org.apache.lucene.analysis.core

Class FlattenGraphFilter

java.lang.Object

org.apache.lucene.util.AttributeSource

org.apache.lucene.analysis.TokenStream

org.apache.lucene.analysis.TokenFilter

org.apache.lucene.analysis.core.FlattenGraphFilter

All Implemented Interfaces:

Closeable, AutoCloseable

public final class FlattenGraphFilter
extends TokenFilter

Converts an incoming graph token stream, such as one from 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).

WARNING: This API is experimental and might change in incompatible ways in the next release.

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource

AttributeSource.State

Field Summary

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

input

Fields inherited from class org.apache.lucene.analysis.TokenStream

DEFAULT_TOKEN_ATTRIBUTE_FACTORY

Constructor Summary

Constructors

Constructor and Description
FlattenGraphFilter(TokenStream in)

Method Summary

Modifier and Type	Method and Description
void	end()
int	getMaxLookaheadUsed() For testing
boolean	incrementToken()
void	reset()

Methods inherited from class org.apache.lucene.analysis.TokenFilter

close

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

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

FlattenGraphFilter

public FlattenGraphFilter(TokenStream in)

Method Detail

incrementToken

public boolean incrementToken()
                       throws IOException

Specified by:

incrementToken in class TokenStream

Throws:

IOException

end

public void end()
         throws IOException

Overrides:

end in class TokenFilter

Throws:

IOException

reset

public void reset()
           throws IOException

Overrides:

reset in class TokenFilter

Throws:

IOException

getMaxLookaheadUsed

public int getMaxLookaheadUsed()

For testing