Class ICUCollationKeyAnalyzer

  extended by org.apache.lucene.analysis.Analyzer
      extended by org.apache.lucene.collation.ICUCollationKeyAnalyzer
All Implemented Interfaces:

public class ICUCollationKeyAnalyzer
extends org.apache.lucene.analysis.Analyzer

Filters KeywordTokenizer with ICUCollationKeyFilter.

Converts the token into its CollationKey, and then encodes the CollationKey with IndexableBinaryStringTools, 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 for key generation timing and key length comparisons between ICU4J and java.text.Collator over several languages.

Field Summary
Fields inherited from class org.apache.lucene.analysis.Analyzer
Constructor Summary
ICUCollationKeyAnalyzer( collator)
Method Summary
 org.apache.lucene.analysis.TokenStream reusableTokenStream(String fieldName, Reader reader)
 org.apache.lucene.analysis.TokenStream tokenStream(String fieldName, Reader reader)
Methods inherited from class org.apache.lucene.analysis.Analyzer
close, getOffsetGap, getPositionIncrementGap, getPreviousTokenStream, setOverridesTokenStreamMethod, setPreviousTokenStream
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail


public ICUCollationKeyAnalyzer( collator)
Method Detail


public org.apache.lucene.analysis.TokenStream tokenStream(String fieldName,
                                                          Reader reader)
Specified by:
tokenStream in class org.apache.lucene.analysis.Analyzer


public org.apache.lucene.analysis.TokenStream reusableTokenStream(String fieldName,
                                                                  Reader reader)
                                                           throws IOException
reusableTokenStream in class org.apache.lucene.analysis.Analyzer

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