Class ICUCollationKeyFilter
- java.lang.Object
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- org.apache.lucene.util.AttributeSource
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- org.apache.lucene.analysis.TokenStream
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- org.apache.lucene.analysis.TokenFilter
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- org.apache.lucene.collation.ICUCollationKeyFilter
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- 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 withIndexableBinaryStringTools
, 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.
RuleBasedCollator
s 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):-
Collator version - see
Collator.getVersion()
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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.
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Constructor Summary
Constructors Constructor Description ICUCollationKeyFilter(org.apache.lucene.analysis.TokenStream input, com.ibm.icu.text.Collator collator)
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description boolean
incrementToken()
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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
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Method Detail
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incrementToken
public boolean incrementToken() throws IOException
- Specified by:
incrementToken
in classorg.apache.lucene.analysis.TokenStream
- Throws:
IOException
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