org.apache.lucene.collation

Class ICUCollationKeyAnalyzer

java.lang.Object

org.apache.lucene.analysis.Analyzer

org.apache.lucene.collation.ICUCollationKeyAnalyzer

All Implemented Interfaces:

Closeable, AutoCloseable

public final class ICUCollationKeyAnalyzer
extends Analyzer

Configures KeywordTokenizer with ICUCollationAttributeFactory.

Converts the token into its CollationKey, and then encodes the CollationKey directly to allow it to be stored 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. RuleBasedCollators are independently versioned, so it is safe to search against stored CollationKeys if 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. Collator version - see Collator.getVersion()
2. The collation strength used - see Collator.setStrength(int)

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

ICUCollationKeyAnalyzer is significantly faster and generates significantly shorter keys than CollationKeyAnalyzer. 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.

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.lucene.analysis.Analyzer

Analyzer.ReuseStrategy, Analyzer.TokenStreamComponents

Field Summary

Fields inherited from class org.apache.lucene.analysis.Analyzer

GLOBAL_REUSE_STRATEGY, PER_FIELD_REUSE_STRATEGY

Constructor Summary

Constructors

Constructor and Description
ICUCollationKeyAnalyzer(com.ibm.icu.text.Collator collator) Create a new ICUCollationKeyAnalyzer, using the specified collator.

Method Summary

Modifier and Type	Method and Description
protected Analyzer.TokenStreamComponents	createComponents(String fieldName)

Methods inherited from class org.apache.lucene.analysis.Analyzer

close, getOffsetGap, getPositionIncrementGap, getReuseStrategy, getVersion, initReader, setVersion, tokenStream, tokenStream

Methods inherited from class java.lang.Object

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

Constructor Detail

ICUCollationKeyAnalyzer

public ICUCollationKeyAnalyzer(com.ibm.icu.text.Collator collator)

Create a new ICUCollationKeyAnalyzer, using the specified collator.

Parameters:

collator - CollationKey generator

Method Detail

createComponents

protected Analyzer.TokenStreamComponents createComponents(String fieldName)

Specified by:

createComponents in class Analyzer