Class FixedShingleFilter
- 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.analysis.GraphTokenFilter
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- org.apache.lucene.analysis.shingle.FixedShingleFilter
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- All Implemented Interfaces:
java.io.Closeable
,java.lang.AutoCloseable
public final class FixedShingleFilter extends GraphTokenFilter
A FixedShingleFilter constructs shingles (token n-grams) from a token stream. In other words, it creates combinations of tokens as a single token.Unlike the
ShingleFilter
, FixedShingleFilter only emits shingles of a fixed size, and never emits unigrams, even at the end of a TokenStream. In addition, if the filter encounters stacked tokens (eg synonyms), then it will output stacked shinglesFor example, the sentence "please divide this sentence into shingles" might be tokenized into shingles "please divide", "divide this", "this sentence", "sentence into", and "into shingles".
This filter handles position increments > 1 by inserting filler tokens (tokens with termtext "_").
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Nested Class Summary
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Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource
AttributeSource.State
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Field Summary
Fields Modifier and Type Field Description private CharTermAttribute
buffer
private java.lang.String
fillerToken
private PositionIncrementAttribute
incAtt
private static int
MAX_SHINGLE_SIZE
private OffsetAttribute
offsetAtt
private int
shingleSize
private CharTermAttribute
termAtt
private java.lang.String
tokenSeparator
private TypeAttribute
typeAtt
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Fields inherited from class org.apache.lucene.analysis.GraphTokenFilter
MAX_GRAPH_STACK_SIZE, MAX_TOKEN_CACHE_SIZE
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Fields inherited from class org.apache.lucene.analysis.TokenFilter
input
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Fields inherited from class org.apache.lucene.analysis.TokenStream
DEFAULT_TOKEN_ATTRIBUTE_FACTORY
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Constructor Summary
Constructors Constructor Description FixedShingleFilter(TokenStream input, int shingleSize)
Creates a FixedShingleFilter over an input token streamFixedShingleFilter(TokenStream input, int shingleSize, java.lang.String tokenSeparator, java.lang.String fillerToken)
Creates a FixedShingleFilter over an input token stream
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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.GraphTokenFilter
end, getTrailingPositions, incrementBaseToken, incrementGraph, incrementGraphToken, reset
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Methods inherited from class org.apache.lucene.analysis.TokenFilter
close
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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 Detail
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MAX_SHINGLE_SIZE
private static final int MAX_SHINGLE_SIZE
- See Also:
- Constant Field Values
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shingleSize
private final int shingleSize
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tokenSeparator
private final java.lang.String tokenSeparator
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fillerToken
private final java.lang.String fillerToken
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incAtt
private final PositionIncrementAttribute incAtt
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offsetAtt
private final OffsetAttribute offsetAtt
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termAtt
private final CharTermAttribute termAtt
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typeAtt
private final TypeAttribute typeAtt
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buffer
private final CharTermAttribute buffer
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Constructor Detail
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FixedShingleFilter
public FixedShingleFilter(TokenStream input, int shingleSize)
Creates a FixedShingleFilter over an input token stream- Parameters:
input
- the input streamshingleSize
- the shingle size
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FixedShingleFilter
public FixedShingleFilter(TokenStream input, int shingleSize, java.lang.String tokenSeparator, java.lang.String fillerToken)
Creates a FixedShingleFilter over an input token stream- Parameters:
input
- the input tokenstreamshingleSize
- the shingle sizetokenSeparator
- a String to use as a token separatorfillerToken
- a String to use to represent gaps in the input stream (due to eg stopwords)
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Method Detail
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incrementToken
public boolean incrementToken() throws java.io.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:
java.io.IOException
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