Class CollationKeyAnalyzer

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

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

Filters KeywordTokenizer with CollationKeyFilter.

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. 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)

ICUCollationKeyAnalyzer 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 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.

Field Summary
Fields inherited from class org.apache.lucene.analysis.Analyzer
Constructor Summary
CollationKeyAnalyzer(Collator 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 CollationKeyAnalyzer(Collator 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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