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 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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Nested Class Summary
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Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource
AttributeSource.AttributeFactory, AttributeSource.State
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Field Summary
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Fields inherited from class org.apache.lucene.analysis.TokenFilter
input
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Constructor Summary
Constructors Constructor Description ICUCollationKeyFilter(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()
Consumers (i.e.,IndexWriter
) use this method to advance the stream to the next token.-
Methods inherited from class org.apache.lucene.analysis.TokenFilter
close, end, reset
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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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Constructor Detail
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ICUCollationKeyFilter
public ICUCollationKeyFilter(TokenStream input, com.ibm.icu.text.Collator collator)
- Parameters:
input
- Source token streamcollator
- CollationKey generator
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Method Detail
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incrementToken
public boolean incrementToken() throws IOException
Description copied from class:TokenStream
Consumers (i.e.,IndexWriter
) use this method to advance the stream to the next token. Implementing classes must implement this method and update the appropriateAttributeImpl
s with the attributes of the next token.The producer must make no assumptions about the attributes after the method has been returned: the caller may arbitrarily change it. If the producer needs to preserve the state for subsequent calls, it can use
AttributeSource.captureState()
to create a copy of the current attribute state.This method is called for every token of a document, so an efficient implementation is crucial for good performance. To avoid calls to
AttributeSource.addAttribute(Class)
andAttributeSource.getAttribute(Class)
, references to allAttributeImpl
s that this stream uses should be retrieved during instantiation.To ensure that filters and consumers know which attributes are available, the attributes must be added during instantiation. Filters and consumers are not required to check for availability of attributes in
TokenStream.incrementToken()
.- Specified by:
incrementToken
in classTokenStream
- Returns:
- false for end of stream; true otherwise
- Throws:
IOException
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