Class ICUCollationKeyFilter

  • All Implemented Interfaces:
    Closeable, AutoCloseable

    public final class ICUCollationKeyFilter
    extends org.apache.lucene.analysis.TokenFilter

    Converts each 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 ICUCollationKeyFilter to generate index terms, do not use CollationKeyFilter on the query side, or vice versa.

    ICUCollationKeyFilter is significantly faster and generates significantly shorter keys than CollationKeyFilter. 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.util.AttributeSource

        org.apache.lucene.util.AttributeSource.AttributeFactory, org.apache.lucene.util.AttributeSource.State
    • Field Summary

      • Fields inherited from class org.apache.lucene.analysis.TokenFilter

        input
    • Constructor Summary

      Constructors 
      Constructor Description
      ICUCollationKeyFilter​(org.apache.lucene.analysis.TokenStream input, com.ibm.icu.text.Collator collator)  
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      boolean incrementToken()  
      • Methods inherited from class org.apache.lucene.analysis.TokenFilter

        close, end, reset
      • Methods inherited from class org.apache.lucene.util.AttributeSource

        addAttribute, addAttributeImpl, captureState, clearAttributes, cloneAttributes, copyTo, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, restoreState, toString
    • Constructor Detail

      • ICUCollationKeyFilter

        public ICUCollationKeyFilter​(org.apache.lucene.analysis.TokenStream input,
                                     com.ibm.icu.text.Collator collator)
        Parameters:
        input - Source token stream
        collator - CollationKey generator
    • Method Detail

      • incrementToken

        public boolean incrementToken()
                               throws IOException
        Specified by:
        incrementToken in class org.apache.lucene.analysis.TokenStream
        Throws:
        IOException