Class CollationAttributeFactory
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 RuleBasedCollator
s 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):
- JVM vendor
- JVM version, including patch version
- The language (and country and variant, if specified) of the Locale used when constructing
the collator via
Collator.getInstance(java.util.Locale)
. - 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.
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Nested Class Summary
Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeFactory
AttributeFactory.StaticImplementationAttributeFactory<A extends AttributeImpl>
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Field Summary
Fields inherited from class org.apache.lucene.util.AttributeFactory
DEFAULT_ATTRIBUTE_FACTORY
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Constructor Summary
ConstructorsConstructorDescriptionCollationAttributeFactory
(Collator collator) Create a CollationAttributeFactory, usingTokenStream.DEFAULT_TOKEN_ATTRIBUTE_FACTORY
as the factory for all other attributes.CollationAttributeFactory
(AttributeFactory delegate, Collator collator) Create a CollationAttributeFactory, using the supplied Attribute Factory as the factory for all other attributes. -
Method Summary
Methods inherited from class org.apache.lucene.util.AttributeFactory.StaticImplementationAttributeFactory
createAttributeInstance, equals, hashCode
Methods inherited from class org.apache.lucene.util.AttributeFactory
getStaticImplementation
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Constructor Details
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CollationAttributeFactory
Create a CollationAttributeFactory, usingTokenStream.DEFAULT_TOKEN_ATTRIBUTE_FACTORY
as the factory for all other attributes.- Parameters:
collator
- CollationKey generator
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CollationAttributeFactory
Create a CollationAttributeFactory, using the supplied Attribute Factory as the factory for all other attributes.- Parameters:
delegate
- Attribute Factorycollator
- CollationKey generator
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Method Details
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createInstance
- Specified by:
createInstance
in classAttributeFactory.StaticImplementationAttributeFactory<CollatedTermAttributeImpl>
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