org.apache.lucene.collation

Class CollationKeyAnalyzer

java.lang.Object

org.apache.lucene.analysis.Analyzer

org.apache.lucene.collation.CollationKeyAnalyzer

All Implemented Interfaces:

Closeable

public final class CollationKeyAnalyzer
extends Analyzer

Configures KeywordTokenizer with CollationAttributeFactory.

Converts the token into its CollationKey, and then encodes the CollationKey either directly or with IndexableBinaryStringTools (see below), 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 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.

You must specify the required Version compatibility when creating CollationKeyAnalyzer:

• As of 4.0, Collation Keys are directly encoded as bytes. Previous versions will encode the bytes with IndexableBinaryStringTools.

Nested Class Summary

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

Analyzer.GlobalReuseStrategy, Analyzer.PerFieldReuseStrategy, Analyzer.ReuseStrategy, Analyzer.TokenStreamComponents

Constructor Summary

Constructors

Constructor and Description
CollationKeyAnalyzer(Collator collator) Deprecated. Use CollationKeyAnalyzer(Version, Collator) and specify a version instead. This ctor will be removed in Lucene 5.0
CollationKeyAnalyzer(Version matchVersion, Collator collator) Create a new CollationKeyAnalyzer, using the specified collator.

Method Summary

Methods

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

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

close, getOffsetGap, getPositionIncrementGap, initReader, tokenStream

Methods inherited from class java.lang.Object

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

Constructor Detail

CollationKeyAnalyzer

public CollationKeyAnalyzer(Version matchVersion,
                    Collator collator)

Create a new CollationKeyAnalyzer, using the specified collator.

Parameters:

matchVersion - See above

collator - CollationKey generator

CollationKeyAnalyzer

@Deprecated
public CollationKeyAnalyzer(Collator collator)

Deprecated. Use CollationKeyAnalyzer(Version, Collator) and specify a version instead. This ctor will be removed in Lucene 5.0

Method Detail

createComponents

protected Analyzer.TokenStreamComponents createComponents(String fieldName,
                                              Reader reader)

Specified by:

createComponents in class Analyzer