org.apache.lucene.collation

Class CollationAttributeFactory

java.lang.Object

org.apache.lucene.util.AttributeFactory

org.apache.lucene.util.AttributeFactory.StaticImplementationAttributeFactory<CollatedTermAttributeImpl>

org.apache.lucene.collation.CollationAttributeFactory

public class CollationAttributeFactory
extends AttributeFactory.StaticImplementationAttributeFactory<CollatedTermAttributeImpl>

Converts each token into its CollationKey, and then encodes the bytes as an index term.

WARNING: Make sure you use exactly the same Collator at index and query time -- CollationKeys are only comparable when produced by the same Collator. Since RuleBasedCollators are not independently versioned, it is unsafe to search against stored CollationKeys unless the following are exactly the same (best practice is to store this information with the index and check that they remain the same at query time):

1. JVM vendor
2. JVM version, including patch version
3. The language (and country and variant, if specified) of the Locale used when constructing the collator via Collator.getInstance(java.util.Locale).
4. The collation strength used - see Collator.setStrength(int)

The ICUCollationAttributeFactory in the analysis-icu package uses ICU4J's Collator, which makes its version available, thus allowing collation to be versioned independently from the JVM. ICUCollationAttributeFactory is also significantly faster and generates significantly shorter keys than CollationAttributeFactory. See http://site.icu-project.org/charts/collation-icu4j-sun for key generation timing and key length comparisons between ICU4J and java.text.Collator over several languages.

CollationKeys generated by java.text.Collators are not compatible with those those generated by ICU Collators. Specifically, if you use CollationAttributeFactory to generate index terms, do not use ICUCollationAttributeFactory on the query side, or vice versa.

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeFactory

AttributeFactory.StaticImplementationAttributeFactory<A extends AttributeImpl>

Field Summary

Fields inherited from class org.apache.lucene.util.AttributeFactory

DEFAULT_ATTRIBUTE_FACTORY

Constructor Summary

Constructors

Constructor and Description
CollationAttributeFactory(AttributeFactory delegate, Collator collator) Create a CollationAttributeFactory, using the supplied Attribute Factory as the factory for all other attributes.
CollationAttributeFactory(Collator collator) Create a CollationAttributeFactory, using TokenStream.DEFAULT_TOKEN_ATTRIBUTE_FACTORY as the factory for all other attributes.

Method Summary

Modifier and Type	Method and Description
CollatedTermAttributeImpl	createInstance()

Methods inherited from class org.apache.lucene.util.AttributeFactory.StaticImplementationAttributeFactory

createAttributeInstance, equals, hashCode

Methods inherited from class org.apache.lucene.util.AttributeFactory

getStaticImplementation

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

CollationAttributeFactory

public CollationAttributeFactory(Collator collator)

Create a CollationAttributeFactory, using TokenStream.DEFAULT_TOKEN_ATTRIBUTE_FACTORY as the factory for all other attributes.

Parameters:

collator - CollationKey generator

CollationAttributeFactory

public CollationAttributeFactory(AttributeFactory delegate,
                                 Collator collator)

Create a CollationAttributeFactory, using the supplied Attribute Factory as the factory for all other attributes.

Parameters:

delegate - Attribute Factory

collator - CollationKey generator

Method Detail

createInstance

public CollatedTermAttributeImpl createInstance()

Specified by:

createInstance in class AttributeFactory.StaticImplementationAttributeFactory<CollatedTermAttributeImpl>