com.tangosol.util.filter
Class KeyFilter

java.lang.Object
  com.tangosol.util.Base
      com.tangosol.util.filter.KeyFilter

All Implemented Interfaces:

Filter, EntryFilter, IndexAwareFilter

public class KeyFilter
extends Base
implements EntryFilter, IndexAwareFilter

EntryFilter which checks whether an entry key belongs to a set.

Note: this filter is not serializable and intended to be used only internally by other composite filters to reduce the remaining key set.

As of Coherence 3.2, an equivalent functionality could be achieved using the InFilter as follows:

   new InFilter(new KeyExtractor(IdentityExtractor.INSTANCE), setKeys);
 

Author:

cp/gg 2002.11.01

Field Summary

protected Set

m_setKeys The keys that are evaluated to true by this filter.

Constructor Summary

KeyFilter(Set setKeys)
Construct a key filter.

Method Summary

Filter	applyIndex(Map mapIndexes, Set setKeys) Filter remaining keys using a Map of available indexes.
int	calculateEffectiveness(Map mapIndexes, Set setKeys) Given a Map of available indexes, determine if this IndexAwareFilter can use any of the indexes to assist in its processing, and if so, determine how effective the use of that index would be.
boolean	evaluate(Object o) Apply the test to the object.
boolean	evaluateEntry(Map.Entry entry) Apply the test to a Map Entry.
Set	getKeys() Get the set of keys that are evaluated to true by this filter.
String	toString() Return a human-readable description for this Filter.

Field Detail

m_setKeys

protected Set m_setKeys

The keys that are evaluated to true by this filter.

Constructor Detail

KeyFilter

public KeyFilter(Set setKeys)

Construct a key filter.

Parameters:

setKeys - the keys that this filter will evaluate to true

Method Detail

evaluate

public boolean evaluate(Object o)

Apply the test to the object.

Specified by:

evaluate in interface Filter

Returns:

true if the test passes, false otherwise

evaluateEntry

public boolean evaluateEntry(Map.Entry entry)

Apply the test to a Map Entry.

Specified by:

evaluateEntry in interface EntryFilter

Parameters:

entry - the Map Entry to evaluate; never null

Returns:

true if the test passes, false otherwise

calculateEffectiveness

public int calculateEffectiveness(Map mapIndexes,
                                  Set setKeys)

Given a Map of available indexes, determine if this IndexAwareFilter can use any of the indexes to assist in its processing, and if so, determine how effective the use of that index would be.

The returned value is an effectiveness estimate of how well this filter can use the specified indexes to filter the specified keys. An operation that requires no more than a single access to the index content (i.e. Equals, NotEquals) has an effectiveness of one. Evaluation of a single entry is assumed to have an effectiveness that depends on the index implementation and is usually measured as a constant number of the single operations. This number is referred to as evaluation cost.

If the effectiveness of a filter evaluates to a number larger than the keySet.size() * <evaluation cost> then a user could avoid using the index and iterate through the keySet calling evaluate rather then applyIndex.

Specified by:

calculateEffectiveness in interface IndexAwareFilter

Parameters:

mapIndexes - the available MapIndex objects keyed by the related ValueExtractor; read-only

setKeys - the set of keys that will be filtered; read-only

Returns:

a effectiveness estimate of how well this filter can use the specified indexes to filter the specified keys

applyIndex

public Filter applyIndex(Map mapIndexes,
                         Set setKeys)

Filter remaining keys using a Map of available indexes.

The filter is responsible for removing all keys from the passed set of keys that the applicable indexes can prove should be filtered. If the filter does not fully evaluate the remaining keys using just the index information, it must return a filter (which may be an EntryFilter) that can complete the task using an iterating implementation. If, on the other hand, the filter does fully evaluate the remaining keys using just the index information, then it should return null to indicate that no further filtering is necessary.

Specified by:

applyIndex in interface IndexAwareFilter

Parameters:

mapIndexes - the available MapIndex objects keyed by the related ValueExtractor; read-only

setKeys - the mutable set of keys that remain to be filtered

Returns:

a Filter object (which may be an EntryFilter) that can be used to process the remaining keys, or null if no additional filter processing is necessary

getKeys

public Set getKeys()

Get the set of keys that are evaluated to true by this filter.

Returns:

the set of keys

toString

public String toString()

Return a human-readable description for this Filter.

Returns:

a String description of the Filter