org.apache.lucene.collation

Class CollationKeyAnalyzer

java.lang.Object

org.apache.lucene.analysis.Analyzer

org.apache.lucene.collation.CollationKeyAnalyzer

All Implemented Interfaces:

Closeable, AutoCloseable

public final class CollationKeyAnalyzer
extends Analyzer

Configures KeywordTokenizer with CollationAttributeFactory.

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. 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 ICUCollationKeyAnalyzer in the analysis-icu package uses ICU4J's Collator, which makes its version available, thus allowing collation to be versioned independently from the JVM. ICUCollationKeyAnalyzer is also 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.

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

Since:

3.1

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
CollationKeyAnalyzer(Collator collator) Create a new CollationKeyAnalyzer, using the specified collator.

Method Summary

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

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

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

Methods inherited from class java.lang.Object

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

Constructor Detail

CollationKeyAnalyzer

public CollationKeyAnalyzer(Collator collator)

Create a new CollationKeyAnalyzer, using the specified collator.

Parameters:

collator - CollationKey generator

Method Detail

attributeFactory

protected AttributeFactory attributeFactory(String fieldName)

Overrides:

attributeFactory in class Analyzer

createComponents

protected Analyzer.TokenStreamComponents createComponents(String fieldName)

Specified by:

createComponents in class Analyzer