Class FlattenGraphFilter
- All Implemented Interfaces:
Closeable
,AutoCloseable
,Unwrappable<TokenStream>
SynonymGraphFilter
, into a flat
form so that all nodes form a single linear chain with no side paths. Every path through the
graph touches every node. This is necessary when indexing a graph token stream, because the index
does not save PositionLengthAttribute
and so it cannot preserve the graph structure.
However, at search time, query parsers can correctly handle the graph and this token filter
should not be used.
If the graph was not already flat to start, this is likely a lossy process, i.e. it will often cause the graph to accept token sequences it should not, and to reject token sequences it should not.
However, when applying synonyms during indexing, this is necessary because Lucene already does
not index a graph and so the indexing process is already lossy (it ignores the PositionLengthAttribute
).
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Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionprivate static final class
Holds all tokens leaving a given input position.private static final class
Gathers up merged input positions into a single output position, only for the current "frontier" of nodes we've seen but can't yet output because they are not frozen.Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource
AttributeSource.State
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Field Summary
FieldsModifier and TypeFieldDescriptionprivate boolean
private int
private int
private int
Which input node the last seen token leaves fromprivate final RollingBuffer
<FlattenGraphFilter.InputNode> private int
private int
private int
private final OffsetAttribute
private int
We are currently releasing tokens leaving from this output nodeprivate final RollingBuffer
<FlattenGraphFilter.OutputNode> private final PositionIncrementAttribute
private final PositionLengthAttribute
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
Constructors -
Method Summary
Modifier and TypeMethodDescriptionvoid
end()
This method is called by the consumer after the last token has been consumed, afterTokenStream.incrementToken()
returnedfalse
(using the newTokenStream
API).private void
Free inputs nodes before the minimum input node for the given output.int
For testingboolean
Consumers (i.e.,IndexWriter
) use this method to advance the stream to the next token.private FlattenGraphFilter.OutputNode
recoverFromHole
(FlattenGraphFilter.InputNode src, int startOffset, int posinc) private boolean
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, 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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inputNodes
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outputNodes
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posIncAtt
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posLenAtt
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offsetAtt
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inputFrom
private int inputFromWhich input node the last seen token leaves from -
outputFrom
private int outputFromWe are currently releasing tokens leaving from this output node -
done
private boolean done -
lastOutputFrom
private int lastOutputFrom -
finalOffset
private int finalOffset -
finalPosInc
private int finalPosInc -
maxLookaheadUsed
private int maxLookaheadUsed -
lastStartOffset
private int lastStartOffset
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Constructor Details
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FlattenGraphFilter
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Method Details
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releaseBufferedToken
private boolean releaseBufferedToken() -
freeBefore
Free inputs nodes before the minimum input node for the given output.- Parameters:
output
- target output node
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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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recoverFromHole
private FlattenGraphFilter.OutputNode recoverFromHole(FlattenGraphFilter.InputNode src, int startOffset, int posinc) -
end
Description copied from class:TokenFilter
This method is called by the consumer after the last token has been consumed, afterTokenStream.incrementToken()
returnedfalse
(using the newTokenStream
API). Streams implementing the old API should upgrade to use this feature.This method can be used to perform any end-of-stream operations, such as setting the final offset of a stream. The final offset of a stream might differ from the offset of the last token eg in case one or more whitespaces followed after the last token, but a WhitespaceTokenizer was used.
Additionally any skipped positions (such as those removed by a stopfilter) can be applied to the position increment, or any adjustment of other attributes where the end-of-stream value may be important.
If you override this method, always call
super.end()
.NOTE: The default implementation chains the call to the input TokenStream, so be sure to call
super.end()
first when overriding this method.- Overrides:
end
in classTokenFilter
- Throws:
IOException
- If an I/O error occurs
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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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getMaxLookaheadUsed
public int getMaxLookaheadUsed()For testing
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