are difficult for SQL. If it is even possible to construct a SQL statement to produce the desired results, such SQL is usually suboptimal.

The XML Query Result Set Interface is able to produce the various kinds of data needed for a page of search results all at once, thus improving performance by sharing overhead. The Result Set Interface can also return data views that are difficult to express in SQL.

Using the XML Query Result Set Interface

The CTX_QUERY.RESULT_SET() API enables you to obtain query results with a single query, rather than running multiple CONTAINS() queries to achieve the same result. For example, in order to display a search result page, the following information needs to be obtained first:

- top 20 hit list sorted by date and relevancy

- total number of hits for the given Text query

- counts group by publication date

- counts group by author

Assume the following table definition for storing documents to be searched:

create table docs (
docid    number,
author   varchar2(30),
pubdate  date,
title    varchar2(60),  doc      clob);

Assume the following Oracle Text Index definition:

create index docidx on docs(doc) indextype is ctxsys.context
filter by author, pubdate, title
order by pubdate;

With these definitions, you can obtain the four pieces of information for displaying the search result page by issuing four SQL statements:

-- Get top 20 hits sorted by date and relevancy
select * from
(select /*+ first_rows */ rowid, title, author, pubdate
from docs where contains(doc, 'oracle',1)>0
order by pubdate desc, score(1) desc)
where rownum < 21;

-- Get total number of hits for the given Text query
select count(*) from docs where contains(doc, 'oracle',1)>0;

-- Get counts group by publication date
select pubdate, count(*) from docs where contains(doc, 'oracle',1)>0
group by pubdate;

-- Get counts group by author
select author, count(*) from docs where contains(doc, 'oracle',1)>0 group by author;

As you can see, using separate SQL statements results in a resource-intensive query, as you run the same query four times. However, by using CTX_QUERY.RESULT_SET(), you can enter all this information in one single Oracle Text query:

declare
rs clob;
begin
dbms_lob.createtemporary(rs, true, dbms_lob.session);
ctx_query.result_set('docidx', 'oracle text performance tuning', '
<ctx_result_set_descriptor>
<count/>
<hitlist start_hit_num="1" end_hit_num="20" order="pubDate desc,
score desc">
<score/>
<rowid/>
<sdata name="title"/>
<sdata name="author"/>
<sdata name="pubDate"/>
</hitlist>
<group sdata="pubDate">
<count/>
</group>
<group sdata="author">
<count/>
</group>
</ctx_result_set_descriptor>
', rs);

-- Put in your code here to process the Output Result Set XML
dbms_lob.freetemporary(rs);
exception
when others then
dbms_lob.freetemporary(rs);
raise;
end;
/

The result set output will be XML containing all the necessary information required to construct the search result page:

<ctx_result_set>
<hitlist>
<hit>
<score>90</score>
<rowid>AAAPoEAABAAAMWsAAC</rowid>
<sdata name="TITLE"> Article 8 </sdata>
<sdata name="AUTHOR">John</sdata>
<sdata name="PUBDATE">2001-01-03 00:00:00</sdata>
</hit>
<hit>
<score>86</score>
<rowid>AAAPoEAABAAAMWsAAG</rowid>
<sdata name="TITLE"> Article 20 </sdata>
<sdata name="AUTHOR">John</sdata>
<sdata name="PUBDATE">2001-01-03 00:00:00</sdata>
</hit>
<hit>
<score>78</score>
<rowid>AAAPoEAABAAAMWsAAK</rowid>
<sdata name="TITLE"> Article 17 </sdata>
<sdata name="AUTHOR">John</sdata>
<sdata name="PUBDATE">2001-01-03 00:00:00</sdata>
</hit>
<hit>
<score>77</score>
<rowid>AAAPoEAABAAAMWsAAO</rowid>
<sdata name="TITLE"> Article 37 </sdata>
<sdata name="AUTHOR">John</sdata>
<sdata name="PUBDATE">2001-01-03 00:00:00</sdata>
</hit>
...
<hit>
<score>72</score>
<rowid>AAAPoEAABAAAMWsAAS</rowid>
<sdata name="TITLE"> Article 56 </sdata>
<sdata name="AUTHOR">John</sdata>
<sdata name="PUBDATE">2001-01-03 00:00:00</sdata>
</hit>
</hitlist>

<count>100</count>

<groups sdata="PUBDATE">
<group value="2001-01-01 00:00:00"><count>25</count></group>
<group value="2001-01-02 00:00:00"><count>50</count></group>
<group value="2001-01-03 00:00:00"><count>25</count></group>
</groups>

<groups sdata="AUTHOR">
<group value="John"><count>50</count></group>
<group value="Mike"><count>25</count></group>
<group value="Steve"><count>25</count></group>
</groups>

</ctx_result_set>

See Also:

Oracle Text Reference for syntax details and more information on CTX_QUERY.RESULT_SET

Creating XML-Only Applications with Oracle Text

Although it is common to create applications using SQL SELECT statements with the CONTAINS clause, this is not always the most efficient way of working. An alternative method is to use the XML-based Result Set Interface. The advantage of doing this is that it is easy to obtain summary information (such as the total number of hits) without having to fetch all the results of the query.

To use the Result Set Interface, you specify a Result Set Descriptor, or RSD. This declares the information which is to be returned. The information to be returned can consist of:

- The total result count of the query

- A hitlist

- Summary information over SDATA fields.

In turn, the hitlist consists of repeating elements, each of which may contain:

- The rowid of the hit

- SDATA fields from the hit

See Also:

"Example of a Result Set Descriptor"

Example of a Result Set Descriptor

The example in this section shows how to use a Result Set Descriptor (or RSD). The following example requests a hitlist with the top 10 hits (ordered by score), plus the count of the total number of results.

<ctx_result_set_descriptor>
<hitlist start_hit_num="1" end_hit_num="10" order="SCORE DESC">
<rowid />
<sdata name="title" />
<sdata name="author" />
<sdata name="articledate" />
<snippet radius="20" max_length="160" starttag="&lt;b&gt;" endtag="&lt;/b&gt;" />
</hitlist>
<count />
</ctx_result_set_descriptor>

For each hit, you are requesting the rowid (which you could use to fetch further information about the row, if necessary), the contents of the SDATA fields or columns called title, author and articledate, and a snippet (which is a short summary with keywords highlighted, in this case by <b>...</b>).

12 Administering Oracle Text

This chapter describes Oracle Text administration.

The following topics are covered:

- Oracle Text Users and Roles

- DML Queue

- The CTX_OUTPUT Package

- The CTX_REPORT Package

- Text Manager in Oracle Enterprise Manager

- Servers and Indexing

- Database Feature Usage Tracking in Oracle Enterprise Manager

- Oracle Text on Oracle Real Application Clusters

Oracle Text Users and Roles

While any user can create an Oracle Text index and enter a CONTAINS query, Oracle Text provides the CTXSYS user for administration and the CTXAPP role for application developers.

This section contains the following sections:

- CTXSYS User

- CTXAPP Role

- Granting Roles and Privileges to Users

CTXSYS User

The CTXSYS user is created during installation time. CTXSYS can do the following:

- View all indexes

- Sync all indexes

- Run ctxkbtc, the knowledge base extension compiler

- Query all system-defined views

- Perform all the tasks of a user with the CTXAPP role

Note:

In earlier releases of Oracle Text, CTXSYS had SYSDBA privileges, and only CTXSYS could perform certain functions, such as modifying system-defined preferences or setting system parameters.

CTXAPP Role

The CTXAPP role is a system-defined role that enables users to do the following:

- Create and delete Oracle Text preferences

- Use the Oracle Text PL/SQL packages

Any user can create an Oracle Text index and enter a Text query. The CTXAPP role enables users to create preferences and use the PL/SQL packages.

Granting Roles and Privileges to Users

The system uses the standard SQL model for granting roles to users. To grant a Text role to a user, use the GRANT statement.

In addition, to allow application developers to call procedures in the Oracle Text PL/SQL packages, you must explicitly grant to each user EXECUTE privileges for the Oracle Text package.

See Also:

"Creating an Oracle Text User"

DML Queue

When there are inserts, updates, or deletes to documents in your base table, the DML queue stores the requests for documents waiting to be indexed. When you synchronize the index with CTX_DDL.SYNC_INDEX, requests are removed from this queue.

Pending DML requests can be queried with the CTX_PENDING and CTX_USER_PENDING views.

DML errors can be queried with the CTX_INDEX_ERRORS or CTX_USER_INDEX_ERRORS view.

See Also:

Oracle Text Reference for more information about these views

The CTX_OUTPUT Package

Use the CTX_OUTPUT PL/SQL package to log indexing and document service requests.

See Also:

Oracle Text Reference for more information about this package

The CTX_REPORT Package

Use the CTX_REPORT package to produce reports on indexes and queries. These reports can help you fine-tune or troubleshoot your applications.

See Also:

Oracle Text Reference for more information about this package

The CTX_REPORT package contains the following procedures:

CTX_REPORT.DESCRIBE_INDEX

CTX_REPORT.DESCRIBE_POLICY

These procedures create reports that describe an existing index or policy, including the settings of the index metadata, the indexing objects used, the settings of the attributes of the objects, and (for CTX_REPORT.DESCRIBE_INDEX) index partition information, if any. These procedures are especially useful for diagnosing index-related problems.

This is sample output from DESCRIBE_INDEX, run on a simple context index:

=================================================================
INDEX DESCRIPTION
=================================================================
index name:                      "DR_TEST"."TDRBPRX0"
index id:                        1160
index type:                      context
base table:                      "DR_TEST"."TDRBPR"
primary key column:              ID
text column:                     TEXT2
text column type:                VARCHAR2(80)
language column:
format column:
charset column:
=================================================================
INDEX OBJECTS
=================================================================
datastore:                       DIRECT_DATASTORE
filter:                          NULL_FILTER
section group:                   NULL_SECTION_GROUP
lexer:                           BASIC_LEXER
wordlist:                        BASIC_WORDLIST
stemmer:                         ENGLISH
fuzzy_match:                     GENERIC
stoplist:                        BASIC_STOPLIST
stop_word:                       teststopword
storage:                         BASIC_STORAGE
r_table_clause:                  lob (data) store as (cache)
i_index_clause:                  compress 2

CTX_REPORT.CREATE_INDEX_SCRIPT

CTX_REPORT.CREATE_POLICY_SCRIPT

CREATE_INDEX_SCRIPT creates a SQL*Plus script that can create a duplicate of a given text index. Use this when you have an index but you do not have the original script (if any) that was used to create this index, and you want to be able to re-create the index. For example, if you accidentally drop a script, CREATE_INDEX_SCRIPT can re-create it. Likewise, CREATE_INDEX_SCRIPT can be useful if you have inherited indexes from another user but not the scripts that created them.

CREATE_POLICY_SCRIPT does the same thing as CREATE_INDEX_SCRIPT, except that it enables you to re-create a policy instead of an index.

This is sample output from CREATE_INDEX_SCRIPT, run on a simple context index (not a complete listing):

begin
ctx_ddl.create_preference('"TDRBPRX0_DST"','DIRECT_DATASTORE');
end;
/
...
/
begin
ctx_ddl.create_section_group('"TDRBPRX0_SGP"','NULL_SECTION_GROUP');
end;
/
...
begin
ctx_ddl.create_preference('"TDRBPRX0_WDL"','BASIC_WORDLIST');
ctx_ddl.set_attribute('"TDRBPRX0_WDL"','STEMMER','ENGLISH');
ctx_ddl.set_attribute('"TDRBPRX0_WDL"','FUZZY_MATCH','GENERIC');
end;
/
begin
ctx_ddl.create_stoplist('"TDRBPRX0_SPL"','BASIC_STOPLIST');
ctx_ddl.add_stopword('"TDRBPRX0_SPL"','teststopword');
end;
/
...
/
begin
ctx_output.start_log('TDRBPRX0_LOG');
end;
/
create index "DR_TEST"."TDRBPRX0"
on "DR_TEST"."TDRBPR"
("TEXT2")
indextype is ctxsys.context
parameters('
datastore       "TDRBPRX0_DST"
filter          "TDRBPRX0_FIL"
section group   "TDRBPRX0_SGP"
lexer           "TDRBPRX0_LEX"
wordlist        "TDRBPRX0_WDL"
stoplist        "TDRBPRX0_SPL"
storage         "TDRBPRX0_STO"
')
/

CTX_REPORT.INDEX_SIZE

This procedure creates a report showing the names of the internal index objects, along with their tablespaces, allocated sizes, and used sizes. It is useful for DBAs who may need to monitor the size of their indexes (for example, when disk space is at a premium).

Sample output from this procedure looks like this (partial listing):

=================================================================
INDEX SIZE FOR DR_TEST.TDRBPRX10
=================================================================
TABLE:                          DR_TEST.DR$TDRBPRX10$I
TABLESPACE NAME:                DRSYS
BLOCKS ALLOCATED:                                            4
BLOCKS USED:                                                 1
BYTES ALLOCATED:                               8,192 (8.00 KB)
BYTES USED:                                    2,048 (2.00 KB)

INDEX (LOB):                    DR_TEST.SYS_IL0000023161C00006$$
TABLE NAME:                     DR_TEST.DR$TDRBPRX10$I
TABLESPACE NAME:                DRSYS
BLOCKS ALLOCATED:                                            5
BLOCKS USED:                                                 2
BYTES ALLOCATED:                             10,240 (10.00 KB)
BYTES USED:                                    4,096 (4.00 KB)

INDEX (NORMAL):                 DR_TEST.DR$TDRBPRX10$X
TABLE NAME:                     DR_TEST.DR$TDRBPRX10$I
TABLESPACE NAME:                DRSYS
BLOCKS ALLOCATED:                                            4
BLOCKS USED:                                                 2
BYTES ALLOCATED:                               8,192 (8.00 KB)
BYTES USED:                                    4,096 (4.00 KB)

CTX_REPORT.INDEX_STATS

INDEX_STATS produces a variety of calculated statistics about an index, such as how many documents are indexed, how many unique tokens the index contains, average size of its tokens, fragmentation information for the index, and so on. An example of a use of INDEX_STATS might be in optimizing stoplists.

See Oracle Text Reference for an example of the output of this procedure.

CTX_REPORT.QUERY_LOG_SUMMARY

This procedure creates a report of logged queries, which you can use to perform simple analyses. With query analysis, you can find out:

- which queries were made

- which queries were successful

- which queries were unsuccessful

- how many times each query was made

You can combine these factors in various ways, such as determining the 50 most frequent unsuccessful queries made by your application.

See Oracle Text Reference for an example of the output of this procedure.

CTX_REPORT.TOKEN_INFO

TOKEN_INFO is used mainly to diagnose query problems; for instance, to check that index data is not corrupted. As an example, you can use it to find out which documents are producing unexpected or bad tokens.

CTX_REPORT.TOKEN_TYPE

This is a lookup function, used mainly as input to other functions (CTX_DDL.OPTIMIZE_INDEX, CTX_REPORT.TOKEN_INFO, and so on).

Text Manager in Oracle Enterprise Manager

Oracle Enterprise Manager provides Text Manager for configuring, maintaining, and administering Oracle Text indexes. With Text Manager you can perform all of the basic configuration and administration tasks for Oracle Text indexes. You can monitor the overall health of Text indexes for a single Oracle database instance or for the Oracle Real Application Clusters environment. Text Manager provides summaries of critical information and enables you to drill down to the level of detail that you want, to resolve issues, and to understand any actions that may need to occur. You access Text Manager by clicking the Schema tab from the database home page in Oracle Enterprise Manager, and then selecting Text Indexes under the Text Manager group. On the Text Indexes page, select an index name and click View to see information and attributes for that index.

The Text Indexes page shows the jobs that are in progress, scheduled within the last seven days, or are experiencing problems. From this page you can go to the Job Scheduler to see a summary of all jobs for this database instance, and to manage selected jobs. The online help in Oracle Enterprise Manager provides details and procedures for using each Text Manager feature.

This section contains the following sections:

- Using Text Manager

- Viewing General Information for a Text Index

- Checking Text Index Health

Note:

You cannot create an Oracle Text index with Text Manager. Use the CREATE INDEX statement to create an Oracle Text index as described in Indexing with Oracle Text under Creating Oracle Text Indexes.

Using Text Manager

From the main Text Manager page, you can perform the following actions on the selected index from the Actions list:

- Synchronize

- Optimize

- Rebuild

- Resume Failed Operation

- Show Logs

- Show Errors

You can also schedule jobs for the specified index.

To access Text Manager:

1. Log on to the database with a user account that is authorized to access Cloud Control. For example, this could be SYS or SYSTEM, with the password that you specified during database installation.

Cloud Control displays the Database Home page.

2. Select the Schema tab from the Database Home page.

3. Click Text Indexes located under Text Manager.

The Text Indexes page appears with a list of Text indexes for this database instance.

When you select a Text index from the Text Indexes page, options become available for that index for you to edit or perform actions. For example, to configure attributes for searching, click Edit for the selected index. From the Edit Text Index page, you can set attributes, including: Wild Card Maximum Term, Fuzzy Score, and Number of Fuzzy Expansions. You can change index and partition names, as well as specify settings for URL_DATASTORE in addition to other options.

Viewing General Information for a Text Index

You can use the View Text Index page to see general information about a specific index: index type, parallel degree, synchronization mode, wild card limit, fuzzy score, fuzzy numeric result, datastore, and so forth. Information about any partitions on the index is also available.

To view general information for a Text index:

- From the Text Indexes page, click the name of the index in the list of Text indexes.
The View Text Index page opens with the General tab selected.

From here you can select actions to perform maintenance tasks.

Checking Text Index Health

You use the Text Indexes page in Text Manager to see the list of Text indexes and general health of the Text indexes for the database instance to help you understand any critical actions that may need to be taken in order to make sure that the entire application is performing properly. Information is displayed such as the status of the indexes and jobs submitted by users during the last seven days. Key information about the Text indexes is also displayed in a tabular form.

Use the Text Indexes page to see:

- The number of Text indexes that contain invalid partitions, and which are, therefore, invalid. The number of partitions that are invalid, if any, for all Text indexes is also shown.

- The number of indexes that are in an in-progress state, and the number of partitions, if any, that are in an in-progress state.

- The number of indexes where all partitions are valid and no activity is in progress.

- Sum total of the Text indexes found for this database instance.

Additionally, use the Text Indexes page to see the index type for each Text index, the owner, the number of documents that are not synchronized, total number of documents, and percentage of fragmentation.

You select a Text index from the list and then options become available for that index for you to edit or perform actions.

Servers and Indexing

You index documents and enter queries with standard SQL. No server is needed for performing batch DML. You can synchronize the CONTEXT index with the CTX_DDL.SYNC_INDEX procedure, or from Text Manager in Oracle Enterprise Manager.

See Also:

Indexing with Oracle Text for more information about indexing and index synchronization

Database Feature Usage Tracking in Oracle Enterprise Manager

Database Feature Usage statistics in Oracle Enterprise Manager provide an approximation of how often various database features are used. Tracking this information is potentially useful for application development as well as for auditing. You access Database Feature Usage by clicking the Server tab in Oracle Enterprise Manager, and then selecting Database Feature Usage under the Database Configuration group.

The following information is gathered for Oracle Text:

- Package Usage Statistics

- Index Usage Statistics

- SQL Operator Usage Statistics

For package usage statistics, Database Feature Usage captures information about how often, if ever, and when the following packages have been used.

- CTX_ADM

- CTX_CLS

- CTX_DDL

- CTX_DOC

- CTX_OUTPUT

- CTX_QUERY

- CTX_REPORT

- CTX_THES

- CTX_ULEXER

For index usage statistics, Database Feature Usage captures the number of existing indexes in the database. The statistics are captured separately for each index type: CONTEXT, CTXCAT, and CTXRULE.

For SQL operator usage statistics, Database Feature Usage captures whether the user has ever used the CONTAINS, CATSEARCH, and MATCHES operators.

Note:

The feature usage tracking statistics might not be 100% accurate.

Oracle Text on Oracle Real Application Clusters

Oracle Text queries can be parallelized across Oracle RAC nodes for maximum throughput and performance for OLAP applications. You can manage Oracle Text indexes on Oracle RAC nodes with Text Manager in Oracle Enterprise Manager as described in the previous section "Text Manager in Oracle Enterprise Manager".

See Also:

"Parallelizing Queries Across Oracle RAC Nodes"

13 Migrating Oracle Text Applications

When you upgrade to a new release of Oracle Database, there may be issues relating to migrating your applications from earlier releases of Oracle Text. Where applicable, Oracle provides information about any needed migration steps to move Oracle Text applications into the new release.

This chapter contains the following sections:

- Oracle Text and Rolling Upgrade with Logical Standby

- About Migrating to Oracle Text 12c Release 1 (12.1)

- About Migrating to Oracle Text 11g Release 2 (11.2)

- About Migrating to Oracle Text 11g Release 1 (11.1)

- About Migrating to Oracle Text 10g Release 2 (10.2)

See Also:

Oracle Database Upgrade Guide for information on upgrading Oracle Database and topics about migrating applications

Oracle Text and Rolling Upgrade with Logical Standby

You can use a logical standby database to perform a rolling upgrade of Oracle Database. During a rolling upgrade, you can run different releases of Oracle Database on the primary and logical standby databases while you upgrade your databases, one at a time, incurring minimal downtime on the primary database. Oracle Text takes full advantage of upgrading Text indexes during a rolling upgrade.

All CTX PL/SQL procedures are fully replicated to the standby database and, therefore, are upgraded, except with certain limitations, as described, for these procedures:

- CTX_DDL PL/SQL Procedures

- CTX_OUTPUT PL/SQL Procedures

- CTX_DOC PL/SQL Procedures

See Also:

Oracle Data Guard Concepts and Administration for information on creating a logical standby database to perform rolling upgrades

CTX_DDL PL/SQL Procedures

Oracle Database uses rowids internally for the construction of indexes. The following CTX_DDL procedures are not fully replicated to the standby:

- ADD_MDATA

- REMOVE_MDATA

CTX_OUTPUT PL/SQL Procedures

Only CTX_OUTPUT.ENABLE_QUERY_STATS and CTX_OUTPUT.DISABLE_QUERY_STATS are replicated. This means that if Oracle Text logging is enabled on the primary database before running an operation that causes logging, then the operation will run with logging on the primary database, but will run without logging on the secondary database.

CTX_DOC PL/SQL Procedures

When the following CTX_DOC procedures are used with Oracle Text Result Tables, the data stored in the tables is replicated. When these procedures are used without Result Tables, they are not replicated.

- CTX_DOC.SET_KEY_TYPE

- CTX_DOC.FILTER

- CTX_DOC.GIST

- CTX_DOC.MARKUP

- CTX_DOC.TOKENS

- CTX_DOC.THEMES

- CTX_DOC.HIGHLIGHT

- CTX_DOC.FILTER_CLOB_QUERY

- CTX_DOC.MARKUP_CLOB_QUERY

- CTX_DOC.HIGHLIGHT_CLOB_QUERY

See Also:

Oracle Data Guard Concepts and Administration for information on performing a rolling upgrade for minimal downtime on the primary database

About Migrating to Oracle Text 12c Release 1 (12.1)

No changes to applications are required when migrating your applications to Oracle Text 12c Release 1 (12.1).

About Migrating to Oracle Text 11g Release 2 (11.2)

No changes to applications are required when migrating your applications to Oracle Text 11g Release 2 (11.2).

About Migrating to Oracle Text 11g Release 1 (11.1)

No changes to applications are required when migrating your applications to Oracle Text 11g Release 1 (11.1).

About Migrating to Oracle Text 10g Release 2 (10.2)

This section covers issues relating to migrating your applications to Oracle Text 10g Release 2 (10.2). This information is provided for those users who may be upgrading from the next-to-last release of Oracle Text and who want to know what migration steps were required to upgrade to the last release.

- Filter Comparison (INSO_FILTER versus AUTO_FILTER)

- About Migrating to the AUTO_FILTER Filter Type

Filter Comparison (INSO_FILTER versus AUTO_FILTER)

With Oracle Text 11g Release 1 and later, the INSO_FILTER filter type has been replaced by the AUTO_FILTER filter type. To maintain compatibility with existing Oracle Text applications, INSO_FILTER functionality is supported by AUTO_FILTER, and the INSO_FILTER filter type is being retained, although its behavior has been changed to match that of AUTO_FILTER.

For most Text applications, the change in filter types has no significant effect, and most applications to not need to be changed. You do not need to take any steps to migrate to the new filter type. The most significant differences produced by this change are as follows:

- AUTO_FILTER supports a different set of document types than INSO_FILTER. For a list of supported document types, see the Supported File Formats appendix of Oracle Text Reference.

- Display characteristics of HTML output from the new filter may differ from those output by the old filter.

- A different set of platforms support the AUTO_FILTER type than support INSO_FILTER. For a list of supported platforms, see the Supported File Formats appendix of Oracle Text Reference.

Along with the change from INSO_FILTER to AUTO_FILTER, several related changes are also part of the filter migration:

- The INSO_TIMEOUT and INSO_OUTPUT_FORMATTING attributes of MAIL_FILTER have been replaced by the AUTO_FILTER_TIMEOUT and AUTO_FILTER_OUTPUT_FORMATTING attributes, respectively.

- The INSOFILTER directive used in the mail configuration file of MAIL_FILTER has been replaced with the AUTO_FILTER directive.

- The PL/SQL constant TRACE_IDX_INSO_FILTER for tracing, used in procedures such as CTX_OUTPUT.ADD_TRACE, has been replaced by the TRACE_IDX_AUTO_FILTER filter.

- The system-defined preference CTXSYS.INSO_FILTER has been replaced by the CTXSYS.AUTO_FILTER preference.

- The default values of DEFAULT_FILTER_FILE and DEFAULT_FILTER_BINARY system parameters has been changed from CTXSYS.INSO_FILTER to CTXSYS.AUTO_FILTER for new installations and databases upgrading to this release, if these default values have not been modified. For databases upgrading to this release which have modified these default values, the modified default values will continue to be used.

For backward compatibility, INSO_FILTER, as well as most of its associated filter types, constants, and attributes have been retained in this release; however, developers of Text applications should use AUTO_FILTER in new applications and update their older applications whenever possible.

About Migrating to the AUTO_FILTER Filter Type

Most applications will not have to be modified to reflect the change to the AUTO_FILTER type. The following migration steps will be performed automatically when you upgrade to this release:

- If an existing index uses the INSO_FILTER filter type, then it will be migrated to the AUTO_FILTER filter type.

- If an existing index uses the MAIL_FILTER filter type, then the INSO_TIMEOUT and INSO_OUTPUT_FORMATTING attributes will be migrated to the AUTO_FILTER_TIMEOUT and AUTO_FILTER_OUTPUT_FORMATTING attributes, respectively.

- If the default values of the system parameters DEFAULT_FILTER_FILE and DEFAULT_FILTER_BINARY have not already been modified, then they will be migrated from CTXSYS.INSO_FILTER to CTXSYS.AUTO_FILTER.

Although no actions are required to migrate to the AUTO_FILTER filter system, Oracle Text users upgrading their databases to this release should take the following steps to migrate away from using APIs deprecated by this release:

- If an index uses the MAIL_FILTER filter type with a nondefault mail configuration file, edit the file, replacing all occurrences of the INSOFILTER directive with the AUTO_FILTER directive.

- Replace the use of the PL/SQL constant TRACE_IDX_INSO_FILTER in your application with the TRACE_IDX_AUTO_FILTER constant.

- Replace the use of the system-defined preference CTXSYS.INSO_FILTER in your applications with CTXSYS.AUTO_FILTER.

CONTEXT Query Application

This appendix describes how to build a simple Web search application using the CONTEXT index type. The following topics are covered:

- Web Query Application Overview

- The PL/SQL Server Pages (PSP) Web Application

- The Java Server Pages (JSP) Web Application

Web Query Application Overview

A common use of Oracle Text is to index HTML files on Web sites and provide search capabilities to users. The sample application in this appendix indexes a set of HTML files stored in the database and uses a Web server connected to Oracle Database to provide the search service.

This appendix describes two versions of the Web query application:

- One using PL/SQL Server Pages (PSP)

- One using Java Server Pages (JSP)

Figure A-1 shows what the JSP version of the text query application looks like.

Figure A-1 The Text Query Application

Figure A-2 shows the results of the text query.

Figure A-2 The Text Query Application with Results

The application returns links to documents containing the search term. Each document has four links:

- The HTML link displays the document.
Graphics are not displayed in the filtered document. (You can see the source document for the first hit by looking at Figure 5-1.)

- The Highlight link displays the document with the search term highlighted. Figure 5-2 shows an example of highlighting.

- The Theme link shows the top 50 themes associated with the document. Figure 5-3 shows an example of theme extraction.

- The Gist link displays a short summary of the document. Figure 5-4 shows an example of this gisting feature.

The PL/SQL Server Pages (PSP) Web Application

The PSP Web application is based on PL/SQL server pages. Figure A-3 illustrates how the browser calls the PSP-stored procedure on Oracle Database through a Web server.

This section contains the following topics:

- PSP Web Application Prerequisites

- Building the PSP Web Application

- PSP Web Application Sample Code

Figure A-3 The PSP Web Application

PSP Web Application Prerequisites

This application has the following requirements:

- Your Oracle Database must be up and running.

- The SCOTT account is unlocked with password tiger, and has CREATE, RESOURCE, and CTXAPP privileges. See Oracle Database SQLJ Developer's Guide for a connection example.

- You have the Oracle PL/SQL gateway running. See Oracle Database Development Guide for complete information about setting up the PL/SQL gateway and developing PL/SQL web applications.

- You have a Web server such as Apache up and running and correctly configured to send requests to Oracle Database. See Oracle Database 2 Day + PHP Developer's Guide for information about installing Apache HTTP Server.

Building the PSP Web Application

This section describes how to build the PSP Web application.

The following steps describe the process for creating the PSP Web application:

1. Create Your Text Tables

You must create text tables with the CREATE TABLE command to store your HTML files. These examples create the tables output_table, gist_table, and theme_table as follows:

CREATE TABLE output_table  (query_id NUMBER, document CLOB);
CREATE TABLE gist_table  (query_id NUMBER, pov VARCHAR2(80), gist CLOB);
CREATE TABLE theme_table  (query_id NUMBER, theme VARCHAR2(2000), weight NUMBER);

2. Load HTML Documents into Table Using SQL*Loader

You must load the text tables with the HTML files. This example uses the control file loader.ctl to load the files named in loader.dat. The SQL*Loader statement is as follows:

% sqlldr userid=scott/tiger control=loader.ctl

3. Create the CONTEXT Index

Index the HTML files by creating a CONTEXT index on the text column as shown here. Because you are indexing HTML, this example uses the NULL_FILTER preference type for no filtering and uses the HTML_SECTION_GROUP type as follows:

create index idx_search_table on search_table(text)
indextype is ctxsys.context parameters
('filter ctxsys.null_filter section group CTXSYS.HTML_SECTION_GROUP');

4. Compile the search_htmlservices Package in Oracle Database

The application must present selected documents to the user. To do so, Oracle Database must read the documents from the CLOB in search_table and output the result for viewing, This is done by calling procedures in the search_htmlservices package. The file search_htmlservices.sql must be compiled. You can do this at the SQL*Plus prompt as follows:

SQL> @search_htmlservices.sql

Package created.

5. Compile the search_html PSP Page with loadpsp

The search page is invoked by calling search_html.psp from a browser. You compile search_html in Oracle Database with the loadpsp command-line program as follows:

% loadpsp -replace -user scott/tiger search_html.psp

The output will appear as:

"search_html.psp": procedure "search_html" created.

See Also:

Oracle Database Development Guide for more information about using PSP

6. Configure Your Web Server

You must configure your Web server to accept client PSP requests as a URL. Your Web server forwards these requests to Oracle Database and returns server output to the browser. See Figure A-3.

You can use the Oracle WebDB Web listener or Oracle Application Server, which includes the Apache Web server. See Oracle Database 2 Day + PHP Developer's Guide for information about installing Apache HTTP Server.

7. Enter the Query from a Browser

You can access the query application from a browser using a URL. You configure the URL with your Web server. An example URL might look like:

http://server.example.com:7777/mypath/search_html

The application displays a query entry box in your browser and returns the query results as a list of HTML links, as shown in Figure A-1 and Figure A-2.

PSP Web Application Sample Code

This section lists the code used to build the example Web application. It includes the following files:

- loader.ctl

- loader.dat

- search_htmlservices.sql

- search_html.psp

loader.ctl

This example shows a sample loader.ctl file. It is used by sqlldr to load the data file, loader.dat.

LOAD DATA
INFILE 'loader.dat'
INTO TABLE search_table
REPLACE
FIELDS TERMINATED BY ';'
(tk             INTEGER,
title          CHAR,
text_file      FILLER CHAR,
text           LOBFILE(text_file) TERMINATED BY EOF)

loader.dat

This example shows a sample loader.dat file. Each row contains three fields: a reference number for the document, a label (or "title"), and the name of the HTML document to load into the text column of search_table. The file has been truncated for this example.

1;   Pizza Shredder;Pizza.html
2;   Refrigerator w/ Front-Door Auto Cantaloupe Dispenser;Cantaloupe.html
3;   Self-Tipping Couch;Couch.html
4;   Home Air Dirtier;Mess.html
5;   Set of Pet Magnets;Pet.html
6;   Esteem-Building Talking Pillow;Snooze.html

HTML Files for loader.dat Example

The HTML files that are named and loaded into loader.dat are included here for your reference as follows:

- Pizza.html

- Cantaloupe.html

- Couch.html

- Mess.html

- Pet.html

- Snooze.html

Pizza.html

<html>
<header>
<title>The Pizza Shredder</title>
</header>
<body>

<h2>The Pizza Shredder</h2>
<h4>Keeping your pizza preferences secure</h4>

So it's the end of a long evening. Beer has been drunk, pizza has been eaten.
<p>
But there's left-over pizza - what are you going to do with it?

<p>
You could save it for the morning, or you could feed it to your pet.  But if neither of those appeal (maybe you don't have a pet?) then you'll be throwing it in the trash.

<p>
But wait a minute - anybody could look through your trash, and figure out what kind of pizza you've been eating! "No big deal", I hear you say. But it is! Once they've figured out that your favourite pizza is pepperoni flavour, then it's only a short step to figuring out that your top-secret online banking password is "pepperoni_pizza".

<p>
Get one over the dumpster-divers with our new patent-pending "Mk III Pizza Shredder".  Cross-cut blades ensure your pizza will be rendered unreadable, nobody will be able to identify the original toppings. Also doubles as a lettuce-shredder and may also be used for removing unwanted finger-tips.

<h2>Model Comparison</h2>

<table border="1">
<tr><th>Model</th><th>Blades0</th><th>Pizza Thickness</th><th>Price</th></tr>
<tr><td>Mk I</td><td>Plastic</td><td>1/2 inch (Thin Crust)</td><td>$69.99</td></tr>
<tr><td>Mk II</td><td>Brass</td><td>1 inch (Deep Pan)</td><td>$99.99</td></tr>
<tr><td>Mk III</td><td>Carbon Steel</td><td>2 inch (Calzoni)</td><td>$129.99</td></tr>
</table>

</body>
</html>

Cantaloupe.html

<html>
<header>
<title>The Fridge with a Cantaloupe Dispenser</title>
</header>
<body>
<h2>The Fridge with a Cantaloupe Dispenser</h2>
<h4>A nice cold melon at the touch of a button</h4>

Does your refrigerator only have a boring water dispenser in the door?

<p>
When you're hungry for a cantaloupe, do you have to expend valuable energy opening the fridge door and fishing around amongst the half-used packets of pet food?

<p>
Do your friends complain that they wish there was an effortless way to get cantaloupes from your fridge? Do you overhear them saying they're tired of always having to rummage through your moldy leftovers and seal-a-meals to get to the cold melons?

<p>
What you need is the convenience of a built-in cantaloupe dispenser.

<p>
Impress your friends. Win praise from your neighbors. Become a legendary host!

<p>
<b>Try our new <i>Melonic 2000</i> model!</b>

<p>
Works with honeydews and small crenshaws too.

<p>
Let the <i>Melonic 2000</i> go to work for you. Order one now at your local <i>Seers & Rowbucks</i>.

</body>
</html>

Couch.html

<html>
<header>
<title>The Self-Tipping Couch</title>
</header>
<body>
<h2>The Self-Tipping Couch</h2>

<h4>Sometimes it's hard work to get off the couch</h4>

<p>
Sometimes it's hard work to get your partner, or your pet, off the couch.

<p>
The <b>Self-Tipping Couch</b> solves these problems for you. At the touch of a button it will deposit the contents of the couch onto the floor in front of it.

<p>
The <b>Self-Tipping Couch</b> has been proven to boost communication with stubborn spouses, children, and relatives.

<p>
You will never again need to yell, "Get off the couch!" Simply press a button whenever you desire and all those couch hoggers are gently dumped onto your carpet.

<p>
Get your own <b>Self-Tipping Couch</b> TODAY!

</body>
</html>

Mess.html

<html>
<header>
<title>Home Air Dirtier</title>
</header>
<body>
<h2>Home Air Dirtier</h2>
<h4>Missing your home in the middle of the city?</h4>

<p>
Like many ex-city-dwellers, you might be finding that the air in the countryside is just too clean.

<p>
You can remedy this right now with the <i>UltraAppliance</i> <b>Home Air Dirtier</b>.

<p>
Simply insert our patented <i>CityFilth</i> cartridge, and soon you'll be enjoying the aromas of vehicle fumes and decaying garbage that you're used to from home.

<p>
<b>Please note:</b> Decaying garbage smells may confuse your pet. No matter how much he hunts, he will not be able to find the garbage he can smell.
We recommend adding genuine garbage to your environment if this is a concern.

</body>
</html>

Pet.html

<html>
<header>
<title>The Pet Magnet</title>
</header>
<body>
<h2>The Pet Magnet</h2>

<h4>Every pet owner loves to let his or her pet run free, but that's not always possible</h4>

<p>
Sometimes local laws require pets to be on leashes. Sometimes a free-roaming pet will ruin a flower bed, leave a "calling card" on the sidewalk, or chew through another pet. In the case of extremely smart pets, like chimpanzees or dolphins, the unattended pet may get away and run up hundreds of dollars worth of long-distance charges on your phone.

<p>
But leashes aren't always a practical answer. They can be too confining, or too big, or can tug uncomfortably at the pet's neck. They may get tangled, or wrapped around poles or passersby. Pets may chew through the leash, or, again, in the case of extremely smart pets, burn through it with an acetylene torch. In the case of cats, leashes simply look ridiculous, as though the pet owner really wanted to own a dog but got confused at the pet store.

<p>
<img align="right" src="http://141.144.14.148:8080/dog_magnet.png">

The <b>Hold 'Em 2000 Pet Magnet</b> from <i>UltraAppliance</i> is the answer. Instead of old-fashioned leashes, the <b>Hold 'Em 2000 Pet Magnet</b> keeps your pet under control in a humane and simple way.

<p>
Here's how it works. Dozens of small magnets are placed underneath the coat of your pet, where they remain painlessly invisible. Any time you need to recall your animal, you merely activate the handy, massive Hold 'Em 2000 Pet Magnet electromagnet (fits inside any extremely oversized purse) and your pet is gently and painlessly dragged to you from up to 100 yards. It's a must-have for any pet owner!

<p>

<blockquote>
<i>
"The <b>Hold 'Em 2000 Pet Magnet</b> not only keeps my dog from running away, but the electromagnet also comes in very handy if I need to find a needle in a haystack"</i>
-- Anonymous Celebrity (hint: Hotel Chain Heiress)
</blockquote>
</body>
</html>

Figure A-4 dog_magnet.png image referenced in Pet.html

Snooze.html

<html>
<header>
<title>Esteem-building Talking Pillow</title>
</header>
<body>
<h2>Esteem-building Talking Pillow</h2>
<h4>Do you feel less than your true potential when you wake up in the morning?</h4>

<p>
We searched for a way to capture the wasted time spent sleeping and to use this precious time to build motivation, character, and self esteem.

<p>
We are proud to announce the <b>Esteem-building Talking Pillow</b>. Our pride in this wonderful invention glows even more because: <i>We use our own invention every night!</i>

<p>
Only you will know that you are sleeping with the <b>Esteem-building Talking Pillow</b> because only you can hear the soothing affirmations that gently enter your brain through the discreet speaker.

<p>
You will wake up refreshed and raring to go with a new sense of pride and enthusiasm for any task the day may bring.

<p>
Be the first to own the <b>Esteem-building Talking Pillow</b>! Your friends and fellow workers will be amazed when you no longer cower in the corner. Now you will join in every conversation.

<p>
<b>Disclaimer:</b> Not responsible for narcissism and hyberbolic statements. May cause manic behavior with overuse.

</body>
</html>

search_htmlservices.sql

set define off

create or replace package search_htmlServices as
procedure showHTMLDoc (p_id in numeric);
procedure showDoc  (p_id in varchar2, p_query in varchar2);
end search_htmlServices;
/
show errors;

create or replace package body search_htmlServices as

procedure showHTMLDoc (p_id in numeric) is
v_clob_selected   CLOB;
v_read_amount     integer;
v_read_offset     integer;
v_buffer          varchar2(32767);
begin

select text into v_clob_selected from search_table where tk = p_id;
v_read_amount := 32767;
v_read_offset := 1;
begin
loop
dbms_lob.read(v_clob_selected,v_read_amount,v_read_offset,v_buffer);
htp.print(v_buffer);
v_read_offset := v_read_offset + v_read_amount;
v_read_amount := 32767;
end loop;
exception
when no_data_found then
null;
end;
end showHTMLDoc;

procedure showDoc (p_id in varchar2, p_query in varchar2) is

v_clob_selected   CLOB;
v_read_amount     integer;
v_read_offset     integer;
v_buffer          varchar2(32767);
v_query           varchar(2000);
v_cursor          integer;

begin
htp.p('<html><title>HTML version with highlighted terms</title>');
htp.p('<body bgcolor="#ffffff">');
htp.p('<b>HTML version with highlighted terms</b>');

begin
ctx_doc.markup (index_name => 'idx_search_table',
textkey    => p_id,
text_query => p_query,
restab     => v_clob_selected,
starttag   => '<i><font color=red>',
endtag     => '</font></i>');

v_read_amount := 32767;
v_read_offset := 1;
begin
loop
dbms_lob.read(v_clob_selected,v_read_amount,v_read_offset,v_buffer);
htp.print(v_buffer);
v_read_offset := v_read_offset + v_read_amount;
v_read_amount := 32767;
end loop;
exception
when no_data_found then
null;
end;

exception
when others then
null; --showHTMLdoc(p_id);
end;
end showDoc;
end search_htmlServices;
/
show errors

set define on

search_html.psp

<%@ plsql procedure="search_html" %>
<%@ plsql parameter="query" default="null" %>
<%! v_results number := 0; %>

<html>
<head>
<title>search_html Search </title>
</head>
<body>

<%

IF query IS NULL THEN
%>

<center>
<form method="post" action="search_html">
<b>Search for: </b>
<input type="text" name="query" size="30">&nbsp;
<input type="submit" value="Search">
</center>
<hr>

<%
ELSE
%>

<p>
<%!
color varchar2(6) := 'ffffff';
%>

<center>
<form method="post" action="search_html">
<b>Search for:</b>
<input type="text" name="query" size="30" value="<%= query %>">
<input type="submit" value="Search">
</form>
</center>
<hr>
<p>

<%
-- select statement
FOR DOC IN (
SELECT /*+ DOMAIN_INDEX_SORT */ rowid, tk, title, score(1) scr
FROM search_table
WHERE CONTAINS(text, query,1) >0
ORDER BY score(1) DESC
)
LOOP
v_results := v_results + 1;
IF v_results = 1 THEN

%>

<center>
<table border="0">
<tr bgcolor="#6699CC">
<th>Score</th>
<th>Title</th>
</tr>

<%      END IF; %>
<tr bgcolor="#<%= color %>">
<td> <%= doc.scr %>% </td>
<td> <%= doc.title %>
[<a href="search_htmlServices.showHTMLDoc?p_id=
<%= doc.tk %>">HTML</a>]
[<a href="search_htmlServices.showDoc?p_id=
<%= doc.tk %>&p_query=<%= query %>">Highlight</a>]
</td>
</tr>

<%
IF (color = 'ffffff') THEN
color := 'eeeeee';
ELSE
color := 'ffffff';
END IF;

END LOOP;
%>

</table>
</center>

<%
END IF;
%>
</body>
</html>

The Java Server Pages (JSP) Web Application

Creating the JSP-based Web application involves most of the same steps as those used in building the PSP-based application. See "Building the PSP Web Application" for more information. You can use the same loader.dat and loader.ctl files. However, with the JSP-based application, you do not need to do the following:

- Compile the search_htmlservices package

- Compile the search_html PSP page with loadpsp

This section contains the following topics:

- JSP Web Application Prerequisites

- JSP Web Application Sample Code

JSP Web Application Prerequisites

The JSP Web application has the following requirements:

- Your Oracle database is up and running.

- You have a Web server such as Apache Tomcat, which is capable of running JSP scripts that connect to the Oracle database using JDBC. You can also see Oracle Database 2 Day + PHP Developer's Guide for information about installing Apache HTTP Server.

JSP Web Application Sample Code

This section lists the Java code used to build the example Web application, as shown in the TextSearchApp.jsp file.

<%@page language="java" pageEncoding="utf-8" contentType="text/html; charset=utf-8" %>
<%@ page import="java.sql.*, java.util.*, java.net.*,
oracle.jdbc.*, oracle.sql.*, oracle.jsp.dbutil.*" %>

<%
// Change these details to suit your database and user details

String connStr = "jdbc:oracle:thin:@//servername:1521/pdb1";
String dbUser  = "scott";
String dbPass  = "tiger";

// The table we're running queries against is called SEARCH_TABLE.
// It must have columns:
//  tk     number  primary key,     (primary key is important for document services)
//  title  varchar2(2000),
//  text   clob
// There must be a CONTEXT index called IDX_SEARCH_TABLE on the text column

request.setCharacterEncoding("UTF-8");

java.util.Properties info=new java.util.Properties();
Connection conn  = null;
ResultSet rset   = null;
OracleCallableStatement callStmt = null;
Statement stmt   = null;
String userQuery = null;
String myQuery   = null;
String action    = null;
String theTk     = null;
URLEncoder myEncoder;
int count=0;
int loopNum=0;
int startNum=0;

userQuery     =   request.getParameter("query");
action        =   request.getParameter("action");
theTk         =   request.getParameter("tk");

if (action == null)  action = "";

// Connect to database

try {
DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver() );
info.put ("user",     dbUser);
info.put ("password", dbPass);
conn      = DriverManager.getConnection(connStr,info);
}
catch (SQLException e) {
%>    <b>Error: </b> <%= e %><p>  <%
}

if ( action.equals("doHTML") ) {
// Directly display the text of the document
try {

// not attempting to share the output table for this example, we'll truncate it each time
conn.createStatement().execute("truncate table OUTPUT_TABLE");

String sql = "{ call ctx_doc.filter( index_name=>'IDX_SEARCH_TABLE', textkey=> '" + theTk + "', restab=>'OUTPUT_TABLE', plaintext=>false ) }";
PreparedStatement s = conn.prepareCall( sql );
s.execute();

sql = "select document from output_table where rownum = 1";
stmt = conn.createStatement();
rset = stmt.executeQuery(sql);

rset.next();
oracle.sql.CLOB res = (oracle.sql.CLOB) rset.getClob(1);
// should fetch from clob piecewise, but to keep it simple we'll just fetch 32K to a string
String txt = res.getSubString(1, 32767);
out.println(txt);
}
catch (SQLException e) {
%>    <b>Error: </b> <%= e %><p> <%
}
}
else if ( action.equals("doHighlight") ) {
// Display the text of the document with highlighting from the "markup" function
try {

// not attempting to share the output table for this example, we'll truncate it each time
conn.createStatement().execute("truncate table OUTPUT_TABLE");

String sql = "{ call ctx_doc.markup( index_name=>'IDX_SEARCH_TABLE', textkey=> '" + theTk + "', text_query => '" + userQuery + "', restab=>'OUTPUT_TABLE', plaintext=>false, starttag => '<i><font color=\"red\">', endtag => '</font></i>' ) }";
PreparedStatement s = conn.prepareCall( sql );
s.execute();

sql = "select document from output_table where rownum = 1";
stmt = conn.createStatement();
rset = stmt.executeQuery(sql);

rset.next();
oracle.sql.CLOB res = (oracle.sql.CLOB) rset.getClob(1);
// should fetch from clob piecewise, but to keep it simple we'll just fetch 32K to a string
String txt = res.getSubString(1, 32767);
out.println(txt);
}
catch (SQLException e) {
%>    <b>Error: </b> <%= e %><p> <%
}
}

else if ( action.equals("doThemes") ) {
// Display the text of the document with highlighting from the "markup" function
try {

// not attempting to share the output table for this example, we'll truncate it each time
conn.createStatement().execute("truncate table THEME_TABLE");

String sql = "{ call ctx_doc.themes( index_name=>'IDX_SEARCH_TABLE', textkey=> '" + theTk + "', restab=>'THEME_TABLE') }";
PreparedStatement s = conn.prepareCall( sql );
s.execute();

sql = "select * from ( select theme, weight from theme_table order by weight desc ) where rownum <= 20";
stmt = conn.createStatement();
rset = stmt.executeQuery(sql);
int    weight = 0;
String theme  = "";
%>
<h2>The top 20 themes of the document</h2>
<table BORDER=1 CELLSPACING=0 CELLPADDING=0"
<tr bgcolor="#CCCC99">
<th><font face="arial" color="#336699">Theme</th>
<th><font face="arial" color="#336699">Weight</th>
</tr>
<%
while ( rset.next() ) {

theme  = rset.getString(1);
weight = (int)rset.getInt(2);
%>
<tr bgcolor="ffffe0">
<td align="center"><font face="arial"><b> <%= theme  %> </b></font></td>
<td align="center"><font face="arial"> <%= weight %></font></td>
</tr>
<%
}

%>
</table>
<%
}
catch (SQLException e) {
%>    <b>Error: </b> <%= e %><p> <%
}
}
else if ( action.equals("doGists") ) {
// Display the text of the document with highlighting from the "markup" function
try {

// not attempting to share the output table for this example, we'll truncate it each time
conn.createStatement().execute("truncate table GIST_TABLE");

String sql = "{ call ctx_doc.gist( index_name=>'IDX_SEARCH_TABLE', textkey=> '" + theTk + "', restab=>'GIST_TABLE', query_id=>1) }";
PreparedStatement s = conn.prepareCall( sql );
s.execute();

sql = "select pov, gist from gist_table where pov = 'GENERIC' and query_id = 1";
stmt = conn.createStatement();
rset = stmt.executeQuery(sql);
String pov   = "";
String gist  = "";

while ( rset.next() ) {

pov   = rset.getString(1);
oracle.sql.CLOB gistClob = (oracle.sql.CLOB) rset.getClob(2);

out.println("<h3>Document Gist for Point of View: " + pov + "</h3>");
gist = gistClob.getSubString(1, 32767);
out.println(gist);

}

%>
</table>
<%
}
catch (SQLException e) {
%>    <b>Error: </b> <%= e %><p> <%
}
}

if ( (action.equals("")) && ( (userQuery == null) || (userQuery.length() == 0) ) ) {
%>
<html>
<title>Text Search</title>
<body>
<table width="100%">
<tr bgcolor="#336699">
<td><font face="arial" align="left"
color="#CCCC99" size="+2">Text Search</td>
</tr>
</table>
<center>
<form method = post>
Search for:
<input type="text" name="query" size = "30">
<input type="submit" value="Search">
</form>
</center>
</body>
</html>
<%
}
else if (action.equals("") ) {
%>
<html>
<title>Text Search Result Page</title>
<body text="#000000" bgcolor="#FFFFFF" link="#663300"
vlink="#996633" alink="#ff6600">
<table width="100%">
<tr bgcolor="#336699">
<td><font face="arial" align="left"
color="#CCCC99" size=+2>Text Search</td>
</tr>
</table>
<center>
<form method = post action="TextSearchApp.jsp">
Search for:
<input type=text name="query" value="<%= userQuery %>" size = 30>
<input type=submit value="Search">
</form>
</center>
<%
myQuery   =   URLEncoder.encode(userQuery);
try {

stmt      = conn.createStatement();

String numStr =   request.getParameter("sn");
if(numStr!=null)
startNum=Integer.parseInt(numStr);
String theQuery =   translate(userQuery);

callStmt =(OracleCallableStatement)conn.prepareCall("begin "+
"?:=ctx_query.count_hits(index_name=>'IDX_SEARCH_TABLE', "+
"text_query=>?"+
"); " +
"end; ");
callStmt.setString(2,theQuery);
callStmt.registerOutParameter(1, OracleTypes.NUMBER);
callStmt.execute();
count=((OracleCallableStatement)callStmt).getNUMBER(1).intValue();
if(count>=(startNum+20)){
%>
<font color="#336699" FACE="Arial" SIZE=+1>Results
<%=startNum+1%> - <%=startNum+20%> of <%=count%> matches
<%
}
else if(count>0){
%>
<font color="#336699" FACE="Arial" SIZE=+1>Results
<%=startNum+1%> - <%=count%> of <%=count%> matches
<%
}
else {
%>
<font color="#336699" FACE="Arial" SIZE=+1>No match found
<%
}
%>
<table width="100%">
<TR ALIGN="RIGHT">
<%
if((startNum>0)&(count<=startNum+20))
{
%>
<TD ALIGN="RIGHT">
<a href="TextSearchApp.jsp?sn=<%=startNum-20 %>&query=
<%=myQuery %>">previous20</a>
</TD>
<%
}
else if((count>startNum+20)&(startNum==0))
{
%>
<TD ALIGN="RIGHT">
<a href="TextSearchApp.jsp?sn=<%=startNum+20
%>&query=<%=myQuery %>">next20</a>
</TD>
<%
}
else if((count>startNum+20)&(startNum>0))
{
%>
<TD ALIGN="RIGHT">
<a href="TextSearchApp.jsp?sn=<%=startNum-20 %>&query=
<%=myQuery %>">previous20</a>
<a href="TextSearchApp.jsp?sn=<%=startNum+20 %>&query=
<%=myQuery %>">next20</a>
</TD>
<%
}
%>
</TR>
</table>
<%
String ctxQuery =
" select /*+ FIRST_ROWS */ " +
"   tk, TITLE, score(1) scr, " +
"   ctx_doc.snippet ('IDX_SEARCH_TABLE', tk, '" + theQuery + "') " +
" from search_table " +
" where contains(TEXT, '"+theQuery+"',1 ) > 0 " +
" order by score(1) desc";
rset = stmt.executeQuery(ctxQuery);
String   tk           = null;
String[] colToDisplay = new String[1];
int      myScore      = 0;
String   snippet      = "";
int      items        = 0;
while (rset.next()&&items< 20) {
if(loopNum>=startNum)
{
tk = rset.getString(1);
colToDisplay[0] = rset.getString(2);
myScore         = (int)rset.getInt(3);
snippet         = rset.getString(4);
items++;
if (items == 1) {
%>
<center>
<table BORDER=1 CELLSPACING=0 CELLPADDING=0 width="100%"
<tr bgcolor="#CCCC99">
<th><font face="arial" color="#336699">Score</th>
<th><font face="arial" color="#336699">TITLE</th>
<th><font face="arial" color="#336699">Snippet</th>
<th> <font face="arial"
color="#336699">Document Services</th>
</tr>
<%   } %>
<tr bgcolor="#FFFFE0">
<td ALIGN="CENTER"> <%= myScore %>%</td>
<td> <%= colToDisplay[0] %> </td>
<td> <%= snippet %> </td>
<td>
<a href="TextSearchApp.jsp?action=doHTML&tk=<%= tk %>">HTML</a> &nbsp;
<a href="TextSearchApp.jsp?action=doHighlight&tk=<%= tk %>&query=<%= theQuery %>">Highlight</a> &nbsp;
<a href="TextSearchApp.jsp?action=doThemes&tk=<%= tk %>&query=<%= theQuery %>">Themes</a> &nbsp;
<a href="TextSearchApp.jsp?action=doGists&tk=<%= tk %>">Gist</a> &nbsp;
</td>
</tr>
<%
}
loopNum++;
}
} catch (SQLException e) {
%>
<b>Error: </b> <%= e %><p>
<%
} finally {
if (conn != null) conn.close();
if (stmt != null) stmt.close();
if (rset != null) rset.close();
}
%>
</table>
</center>
<table width="100%">
<TR ALIGN="RIGHT">
<%
if((startNum>0)&(count<=startNum+20))
{
%>
<TD ALIGN="RIGHT">
<a href="TextSearchApp.jsp?sn=<%=startNum-20 %>&query=
<%=myQuery %>">previous20</a>
</TD>
<%
}
else if((count>startNum+20)&(startNum==0))
{
%>
<TD ALIGN="RIGHT">
<a href="TextSearchApp.jsp?sn=<%=startNum+20 %>&query=
<%=myQuery %>">next20</a>
</TD>
<%
}
else if((count>startNum+20)&(startNum>0))
{
%>
<TD ALIGN="RIGHT">
<a href="TextSearchApp.jsp?sn=<%=startNum-20 %>&query=
<%=myQuery %>">previous20</a>
<a href="TextSearchApp.jsp?sn=<%=startNum+20 %>&query=
<%=myQuery %>">next20</a>
</TD>
<%
}
%>
</TR>
</table>
</body></html>
<%}

%>
<%!
public String translate (String input)
{
Vector reqWords = new Vector();
StringTokenizer st = new StringTokenizer(input, " '", true);
while (st.hasMoreTokens())
{
String token = st.nextToken();
if (token.equals("'"))
{
String phrase = getQuotedPhrase(st);
if (phrase != null)
{
reqWords.addElement(phrase);
}
}
else if (!token.equals(" "))
{
reqWords.addElement(token);
}
}
return getQueryString(reqWords);
}

private String getQuotedPhrase(StringTokenizer st)
{
StringBuffer phrase = new StringBuffer();
String token = null;
while (st.hasMoreTokens() && (!(token = st.nextToken()).equals("'")))
{
phrase.append(token);
}
return phrase.toString();
}

private String getQueryString(Vector reqWords)
{
StringBuffer query = new StringBuffer("");
int length = (reqWords == null) ? 0 : reqWords.size();
for (int ii=0; ii < length; ii++)
{
if (ii != 0)
{
query.append(" & ");
}
query.append("{");
query.append(reqWords.elementAt(ii));
query.append("}");
}
return query.toString();
}
%>

CATSEARCH Query Application

This appendix describes how to build a simple Web-search application using the CATSEARCH index type.

The following topics are covered:

- CATSEARCH Web Query Application Overview

- The JSP Web Application

CATSEARCH Web Query Application Overview

The CTXCAT index type is well suited for merchandise catalogs that have short descriptive text fragments and associated structured data. This appendix describes how to build a browser-based bookstore catalog that users can search to find titles and prices.

This application is written in Java Server Pages (JSP).

The JSP Web Application

This application is based on Java Server pages (JSP) and has the following requirements:

- Your Oracle database is up and running.

- You have a Web server such as Apache Tomcat, which is capable of running JSP scripts that connect to the Oracle database using JDBC. You can also see Oracle Database 2 Day + PHP Developer's Guide for information about installing Apache HTTP Server.

This section contains the following topics:

- Building the JSP Web Application

- JSP Web Application Sample Code

Building the JSP Web Application

This application models an online bookstore where you can look up book titles and prices.

The following steps describe the process for creating the JSP Web application:

1. Create Your Table

You must create the table to store book information such as title, publisher, and price. From SQL*Plus:

sqlplus>create table book_catalog (
id        numeric,
title     varchar2(80),
publisher varchar2(25),
price     numeric )

2. Load data using SQL*Loader

Load the book data from the operating system command-line with SQL*Loader:

% sqlldr userid=ctxdemo/ctxdemo control=loader.ctl

3. Create the index set

You can create the index set from SQL*Plus:

sqlplus>begin
ctx_ddl.create_index_set('bookset');
ctx_ddl.add_index('bookset','price');
ctx_ddl.add_index('bookset','publisher');
end;
/

4. Create the CTXCAT index

You can create the CTXCAT index from SQL*Plus as follows:

sqlplus>create index book_idx on book_catalog (title)
indextype is ctxsys.ctxcat
parameters('index set bookset');

5. Try a simple search using CATSEARCH

You can test the newly created index in SQL*Plus as follows:

sqlplus>select id, title from book_catalog
where catsearch(title,'Java','price > 10 order by price') > 0

6. Copy the catalogSearch.jsp file to your Web site JSP directory

When you do so, you can access the application from a browser. The URL should be http://localhost:port/path/catalogSearch.jsp

The application displays a query entry box in your browser and returns the query results as a list of HTML links. See Figure B-1.

Figure B-1 Screen shot of Web Query Application

JSP Web Application Sample Code

This section lists the code used to build the example Web application. It includes the following files:

- loader.ctl

- loader.dat

- catalogSearch.jsp

See Also:

http://www.oracle.com/technetwork/indexes/downloads/index.html

loader.ctl

LOAD DATA
INFILE 'loader.dat'
INTO TABLE book_catalog
REPLACE
FIELDS TERMINATED BY ';'
(id, title, publisher, price)

loader.dat

1; A History of Goats; SPINDRIFT BOOKS;50
2; Robust Recipes Inspired by Eating Too Much;SPINDRIFT BOOKS;28
3; Atlas of Greenland History; SPINDRIFT BOOKS; 35
4; Bed and Breakfast Guide to Greenland; SPINDRIFT BOOKS; 37
5; Quitting Your Job and Running Away; SPINDRIFT BOOKS;25
6; Best Noodle Shops of Omaha ;SPINDRIFT BOOKS; 28
7; Complete Book of Toes; SPINDRIFT BOOKS;16
8; Complete Idiot's Guide to Nuclear Technology;SPINDRIFT BOOKS; 28
9; Java Programming for Woodland Animals; LOW LIFE BOOK CO; 10
10; Emergency Surgery Tips and Tricks;SPOT-ON PUBLISHING;10
11; Programming with Your Eyes Shut; KLONDIKE BOOKS; 10
12; Forest Fires of North America, 1858-1882; CALAMITY BOOKS; 11
13; Spanish in Twelve Minutes; WRENCH BOOKS 11
14; Better Sex and Romance Through C++; CALAMITY BOOKS; 12
15; Oracle Internet Application Server Enterprise Edition; KANT BOOKS; 12
16; Oracle Internet Developer Suite; SPAMMUS BOOK CO;13
17; Telling the Truth to Your Pets; IBEX BOOKS INC; 13
18; Go Ask Alice's Restaurant;HUMMING BOOKS;    13
19; Life Begins at 93;  CALAMITY BOOKS;   17
20; Dating While Drunk;  BALLAST BOOKS;  14
21; The Second-to-Last Mohican; KLONDIKE BOOKS;  14
22; Eye of Horus; An Oracle of Ancient Egypt; BIG LITTLE BOOKS;     15
23; Introduction to Sitting Down; IBEX BOOKS INC;  15

catalogSearch.jsp

<%@ page import="java.sql.* , oracle.jsp.dbutil.*" %>
<jsp:useBean id="name" class="oracle.jsp.jml.JmlString" scope="request" >
<jsp:setProperty name="name" property="value" param="v_query" />
</jsp:useBean>

<%
String connStr="jdbc:oracle:thin:@machine-domain-name:1521:betadev";

java.util.Properties info = new java.util.Properties();

Connection conn = null;
ResultSet  rset = null;
Statement  stmt = null;

if (name.isEmpty() ) {

%>
<html>
<title>Catalog Search</title>
<body>
<center>
<form method=post>
Search for book title:
<input type=text name="v_query" size=10>
where publisher is
<select name="v_publisher">
<option value="ADDISON WESLEY">ADDISON WESLEY
<option value="HUMMING BOOKS">HUMMING BOOKS
<option value="WRENCH BOOKS">WRENCH BOOKS
<option value="SPOT-ON PUBLISHING">SPOT-ON PUBLISHING
<option value="SPINDRIFT BOOKS">SPINDRIFT BOOKS
<option value="LOW LIFE BOOK CO">LOW LIFE BOOK CO
<option value="KLONDIKE BOOKS">KLONDIKE BOOKS
<option value="CALAMITY BOOKS">CALAMITY BOOKS
<option value="IBEX BOOKS INC">IBEX BOOKS INC
<option value="BIG LITTLE BOOKS">BIG LITTLE BOOKS
</select>
and price is
<select name="v_op">
<option value="=">=
<option value="&lt;">&lt;
<option value="&gt;">&gt;
</select>
<input type=text name="v_price" size=2>
<input type=submit value="Search">
</form>
</center>
<hr>
</body>
</html>

<%
}
else {

String v_query = request.getParameter("v_query");
String v_publisher = request.getParameter("v_publisher");
String v_price = request.getParameter("v_price");
String v_op    = request.getParameter("v_op");
%>

<html>
<title>Catalog Search</title>
<body>
<center>
<form method=post action="catalogSearch.jsp">
Search for book title:
<input type=text name="v_query" value=
<%= v_query %>
size=10>
where publisher is
<select name="v_publisher">
<option value="ADDISON WESLEY">ADDISON WESLEY
<option value="HUMMING BOOKS">HUMMING BOOKS
<option value="WRENCH BOOKS">WRENCH BOOKS
<option value="SPOT-ON PUBLISHING">SPOT-ON PUBLISHING
<option value="SPINDRIFT BOOKS">SPINDRIFT BOOKS
<option value="LOW LIFE BOOK CO">LOW LIFE BOOK CO
<option value="KLONDIKE BOOKS">KLONDIKE BOOKS
<option value="CALAMITY BOOKS">CALAMITY BOOKS
<option value="IBEX BOOKS INC">IBEX BOOKS INC
<option value="BIG LITTLE BOOKS">BIG LITTLE BOOKS
</select>
and price is
<select name="v_op">
<option value="=">=
<option value="&lt;">&lt;
<option value="&gt;">&gt;
</select>
<input type=text name="v_price" value=
<%= v_price %> size=2>
<input type=submit value="Search">
</form>
</center>

<%
try {

DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver() );
info.put ("user", "ctxdemo");
info.put ("password","ctxdemo");
conn = DriverManager.getConnection(connStr,info);

stmt = conn.createStatement();
String theQuery = request.getParameter("v_query");
String thePrice = request.getParameter("v_price");

// select id,title
// from book_catalog
// where catsearch (title,'Java','price >10 order by price') > 0

// select title
// from book_catalog
// where catsearch(title,'Java','publisher = ''CALAMITY BOOKS''
and price < 40 order by price' )>0

String myQuery = "select title, publisher, price from book_catalog
where catsearch(title, '"+theQuery+"',
'publisher = ''"+v_publisher+"'' and price "+v_op+thePrice+"
order by price' ) > 0";
rset = stmt.executeQuery(myQuery);

String color = "ffffff";

String myTitle = null;
String myPublisher = null;
int myPrice = 0;
int items = 0;

while (rset.next()) {
myTitle     = (String)rset.getString(1);
myPublisher = (String)rset.getString(2);
myPrice     = (int)rset.getInt(3);
items++;

if (items == 1) {
%>
<center>
<table border="0">
<tr bgcolor="#6699CC">
<th>Title</th>
<th>Publisher</th>
<th>Price</th>
</tr>
<%
}
%>
<tr bgcolor="#<%= color %>">
<td> <%= myTitle %></td>
<td> <%= myPublisher %></td>
<td> $<%= myPrice %></td>
</tr>
<%
if (color.compareTo("ffffff") == 0)
color = "eeeeee";
else
color = "ffffff";

}

} catch (SQLException e) {

%>

<b>Error: </b> <%= e %><p>

<%

} finally {
if (conn != null) conn.close();
if (stmt != null) stmt.close();
if (rset != null) rset.close();
}

%>
</table>
</center>
</body>
</html>
<%
}
%>

Glossary

alternate spelling

In Oracle Text, alternate spelling refers specifically to the use of spelling variations in German, Swedish, and Dutch; these variations may be indexed if the BASIC_LEXER attribute ALTERNATE_SPELLING has been specified.

attribute

An attribute is an optional parameter associated with a preference. For example, the BASIC_LEXER preference includes the base_letter attribute, which can have either the value of YES (perform base-letter conversions) or NO (do not perform such conversions). Attributes are set with the CTX_DDL.SET_ATTRIBUTE procedure or with the ALTER INDEX statement. See also: preference, base-letter conversion.

attribute section

A user-defined section, representing an attribute of an XML document, such as AUTHOR or TITLE. Attribute sections are added to section groups with CTX_DDL.ADD_ATTR_SECTION or with the ALTER INDEX statement. See also: AUTO_SECTION_GROUP, section, XML_SECTION_GROUP.

AUTO_SECTION_GROUP

A section group used to automatically crate a zone section for each start-and end-tag pair in an XML document; attribute sections are automatically created for XML tags that have attributes. See also: attribute section, section, section group, XML_SECTION_GROUP, zone section.

base-letter conversion

The conversion of a letter with alternate forms (such as accents, umlauts, or cedillas) to its basic form (for example, without an accent).

BASIC_SECTION_GROUP

A section group used to define sections where the start and end tags are of the form <tag> and </tag>. It does not support non-basic tags, such as comment tags or those with attributes or unbalanced parentheses. See also: HTML_SECTION_GROUP, section, section group.

case

Case refers to the capitalization of a word or letter, where upper-case letters are capitals (M instead of m, for example). Not all languages have case. Mixed-case indexing is supported for some languages, notably those of Western Europe.

classification

Also known as document classification. The conceptual separation of source documents into groups, or clusters, based on their content. For example, a group of documents might be separated into clusters concerning medicine, finance, and sports.

Oracle Text includes rule-based classification, in which a person writes the rules for classifying documents (in the form of queries), and Oracle Text performs the document classification according to the rules; supervised classification, in which Oracle Text creates classification rules based on a set of sample documents; and clustering (also known as unsupervised classification), in which the clusters and rules are both created by Oracle Text.

clustering

Also known as unsupervised classification. See: classification.

composite domain index

Also known as CDI type of index. An Oracle Text index that not only indexes and processes a specified text column, but also indexes and processes FILTER BY and ORDER BY structured columns that are specified during index creation. See also: domain index.

CONTEXT index

The basic type of Oracle Text index; an index on a text column. A CONTEXT index is useful when your source text consists of many large, coherent documents. Applications making use of CONTEXT indexes use the CONTAINS query operator to retrieve text.

CTXAPP role

A role for application developers that enables a user to create Oracle Text indexes and index preferences, and to use PL/SQL packages. This role should be granted to Oracle Text users.

CTXCAT index

A combined index on a text column and one or more other columns. Typically used to index small documents or text fragments, such as item names, prices and descriptions typically found in catalogs. The CTXCAT index typically has better mixed-query performance than the CONTEXT index.

Applications query this index with the CATSEARCH operator. This index is transactional, which means that it automatically updates itself with DML to the base table.

CTXRULE index

A CTXRULE index is used to build a document classification application. The CTXRULE index is an index created on a table of queries, where the queries serve as rules to define the classification criteria. This index is queried with the MATCHES operator.

CTXSYS user

The CTXSYS user is created at install time. The CTXSYS user can view all indexes; sync all indexes; run ctxkbtc, the knowledge base extension compiler; query all system-defined views; and perform all the tasks of a user with the CTXAPP role.

datastore

In Oracle Text, datastore refers to the method of storing text. The method is determined by specifying a storage preference of a particular type. For example, the DIRECT_DATASTORE type stores data directly into the text column, while the URL_DATASTORE specifies that data is stored externally in a location specified by a URL.

domain index

An Oracle Database domain index that indexes and processes a specified text column. See also: composite domain index.

endjoin

One or more non-alphanumeric characters that, when encountered as the last character in a token, explicitly identify the end of the token. The characters, as well as any startjoin characters that immediately follow it, are included in the Text index entry for the token. For example, if ++ is specified as an endjoin, then C++ will be recognized and indexed as a single token. See also: printjoin, skipjoin, startjoin.

field section

A field section is similar to a zone section, with the main difference that the content between the start and end tags of a field section can be indexed separately from the rest of the document. This enables field section content to be "hidden" from a normal query. (The INPATH and WITHIN operators may be used to find the term in such a section.) Field sections are useful when there is a single occurrence of a section in a document, such as a field in a news header. Field sections are added to section groups with the CTX_DDL.ADD_FIELD_SECTION procedure or with the ALTER INDEX statement. See also: INPATH operator, section, WITHIN operator, zone section.

filtering

One of the steps in the Oracle Text index-creation process. Depending on the filtering preferences associated with the creation of the index, one of three things happens during filtering: Formatted documents are filtered into marked-up text; text is converted from a non-database character set to a database character set; or no filtering takes place (HTML, XML, and plain-text documents are not filtered).

fuzzy matching

A fuzzy-matching query is one in which the query is expanded to include words that are spelled similarly to the specified term. This type of expansion is helpful for finding more accurate results when there are frequent misspellings in a document set. Fuzzy matching is invoked with the FUZZY query operator.

HASPATH operator

A CONTAINS query operator used to find XML documents that contain a section path exactly as specified in the query. See also: PATH_SECTION_GROUP.

highlighting

Generically, in Oracle Text, highlighting refers to generating a version of a document, or document fragments, with query terms displayed or called out in a special way.

Specifically, there are three forms of highlighting. First, CTX_DOC.MARKUP returns a document with the query term surrounded by plaintext or HTML tags. Second, CTX_DOC.HIGHLIGHT returns offsets for the query terms, allowing the user to mark up the document as desired. Third, CTX_DOC.SNIPPET produces a concordance, with the query term displayed in fragments of surrounding text. markup.

HTML_SECTION_GROUP

A section group type used for defining sections in HTML documents. See also: BASIC_SECTION_GROUP, section, section group.

INPATH operator

A CONTAINS query operator used to search within tags, or paths, of an XML document. It enables more generic path denomination than the WITHIN operator. See also: WITHIN operator.

Key Word in Context (KWIC)

In Oracle Text, a presentation of a query term with the text that surrounds it in the source document. This presentation may consist of a single instance of the query term, several instances, or every instance in the source document. The CTX_DOC.SNIPPET procedure produces such a presentation. Also known as Key Word in Context (KWIC).

knowledge base

Oracle Text includes a knowledge base, which is a hierarchical tree of concepts used for theme indexing, ABOUT queries, and deriving themes for document services. You can create your own knowledge base or extend the standard Oracle Text knowledge base.

lexer

The Oracle Text lexer breaks source text into tokens—usually words—in accordance with a specified language. To extract tokens, the lexer uses parameters as defined by a lexer preference. These parameters include the definitions for the characters that separate tokens, such as whitespace, and whether to convert text to all uppercase or not. When theme indexing is enabled, the lexer analyses text to create theme tokens.

When an application needs to index a table containing documents in more than one language, it can utilize the MULTI_LEXER (the multilingual lexer) and create sub-lexers to handle each language. Each sub-lexer is added to the main multi-lexer with the CTX_DDl.ADD_SUB_LEXER procedure.

markup

A form of highlighting. The CTX_DOC.MARKUP and CTX_DOC.POLICY_MARKUP procedures take a query term and a document, and return the document with the query terms marked up; that is, surrounded either by plaintext characters or HTML tags. You can use predefined markup tags or specify your own. In comparison, CTX_DOC.HIGHLIGHT and CTX_DOC.POLICY_HIGHLIGHT return offsets for query terms, so you can add your own highlighting tags. See also: highlighting.

MDATA

See: metadata.

MDATA section

An MDATA section contains user-defined index metadata. Use of this metadata can speed up mixed CONTAINS queries. See also: metadata, mixed query, section.

metadata

Metadata is information about a document that is not part of a document's regular content. For example, if an HTML document contains <author>Mark Twain</author>, author is considered the metadata type and Mark Twain is considered the value for author.

Sections containing metadata, known as MDATA sections, can be added to a document with the CTX_DDL.ADD_MDATA_SECTION procedure. Taking advantage of metadata can speed up mixed queries. Such queries can be made with the MDATA operator. See also: mixed query, section.

mixed query

A query that searches for two different types of information; for example, text content and document type. For example, a search for Romeo and Juliet in <title> metadata is a mixed query.

name search

Name searching (also called name matching) provides a solution to match proper names that might differ in spelling due to orthographic variation. It also enables you to search for somewhat inaccurate data, such as might occur when a record's first name and surname are not properly segmented.

NEWS_SECTION_GROUP

A section group type used for defining sections in newsgroup-formatted documents as defined by RFC 1036. See also: section, section group.

normalized word

The form of a word after it has been transformed for indexing, according to transformational rules in effect. Depending on the rules in effect, the normalized form of a word may be the same as the form found in the source document. The normalized form of a word may also include both the original and transformed versions. For example, if New German Spelling has been specified, the word Potential is normalized to both Potenzial and Potential.

NULL_SECTION_GROUP

The default section group type when no sections are defined or when only SENTENCE or PARAGRAPH sections are defined. See also: section, section group, special section.

PATH_SECTION_GROUP

A section group type used for indexing XML documents. It is similar to the AUTO_SECTION_GROUP type, except that it enables the use of the HASPATH and INPATH operators. See also: AUTO_SECTION_GROUP, HASPATH operator, INPATH operator, section, section group.

preference

A preference is an optional parameter that affects the way Oracle Text creates an index. For example, a lexer preference specifies the lexer to use when processing documents, such as the JAPANESE_VGRAM_LEXER. There are preferences for storage, filtering, lexers, classifiers, wordlist, section types, and more. A preference may or may not have attributes associated with it. Preferences are set with the CTX_DDL.CREATE_PREFERENCE procedure. See also: attribute.

printjoin

One or more non-alphanumeric character that, when they appear anywhere in a word (beginning, middle, or end), are processed as alphanumeric and included with the token in an Oracle Text index. This includes printjoins that occur consecutively.

For example, if the hyphen (-) and underscore (_) characters are defined as printjoins, terms such as pseudo-intellectual and _file_ are stored in the Oracle Text index as pseudo-intellectual and _file_.

Printjoins differ from endjoins and startjoins in that position does not matter. For example, $35 will be indexed as one token if $ is defined as a startjoin or a printjoin, but as two tokens if it is an endjoin. See also: endjoin, printjoin, startjoin.

result set

A page of search results in applications can consist of many disparate elements — metadata of the first few documents, total hit counts, per-word hit counts, and so on. Generating these results in earlier versions of Oracle Text required several queries and calls. Each extra call takes time to reparse the query and look up index metadata. Additionally, some search operations, such as iterative query refinement or breakdown top ten, are difficult for SQL.

The result set interface enables you to produce the various kinds of data needed for a page of search results all at once, thus improving performance by sharing overhead. The result set interface can also return data views that are difficult to express in SQL.

rule-based classification

See: classification.

SDATA section

Structured/Sort Data section. Unlike the MDATA section type, which only supports equality searches, SDATA sections are designed to also support range searches. By default, all FILTER BY and ORDER BY columns are mapped as SDATA sections. An SDATA section contains user-defined index metadata. Use of this type of section can speed up mixed CONTAINS queries. See also: mixed query, section.

section

A section is a subdivision of a document; for example, everything within an <a>...</a> section of an HTML page.

Dividing a document into sections and then searching within sections enables you to narrow text queries down to blocks of text within documents. Section searching is useful when your documents have internal structure, such as HTML and XML documents. You can also search for text at the sentence and paragraph level.

Section searching is performed with the HASPATH, ISPATH, or WITHIN operator. Sections searching is enabled by the used of the section group when indexing.

The various section types include attribute, field, HTML, MDATA, special, stop, XML, and zone sections.

section group

A section group identifies a type of document set and implicitly indicate the tag structure for indexing. For instance, to index HTML tagged documents, you use the HTML_SECTION_GROUP. section group type. Likewise, to index XML tagged documents, you can use the XML_SECTION_GROUP section group type. Section groups are declared with the CTX_DDL.CREATE_SECTION_GROUP procedure or with the ALTER INDEX statement. See also: section.

skipjoin

A non-alphanumeric character that, when it appears within a word, identifies the word as a single token; however, the character is not stored with the token in the Text index. For example, if the hyphen character '-' is defined as a skipjoin, the word pseudo-intellectual is stored in the Text index as pseudointellectual. See also: endjoin, printjoin, startjoin.

startjoin

One or more non-alphanumeric characters that, when encountered as the first character in a token explicitly identify the start of the token. The characters, as well as any other startjoins characters that immediately follow it, are included in the Text index entry for the token. For example, if '$' is defined as a startjoin, then $35 is indexed as a single token. In addition, the first startjoins character in a string of startjoins characters implicitly ends the previous token. See also: endjoin, printjoin, skipjoin.

stemming

The expansion of a query term to include all terms having the same root word. For example, stemming the verb talk yields talking, talks, and talked, as well as talk (but not talkie). Stemming is distinct from wildcard expansion, in which results are related only through spelling, not through morphology. See also: wildcard expansion.

special section

A document section that is not bounded by tags. Instead, sections are formed by plaintext document structures such as sentences and paragraphs. Special sections are added to a section group with the CTX_DDL.ADD_SPECIAL_SECTION procedure. See also: section, section group.

stop section

A section that, when added to an AUTO_SECTION_GROUP, causes the information for document sections of that type to be ignored during indexing; the section content may still be searched, however. Stop sections are added to section groups with the CTX_DDL.ADD_STOP_SECTION procedure. See also: AUTO_SECTION_GROUP, section, section group.

stopclass

A class of tokens, such as NUMBERs, that are to be skipped over during indexing. Stopclasses are specified by adding them to stoplists with CTX_DDL.ADD_STOPCLASS. See also: stoplist.

stoplist

A list of words, known as stopwords, themes (stopthemes), and data classes (stopclasses) that are not to be indexed. By default, the system indexes text using the system-supplied stoplist that corresponds to a given database language.

Oracle Text provides default stoplists for most common languages including English, French, German, Spanish, Chinese, Dutch, and Danish. These default stoplists contain only stopwords. Stoplists are created with CTX_DDL.CREATE_STOPLIST or with the ALTER INDEX statement. See also: stopclass, stoptheme, stopword.

stoptheme

A theme to be skipped over during indexing. Stopthemes are specified by adding them to stoplists with CTX_DDL.ADD_STOPTHEMES. See also: stoplist.

stopword

A word to be skipped over during indexing. Stopwords are specified by adding them to stoplists with CTX_DDL.ADD_STOPWORD. They can also be dynamically added to an index using the ALTER INDEX statement. See also: stoplist.

sub-lexer

See: lexer.

supervised classification

See: classification.

theme

A topic associated with a given document. A document may have many themes. A theme does not have to appear in a document; for example, a document containing the words San Francisco may have California as one of its themes.

Theme components are added to indexes with the INDEX_THEMES attribute of the BASIC_LEXER preference; they may be extracted from a document with CTX_DOC.THEMES and queried with the ABOUT operator.

unsupervised classification

Also known as clustering. See: classification.

wildcard expansion

The expansion of a query term to return words that fit a given pattern. For example, expansion of the query term %rot% would return both trot and rotten. Wildcard expansion is distinct from stemming. See also: stemming.

whitespace

Characters that are treated as blank spaces between tokens. The predefined default values for whitespace are 'space' and 'tab'. The BASIC_LEXER uses whitespace characters (in conjunction with punctuations and newline characters) to identify character strings that serve as sentence delimiters for sentence and paragraph searching.

WITHIN operator

A CONTAINS query operator used to search for query terms within a given XML document section. It is similar to the INPATH operator, but less generic. See also: INPATH operator.

wordlist

An Oracle Text preference that enables features such as fuzzy, stemming, and prefix indexing for better wildcard searching, as well as substring and prefix indexing. The wordlist preference improves performance for wildcard queries with CONTAINS and CATSEARCH. Create wordlists with the CTX_DDL.ADD_WORDLIST procedure or with the ALTER INDEX statement. See also: preference.

XML section

A section that defined by XML tags, enabling XML section searching. Indexing with XML sections permits automatic sectioning as well as declaring document-type-sensitive sections. XML section searching includes attribute searching as well as path section searching with the INPATH, HASPATH, and WITHIN operators. See also: section.

XML_SECTION_GROUP

A section group used for identifying XML documents for indexing. See also: section, section group.

zone section

The basic type of document section; a body of text delimited by start and end tags in a document. Zone sections are well suited for defining sections in HTML and XML documents. Zone sections are added to section groups with the CTX_DDL.ADD_ZONE_SECTION procedure or with the ALTER INDEX statement. See also: field section, section, section group.

Index

A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Z

A

- ABOUT operator [1] , [2]

- ABOUT query

- adding for your language [1]

- case-sensitivity [1]

- definition [1]

- accents

- indexing characters with [1]

- ADD_SUB_LEXER procedure

- example [1]

- administration tool [1]

- all-at-once swap [1]

- ALTER INDEX statement

- rebuilding index [1]

- alternate_spelling attribute [1]

- alternate spelling [1]

- alternative grammar [1]

- alternative grammar template [1]

- alternative scoring [1]

- alternative scoring template [1]

- application

- sample [1] , [2]

- applications, updating [1]

- attribute

- searching XML [1]

- attribute sections [1]

- auction table schema example [1]

- AUTO_FILTER filter [1]

- AUTO_LEXER with fuzzy matching and stemming [1]

- AUTO keyword

- character sets and [1]

- AUTOMATIC keyword

- character sets and [1]

- automatic sections [1]

B

- background DML [1]

- base_letter attribute [1]

- base-letter conversion [1]

- BASIC_LEXER preference type [1]

- BFILE column

- indexing [1]

- BIG_IO index option [1]

- BINARY format column value [1]

- BLOB column

- indexing [1]

- blocking operations

- tuning queries with [1]

- b-tree index [1]

- bypassing rows [1]

C

- cantaloupe dispenser [1]

- case-insensitive queries [1]

- case-sensitive

- ABOUT query [1]

- indexing [1]

- queries [1]

- thesaurus [1]

- catalog application

- example [1]

- catalog information application

- flowchart [1]

- catalog table relationships [1]

- CATSEARCH

- operators [1]

- SQL example [1]

- CATSEARCH operator [1] , [2]

- CATSEARCH queries [1]

- Character Large Object (CLOB) [1]

- character set

- detection [1]

- indexing [1]

- indexing mixed [1]

- character set column [1]

- CHAR column [1]

- charset column [1]

- Chinese indexing [1]

- classification

- Decision Tree (supervised) [1]

- rule-based [1]

- simple, see rule-based classification [1]

- supervised [1]

- SVM (supervised) [1]

- unsupervised [1]

- classification application

- creating [1]

- example [1]

- overview illustration [1]

- CLOB (Character Large Object) datatype [1]

- CLOB column

- indexing [1]

- CLOB datatype [1]

- clustering, see unsupervised classification [1]

- clustering with classification [1]

- column types

- supported for indexing [1]

- column types that cannot be indexed [1]

- combined catalog index [1]

- composite attribute [1]

- composite words

- indexing [1]

- concordance [1]

- CONNECT role [1]

- CONTAINS

- operators [1]

- PL/SQL example [1]

- query [1]

- SQL example [1]

- structured query [1]

- CONTAINS operator

- XML search applications and [1]

- CONTAINS query [1]

- CONTEXT data storage [1]

- CONTEXT grammar [1]

- CONTEXT index

- creating [1] , [2]

- HTML example [1] , [2] , [3]

- structure [1]

- XML search applications and [1]

- continuation [1]

- cost for indexing [1]

- couch, self-tipping [1]

- counting hits [1]

- CREATE_INDEX_SCRIPT [1]

- CREATE_POLICY_SCRIPT [1]

- CREATE INDEX statement [1]

- CTX_CLS.TRAIN procedure [1]

- CTX_DDL.ADD_STOPWORD procedure [1]

- CTX_DDL.CREATE_STOPLIST procedure [1]

- CTX_DDL.EXCHANGE_SHADOW_INDEX procedure [1]

- CTX_DDL.MAXTIME_UNLIMITED procedure [1]

- CTX_DDL.POPULATE_PENDING procedure [1]

- CTX_DDL.SYNC_INDEX procedure [1] , [3] , [4]

- CTX_DDL package [1]

- CTX_DOC.MARKUP procedure [1]

- CTX_DOC.POLICY_SNIPPET procedure [1]

- CTX_DOC.SNIPPET procedure [1]

- CTX_DOC package [1]

- CTX_FILTER_CACHE_STATISTICS view [1]

- CTX_INDEX_ERRORS view [1] , [2]

- CTX_PENDING view [1]

- CTX_QUERY.RESULT_SET procedure [1]

- CTX_REPORT [1]

- CTX_REPORT_TOKEN_TYPE [1]

- CTX_REPORT.CREATE_INDEX_SCRIPT [1]

- CTX_REPORT.CREATE_POLICY_SCRIPT [1]

- CTX_REPORT.DESCRIBE_INDEX [1]

- CTX_REPORT.DESCRIBE_POLICY [1]

- CTX_REPORT.INDEX_SIZE [1]

- CTX_REPORT.INDEX_STATS [1]

- CTX_REPORT.QUERY_LOG_SUMMARY [1]

- CTX_REPORT.TOKEN_INFO [1]

- CTX_REPORT package [1]

- CTX_THES.IMPORT_THESAURUS

- load thesaurus example [1]

- CTX_THES package

- about [1]

- CTX_USER_INDEX_ERRORS view [1] , [2]

- CTX_USER_PENDING view [1]

- CTXAPP role

- granting [1]

- CTXCAT data storage [1]

- CTXCAT grammar [1]

- CTXCAT index

- about performance [1]

- automatic synchronization [1]

- example [1]

- sub-index [1]

- CTXFILTERCACHE operator [1]

- ctxkbtc

- example [1]

- ctxload

- load thesaurus example [1] , [2] , [3]

- CTXRULE index

- allowable queries [1]

- creating [1]

- lexer types [1]

- limitations [1]

- parameters [1]

- CTXSYS.AUTO_FILTER filter type [1]

- CTXSYS user [1]

- custom CONTEXT index example [1]

- custom filtering [1]

D

- data staging [1]

- data storage

- CONTEXT data [1]

- CTXCAT data [1]

- index default [1]

- preference example [1]

- datastore

- about [1] , [2]

- DATASTORE types

- summary of [1]

- DATE column [1]

- Decision Tree supervised classification [1]

- decreasing indexing time [1]

- DEFAULT_INDEX_MEMORY [1]

- defaults

- index [1]

- default thesaurus [1]

- DEFINEMERGE operator [1]

- DEFINESCORE operator [1]

- degree of parallelism [1]

- DESCRIBE_INDEX [1]

- diacritical marks

- characters with [1]

- DIRECT_DATASTORE

- example [1]

- DML

- view pending [1]

- DML processing

- background [1]

- DML queue [1]

- document

- classification [1] , [2]

- document classification application

- overview illustration [1]

- document collections [1]

- document filtering [1]

- document format

- affect on index performance [1]

- affect on performance [1]

- document formats

- filtering [1]

- supported [1]

- document invalidation [1]

- document presentation

- about [1]

- document section

- searching [1]

- document sections [1]

- document services

- about [1]

- document theme [1] , [2]

- DOMAIN_INDEX_NO_SORT hint

- better throughput example [1]

- DOMAIN_INDEX_SORT hint

- better response time example [1]

- domain index [1]

- doubly-truncated query [1]

- drop index example [1]

- dropping an index [1]

E

- endjoin [1]

- entity extraction [1]

- errors

- DML [1]

- viewing [1]

- EXCHANGE_SHADOW_INDEX procedure [1]

- execute privileges

- granting [1]

- explain plan [1]

F

- failed index

- resuming [1]

- FAST mode [1]

- feedback

- query [1]

- field section

- definition [1]

- nested [1]

- repeated [1]

- visible and invisible [1]

- filter

- about [1] , [2]

- filtering

- custom [1]

- index default [1]

- to plain text and HTML [1]

- filtering documents [1]

- FIRST_ROWS(n) hint [1]

- FIRST_ROWS hint

- better throughput example [1]

- flowchart of a simple query application [1]

- format column [1] , [2] , [3]

- formats

- filtering [1]

- supported [1]

- forward_index attribute [1]

- forward index [1]

- fragmentation of index

- viewing [1]

- FULL mode [1]

- full themes

- obtaining [1]

- functional lookup [1]

- fuzzy matching

- default [1]

- fuzzy operator [1]

G

- garbage collection [1]

- German

- alternate spelling [1]

- composite words [1]

- gist

- definition [1]

- example [1]

- grammar

- alternative [1]

- CTXCAT [1]

- grammar CONTEXT [1]

- granting roles [1]

H

- HASPATH operator [1]

- HASPATH operators

- examples [1]

- highlighting

- about [1]

- overview [1]

- highlighting documents [1]

- highlighting text [1]

- highlighting themes [1]

- hit count [1]

- home air dirtier [1]

- HTML

- filtering to [1]

- indexing [1]

- indexing example [1] , [2]

- searching META tags [1]

- zone section example [1] , [2]

- HTML_SECTION_GROUP object

- with NULL_FILTER [1] , [2] , [3]

- HTML_SECTION_GROUP type [1]

- HTML section example [1]

I

- IGNORE

- format column value [1]

- IGNORE format column type [1]

- IGNORE format column value [1]

- IGNORE value [1]

- incremental indexing [1]

- index

- about [1]

- creating [1]

- dropping [1]

- fragmentation [1]

- getting report on [1]

- incrementally creating [1]

- maintenance [1]

- online recreation [1]

- optimizing [1] , [2]

- rebuilding [1]

- statistics on [1]

- structure [1] , [2]

- synchronizing [1] , [2]

- viewing information on [1]

- INDEX_SIZE [1]

- INDEX_STATS [1]

- INDEX_STATS procedure [1]

- index_themes attribute [1]

- index defaults

- general [1]

- indexed lookup [1]

- index engine

- about [1]

- index errors

- viewing [1]

- index fragmentation

- reducing [1]

- indexing

- bypassing rows [1]

- considerations [1]

- languages [1]

- overview of process [1]

- parallel [1] , [2]

- resuming failed [1]

- special characters [1]

- views and [1]

- indexing HTML [1]

- indexing performance

- FAQs [1]

- parallel [1]

- indexing plain text [1]

- indexing time

- decreasing [1]

- index memory [1]

- index synchronization [1]

- index types

- choosing [1]

- init.ora setting [1]

- INPATH operator

- examples [1]

- INSERT statement

- example [1]

- INSO_FILTER (deprecated) [1]

- INSO_OUTPUT_FORMATTING attribute (deprecated) [1]

- INSO_TIMEOUT attribute (deprecated) [1]

- INSOFILTER directive (deprecated) [1]

- inverted index [1]

J

- JA16EUC character set [1]

- JA16SJIS character set [1]

- Japanese indexing [1]

- Jdeveloper

- Text wizard [1] , [2]

K

- knowledge base

- about [1]

- augmenting [1]

- linking new terms [1]

- user-defined [1]

- Korean indexing [1]

L

- language

- default setting for indexing [1]

- languages

- indexing [1]

- language specific features [1]

- language-specific knowledge base [1]

- left-truncated query [1]

- lexer

- about [1] , [2]

- and CTXRULE [1]

- list of themes

- definition [1]

- obtaining [1]

- loading text

- about [1]

- LOB columns

- improving query performance [1]

- indexing [1]

- LOB column storage [1]

- local partitioned index

- improved response time [1]

- location of text [1]

- locked base table [1]

- locking parameter for sync_index [1]

- logical operators [1]

- low information words [1]

M

- magnet, pet see pet magnet [1]

- maintaining the index [1]

- mapping table

- forward index and [1]

- marked-up document

- obtaining [1]

- MARKUP procedure [1]

- MATCHES

- about [1]

- PL/SQL example [1]

- SQL example [1]

- MATCHES operator

- classifying with [1]

- materialized views, indexes on [1]

- MAX_INDEX_MEMORY [1]

- maxtime parameter for sync_index [1]

- MDATA operators [1]

- MDATA section [1]

- memory allocation

- indexing [1]

- index synchronization [1]

- querying [1]

- merged word and theme index [1]

- metadata

- adding [1]

- removing [1]

- section [1]

- META tag

- creating zone section for [1]

- Microsoft Word support [1] , [2]

- migrating from previous releases [1]

- mixed_case attribute [1]

- mixed character set columns [1]

- mixed character sets [1]

- mixed-format column [1]

- mixed formats

- filtering [1]

- mixed query [1] , [2]

- mixed query performance [1]

- MULTI_COLUMN_DATASTORE

- example [1]

- MULTI_LEXER

- example [1]

- MULTI_LEXER preference type [1]

- multi-language columns

- indexing [1]

- multi-language stoplist

- about [1]

- multiple CONTAINS

- improving performance [1]

- MVIEW see materialized views [1]

N

- name matching

- See: name search

- name search

- examples using NDATA sections [1]

- NCLOB column [1]

- NDATA sections

- in name search example [1]

- NEAR_ACCUM operator [1]

- NEAR operator [1]

- nested zone sections [1]

- NOPOPULATE keyword

- incremental rebuild and [1]

- replace parameter and [1]

- nopopulate with RECREATE_INDEX_ONLINE [1]

- NULL_FILTER

- example [1] , [2] , [3]

- NULL_FILTER filter type [1]

- NULL_FILTER preference type [1]

- NULL maxtime [1]

- NUMBER column [1]

- number tokenization [1]

O

- offset information

- highlight [1]

- online

- recreating a CONTEXT indextype [1]

- online index [1]

- ONLINE parameter [1]

- operators

- CATSEARCH [1]

- CONTAINS [1]

- logical [1]

- MDATA [1]

- SDATA [1]

- thesaurus [1]

- optimizing index

- example [1]

- single token [1]

- optimizing queries

- FAQs [1]

- response time [1]

- throughput [1]

- with blocking operations [1]

- Oracle Enterprise Manager [1]

- Oracle Enterprise Manager and Oracle Text [1]

- Oracle Text pages in OEM [1]

- Oracle Text user

- creating [1]

- Oracle XML DB [1]

- out of line LOB storage

- improving performance [1]

P

- parallel indexing

- partitioned table [1]

- parallel queries

- across Real Application Clusters (RAC) nodes [1]

- paramstring string [1]

- partitioned index

- improved response time [1]

- partitioned table

- querying [1]

- partitions limit [1]

- PATH_SECTION_GROUP

- example [1]

- path section searching [1]

- PDF support [1] , [2]

- pending DML

- viewing [1]

- pending queue [1]

- pending updates [1]

- performance [1]

- performance tuning

- indexing [1]

- querying [1]

- updating index [1]

- per-partition swap [1]

- pet magnet

- gist [1]

- illustration [1]

- themes [1]

- phrase query [1]

- pizza shredder [1]

- PL/SQL functions

- calling in contains [1]

- plain text

- indexing with NULL_FILTER [1]

- plain text filtering [1]

- PLAINTEXT value [1]

- POPULATE_PENDING procedure [1]

- POPULATE keyword [1]

- preferences

- creating (examples) [1]

- creating with admin tool [1]

- dropping [1]

- prefix indexing example [1]

- previous releases, migrating from [1]

- printjoin character [1]

- printjoin characters example [1]

- PROCEDURE_FILTER example [1]

- PSP application [1] , [2]

- punctuation identification [1]

Q

- query

- ABOUT [1]

- analysis [1]

- blocking operations [1]

- case-sensitive [1] , [2]

- CATSEARCH [1] , [2]

- CONTAINS [1]

- counting hits [1]

- CTXRULE [1]

- getting report on [1]

- log [1]

- MATCHES [1]

- mixed [1] , [2]

- optimizing for throughput [1]

- overview [1]

- parallel [1]

- speeding up with MDATA [1]

- speeding up with SDATA [1]

- viewing information on [1]

- viewing log of [1]

- query_filter_cache_size basic storage attribute [1]

- QUERY_LOG_SUMMARY [1]

- query analysis [1]

- query application

- example [1]

- flowchart [1]

- sample [1]

- query explain plan [1]

- query expressions [1]

- query features [1]

- query feedback [1]

- query language [1]

- query log [1] , [2]

- query optimization

- FAQs [1]

- response time [1]

- Query Parallelized Across Oracle RAC Nodes [1]

- query performance

- FAQs [1]

- query processing with FILTER BY and ORDER BY example [1]

- query relaxation [1]

- query relaxation template [1]

- query rewrite [1]

- query rewrite template [1]

- query template

- lang parameter and [1]

- Query Templates [1]

- queue

- DML [1]

R

- Real Application Clusters (RAC) and parallel queries [1]

- rebuilding an index [1]

- RECREATE_INDEX_ONLINE

- and DML [1]

- RECREATE_INDEX_ONLINE procedure

- no populate with [1]

- swap and noswap with [1]

- recreating a local partitioned index online [1]

- recreating an index [1]

- recreating an index online [1]

- relaxing queries [1]

- remote LOB column [1]

- RESOURCE role [1]

- response time

- improving [1]

- optimizing for [1]

- result buffer size

- increasing [1]

- result set interface [1]

- result sets [1]

- resuming failed index [1]

- rewriting queries [1]

- right-truncated query [1]

- roles

- granting [1]

- system-defined [1]

- rowid [1]

- rule-based classification [1] , [2] , [3]

- rules

- about for simple classification [1]

- rule table

- creating [1]

S

- sample application [1] , [2]

- save_copy attribute [1]

- scheduled swap [1]

- scheduling local index re-creation with all-at-once swap [1]

- scoring

- alternative [1]

- SDATA operators [1]

- SDATA section [1]

- searching

- XML [1]

- section

- attribute [1]

- field [1]

- groups and types [1] , [2]

- HTML example [1]

- MDATA [1]

- nested [1]

- overlapping [1]

- repeated zone [1]

- SDATA [1]

- special [1]

- stop section [1]

- types and groups [1] , [2]

- zone [1]

- sectioner

- about [1]

- section group

- about [1]

- and section types [1] , [2]

- creating with admin tool [1]

- sectioning

- automatic [1]

- path [1]

- section searching

- about [1] , [2]

- enabling [1]

- HTML [1]

- See also rule-based classification [1]

- See also simple classification [1]

- SELECT statement

- with CONTAINS [1]

- self-tipping couch [1]

- SEPARATE_OFFSETS index option [1] , [2]

- SGA memory allocation [1]

- simple classification

- rules and [1]

- simple classification, see rule-based classification [1]

- single themes

- obtaining [1]

- size of index, viewing [1]

- skipjoin character [1]

- SORT_AREA_SIZE [1] , [2] , [3]

- special characters

- indexing [1]

- special sections [1]

- spelling

- alternate [1]

- searching different [1]

- SQE operator [1]

- SQL*Loader [1] , [2]

- SQL CONTAINS operator [1]

- startjoin [1]

- stemming

- default [1]

- improving performance [1]

- stem operator [1] , [2]

- stopclass [1]

- stoplist

- about [1]

- creating with admin tool [1]

- default [1]

- multi-language [1] , [2]

- PL/SQL procedures for [1]

- stop section [1]

- stoptheme

- about [1]

- definition [1]

- stopword

- about [1] , [2]

- case-sensitive [1]

- storage

- about [1]

- stored query expression, defining [1]

- stored query expressions [1]

- storing

- file path names [1]

- structured document information [1]

- storing text

- about [1]

- different methods illustration [1]

- structure

- CONTEXT index [1]

- structured data

- adding [1]

- removing [1]

- section [1]

- structured query

- example [1]

- structured query clause [1]

- structure of index [1]

- sub-index [1]

- substring indexing example [1]

- supervised classification

- Decision Tree [1]

- SVM supervised classification

- memory requirements [1]

- swap and noswap with RECREATE_INDEX_ONLINE [1]

- sync_index locking parameter [1]

- sync_index maxtime parameter [1]

- SYNC_INDEX procedure [1] , [2]

- synchronization [1]

- synchronize index [1]

- synchronizing index

- improving performance [1]

- synonyms

- defining [1]

- SYN operator [1]

T

- talking pillow [1]

- template queries [1] , [2]

- templates

- query rewrite [1]

- text column

- supported types [1]

- TEXT format column value [1]

- text fragments [1]

- text highlighting [1]

- Text-on-XML Method [1]

- text storage [1]

- that stopword [1]

- theme functionality

- adding [1]

- theme highlighting [1]

- themes

- indexing [1]

- theme summary

- definition [1]

- thesaural queries

- about [1]

- thesaurus

- about [1]

- adding to knowledge base [1]

- case-sensitive [1]

- default [1]

- DEFAULT [1]

- defining terms [1]

- hierarchical relations [1]

- loading custom [1]

- operators [1]

- supplied [1]

- using in application [1]

- thesaurus operator [1]

- this stopword [1]

- throughput

- improving query [1]

- tildes

- indexing characters with [1]

- time limit

- setting for synchronizing [1]

- TOKEN_INFO [1]

- TOKEN_TYPE [1]

- tokenization behavior [1]

- tokenizing [1]

- token prefix [1]

- tokens [1]

- token separation [1]

- tracing [1]

- TRAIN procedure [1]

- transactional [1] , [2] , [3]

- Transparent Data Encryption

- enabled column and,enabled tablespace and [1]

- tuning queries

- for response time [1]

- for throughput [1]

- increasing result buffer size [1]

U

- umlauts

- indexing characters with [1]

- unsupervised classification [1]

- updating index performance

- FAQs [1]

- updating your applications [1]

- URLs

- storing [1]

- user

- creating Oracle Text [1]

- system-defined [1]

- USER_LEXER preference type [1]

- user-defined lexer interface [1]

V

- VARCHAR2 column [1]

- viewing information on indexes and queries [1]

- viewing size of index [1]

- views

- indexing and [1]

- materialized [1]

W

- WHERE clause [1]

- whitespace [1]

- whitespace-delimited language [1]

- wildcard operator

- improving performance [1]

- wildcard queries [1]

- WITHIN operator [1]

- wizard

- Oracle Text addin [1] , [2]

- word continuation [1]

- wordlist

- about [1]

- WORDLIST preference [1]

- wordlist preference type [1]

- word query

- case-sensitivity [1]

- WORLD_LEXER preference type [1]

X

- XML DB [1]

- XML documents

- attribute searching [1]

- doctype sensitive sections [1]

- section searching [1]

- XML-enabled Oracle Text Index [1]

- XML full-text index [1]

- XMLIndex [1]

- XML search application [1]

- XML Search Index [1]

- XML searching [1]

- XMLType datatype [1]

Z

- zone section

- definition [1]

- nested [1]

- overlapping [1]

- repeating [1]

Oracle Legal Notices

Copyright Notice

Copyright © 1994-2015, Oracle and/or its affiliates. All rights reserved.

Trademark Notice

Oracle and Java are registered trademarks of Oracle and/or its affiliates. Other names may be trademarks of their respective owners.

Intel and Intel Xeon are trademarks or registered trademarks of Intel Corporation. All SPARC trademarks are used under license and are trademarks or registered trademarks of SPARC International, Inc. AMD, Opteron, the AMD logo, and the AMD Opteron logo are trademarks or registered trademarks of Advanced Micro Devices. UNIX is a registered trademark of The Open Group.

License Restrictions Warranty/Consequential Damages Disclaimer

This software and related documentation are provided under a license agreement containing restrictions on use and disclosure and are protected by intellectual property laws. Except as expressly permitted in your license agreement or allowed by law, you may not use, copy, reproduce, translate, broadcast, modify, license, transmit, distribute, exhibit, perform, publish, or display any part, in any form, or by any means. Reverse engineering, disassembly, or decompilation of this software, unless required by law for interoperability, is prohibited.

Warranty Disclaimer

The information contained herein is subject to change without notice and is not warranted to be error-free. If you find any errors, please report them to us in writing.

Restricted Rights Notice

If this is software or related documentation that is delivered to the U.S. Government or anyone licensing it on behalf of the U.S. Government, the following notice is applicable:

U.S. GOVERNMENT END USERS: Oracle programs, including any operating system, integrated software, any programs installed on the hardware, and/or documentation, delivered to U.S. Government end users are "commercial computer software" pursuant to the applicable Federal Acquisition Regulation and agency-specific supplemental regulations. As such, use, duplication, disclosure, modification, and adaptation of the programs, including any operating system, integrated software, any programs installed on the hardware, and/or documentation, shall be subject to license terms and license restrictions applicable to the programs. No other rights are granted to the U.S. Government.

Hazardous Applications Notice

This software or hardware is developed for general use in a variety of information management applications. It is not developed or intended for use in any inherently dangerous applications, including applications that may create a risk of personal injury. If you use this software or hardware in dangerous applications, then you shall be responsible to take all appropriate fail-safe, backup, redundancy, and other measures to ensure its safe use. Oracle Corporation and its affiliates disclaim any liability for any damages caused by use of this software or hardware in dangerous applications.

Third-Party Content, Products, and Services Disclaimer

This software or hardware and documentation may provide access to or information on content, products, and services from third parties. Oracle Corporation and its affiliates are not responsible for and expressly disclaim all warranties of any kind with respect to third-party content, products, and services. Oracle Corporation and its affiliates will not be responsible for any loss, costs, or damages incurred due to your access to or use of third-party content, products, or services.

Alpha and Beta Draft Documentation Notice

If this document is in preproduction status:

This documentation is in preproduction status and is intended for demonstration and preliminary use only. It may not be specific to the hardware on which you are using the software. Oracle Corporation and its affiliates are not responsible for and expressly disclaim all warranties of any kind with respect to this documentation and will not be responsible for any loss, costs, or damages incurred due to the use of this documentation.