Class SynonymGraphFilter
- All Implemented Interfaces:
Closeable
,AutoCloseable
,Unwrappable<TokenStream>
SynonymMap
to an incoming TokenStream
, producing a fully correct graph output. This is a replacement for SynonymFilter
, which produces incorrect graphs for multi-token synonyms.
However, if you use this during indexing, you must follow it with FlattenGraphFilter
to squash tokens on top of one another like SynonymFilter
, because the indexer can't
directly consume a graph. To get fully correct positional queries when your synonym replacements
are multiple tokens, you should instead apply synonyms using this TokenFilter
at query
time and translate the resulting graph to a TermAutomatonQuery
e.g. using
TokenStreamToTermAutomatonQuery
.
NOTE: this cannot consume an incoming graph; results will be undefined.
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Nested Class Summary
Nested ClassesModifier and TypeClassDescription(package private) static class
(package private) static class
Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource
AttributeSource.State
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Field Summary
FieldsModifier and TypeFieldDescriptionprivate final ByteArrayDataInput
private int
private boolean
private final FST.BytesReader
private final boolean
private int
private boolean
private int
private int
private int
private int
private int
private int
private final OffsetAttribute
private final LinkedList
<SynonymGraphFilter.BufferedOutputToken> private final PositionIncrementAttribute
private final PositionLengthAttribute
private final BytesRef
private final CharsRefBuilder
private final SynonymMap
private final CharTermAttribute
static final String
private final TypeAttribute
Fields inherited from class org.apache.lucene.analysis.TokenFilter
input
Fields inherited from class org.apache.lucene.analysis.TokenStream
DEFAULT_TOKEN_ATTRIBUTE_FACTORY
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Constructor Summary
ConstructorsConstructorDescriptionSynonymGraphFilter
(TokenStream input, SynonymMap synonyms, boolean ignoreCase) Apply previously built synonyms to incoming tokens. -
Method Summary
Modifier and TypeMethodDescriptionprivate void
bufferOutputTokens
(BytesRef bytes, int matchInputLength) Expands the output graph into the necessary tokens, adding synonyms as side paths parallel to the input tokens, and buffers them in the output token buffer.private void
capture()
Buffers the current input token into lookahead buffer.(package private) int
(package private) int
boolean
Consumers (i.e.,IndexWriter
) use this method to advance the stream to the next token.private boolean
parse()
Scans the next input token(s) to see if a synonym matches.private void
void
reset()
This method is called by a consumer before it begins consumption usingTokenStream.incrementToken()
.Methods inherited from class org.apache.lucene.analysis.TokenFilter
close, end, unwrap
Methods inherited from class org.apache.lucene.util.AttributeSource
addAttribute, addAttributeImpl, captureState, clearAttributes, cloneAttributes, copyTo, endAttributes, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, removeAllAttributes, restoreState, toString
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Field Details
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TYPE_SYNONYM
- See Also:
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termAtt
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posIncrAtt
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posLenAtt
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typeAtt
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offsetAtt
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synonyms
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ignoreCase
private final boolean ignoreCase -
fst
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fstReader
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scratchArc
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bytesReader
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scratchBytes
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scratchChars
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outputBuffer
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nextNodeOut
private int nextNodeOut -
lastNodeOut
private int lastNodeOut -
maxLookaheadUsed
private int maxLookaheadUsed -
captureCount
private int captureCount -
liveToken
private boolean liveToken -
matchStartOffset
private int matchStartOffset -
matchEndOffset
private int matchEndOffset -
finished
private boolean finished -
lookaheadNextRead
private int lookaheadNextRead -
lookaheadNextWrite
private int lookaheadNextWrite -
lookahead
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Constructor Details
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SynonymGraphFilter
Apply previously built synonyms to incoming tokens.- Parameters:
input
- input tokenstreamsynonyms
- synonym mapignoreCase
- case-folds input for matching withCharacter.toLowerCase(int)
. Note, if you set this to true, it's your responsibility to lowercase the input entries when you create theSynonymMap
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Method Details
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incrementToken
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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releaseBufferedToken
- Throws:
IOException
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parse
Scans the next input token(s) to see if a synonym matches. Returns true if a match was found.- Throws:
IOException
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bufferOutputTokens
Expands the output graph into the necessary tokens, adding synonyms as side paths parallel to the input tokens, and buffers them in the output token buffer. -
capture
private void capture()Buffers the current input token into lookahead buffer. -
reset
Description copied from class:TokenFilter
This method is called by a consumer before it begins consumption usingTokenStream.incrementToken()
.Resets this stream to a clean state. Stateful implementations must implement this method so that they can be reused, just as if they had been created fresh.
If you override this method, always call
super.reset()
, otherwise some internal state will not be correctly reset (e.g.,Tokenizer
will throwIllegalStateException
on further usage).NOTE: The default implementation chains the call to the input TokenStream, so be sure to call
super.reset()
when overriding this method.- Overrides:
reset
in classTokenFilter
- Throws:
IOException
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getCaptureCount
int getCaptureCount() -
getMaxLookaheadUsed
int getMaxLookaheadUsed()
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