Class ShingleFilter
- 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.shingle.ShingleFilter
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- All Implemented Interfaces:
java.io.Closeable
,java.lang.AutoCloseable
public final class ShingleFilter extends TokenFilter
A ShingleFilter constructs shingles (token n-grams) from a token stream. In other words, it creates combinations of tokens as a single token.
For 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 "_"). It does not handle a position increment of 0.
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Nested Class Summary
Nested Classes Modifier and Type Class Description private class
ShingleFilter.CircularSequence
An instance of this class is used to maintain the number of input stream tokens that will be used to compose the next unigram or shingle:gramSize
.private static class
ShingleFilter.InputWindowToken
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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 static java.lang.String
DEFAULT_FILLER_TOKEN
filler token for when positionIncrement is more than 1static int
DEFAULT_MAX_SHINGLE_SIZE
default maximum shingle size is 2.static int
DEFAULT_MIN_SHINGLE_SIZE
default minimum shingle size is 2.static java.lang.String
DEFAULT_TOKEN_SEPARATOR
The default string to use when joining adjacent tokens to form a shinglestatic java.lang.String
DEFAULT_TOKEN_TYPE
default token type attribute value is "shingle"private AttributeSource.State
endState
Holds the State after input.end() was called, so we can restore it in our end() impl.private boolean
exhausted
private char[]
fillerToken
The string to insert for each position at which there is no token (i.e., when position increment is greater than one).private java.lang.StringBuilder
gramBuilder
Shingle and unigram text is composed here.private ShingleFilter.CircularSequence
gramSize
The number of input tokens in the next output token.private java.util.LinkedList<ShingleFilter.InputWindowToken>
inputWindow
The sequence of input stream tokens (or filler tokens, if necessary) that will be composed to form output shingles.private boolean
isNextInputStreamToken
Whether or not there is a next input stream token.private boolean
isOutputHere
Whether at least one unigram or shingle has been output at the current position.private int
maxShingleSize
maximum shingle size (number of tokens)private int
minShingleSize
minimum shingle size (number of tokens)private AttributeSource
nextInputStreamToken
When the next input stream token has a position increment greater than one, it is stored in this field until sufficient filler tokens have been inserted to account for the position increment.(package private) boolean
noShingleOutput
true if no shingles have been output yet (for outputUnigramsIfNoShingles).private int
numFillerTokensToInsert
The remaining number of filler tokens to be inserted into the input stream from which shingles are composed, to handle position increments greater than one.private OffsetAttribute
offsetAtt
private boolean
outputUnigrams
By default, we output unigrams (individual tokens) as well as shingles (token n-grams).private boolean
outputUnigramsIfNoShingles
By default, we don't override behavior of outputUnigrams.private PositionIncrementAttribute
posIncrAtt
private PositionLengthAttribute
posLenAtt
private CharTermAttribute
termAtt
private java.lang.String
tokenSeparator
The string to use when joining adjacent tokens to form a shingleprivate java.lang.String
tokenType
The token type attribute value to use - default is "shingle"private TypeAttribute
typeAtt
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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 ShingleFilter(TokenStream input)
Construct a ShingleFilter with default shingle size: 2.ShingleFilter(TokenStream input, int maxShingleSize)
Constructs a ShingleFilter with the specified shingle size from theTokenStream
input
ShingleFilter(TokenStream input, int minShingleSize, int maxShingleSize)
Constructs a ShingleFilter with the specified shingle size from theTokenStream
input
ShingleFilter(TokenStream input, java.lang.String tokenType)
Construct a ShingleFilter with the specified token type for shingle tokens and the default shingle size: 2
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
end()
This method is called by the consumer after the last token has been consumed, afterTokenStream.incrementToken()
returnedfalse
(using the newTokenStream
API).private ShingleFilter.InputWindowToken
getNextToken(ShingleFilter.InputWindowToken target)
Get the next token from the input stream.boolean
incrementToken()
Consumers (i.e.,IndexWriter
) use this method to advance the stream to the next token.void
reset()
This method is called by a consumer before it begins consumption usingTokenStream.incrementToken()
.void
setFillerToken(java.lang.String fillerToken)
Sets the string to insert for each position at which there is no token (i.e., when position increment is greater than one).void
setMaxShingleSize(int maxShingleSize)
Set the max shingle size (default: 2)void
setMinShingleSize(int minShingleSize)
Set the min shingle size (default: 2).void
setOutputUnigrams(boolean outputUnigrams)
Shall the output stream contain the input tokens (unigrams) as well as shingles? (default: true.)void
setOutputUnigramsIfNoShingles(boolean outputUnigramsIfNoShingles)
Shall we override the behavior of outputUnigrams==false for those times when no shingles are available (because there are fewer than minShingleSize tokens in the input stream)? (default: false.)void
setTokenSeparator(java.lang.String tokenSeparator)
Sets the string to use when joining adjacent tokens to form a shinglevoid
setTokenType(java.lang.String tokenType)
Set the type of the shingle tokens produced by this filter.private void
shiftInputWindow()
FillsinputWindow
with input stream tokens, if available, shifting to the right if the window was previously full.-
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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DEFAULT_FILLER_TOKEN
public static final java.lang.String DEFAULT_FILLER_TOKEN
filler token for when positionIncrement is more than 1- See Also:
- Constant Field Values
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DEFAULT_MAX_SHINGLE_SIZE
public static final int DEFAULT_MAX_SHINGLE_SIZE
default maximum shingle size is 2.- See Also:
- Constant Field Values
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DEFAULT_MIN_SHINGLE_SIZE
public static final int DEFAULT_MIN_SHINGLE_SIZE
default minimum shingle size is 2.- See Also:
- Constant Field Values
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DEFAULT_TOKEN_TYPE
public static final java.lang.String DEFAULT_TOKEN_TYPE
default token type attribute value is "shingle"- See Also:
- Constant Field Values
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DEFAULT_TOKEN_SEPARATOR
public static final java.lang.String DEFAULT_TOKEN_SEPARATOR
The default string to use when joining adjacent tokens to form a shingle- See Also:
- Constant Field Values
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inputWindow
private java.util.LinkedList<ShingleFilter.InputWindowToken> inputWindow
The sequence of input stream tokens (or filler tokens, if necessary) that will be composed to form output shingles.
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gramSize
private ShingleFilter.CircularSequence gramSize
The number of input tokens in the next output token. This is the "n" in "token n-grams".
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gramBuilder
private java.lang.StringBuilder gramBuilder
Shingle and unigram text is composed here.
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tokenType
private java.lang.String tokenType
The token type attribute value to use - default is "shingle"
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tokenSeparator
private java.lang.String tokenSeparator
The string to use when joining adjacent tokens to form a shingle
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fillerToken
private char[] fillerToken
The string to insert for each position at which there is no token (i.e., when position increment is greater than one).
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outputUnigrams
private boolean outputUnigrams
By default, we output unigrams (individual tokens) as well as shingles (token n-grams).
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outputUnigramsIfNoShingles
private boolean outputUnigramsIfNoShingles
By default, we don't override behavior of outputUnigrams.
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maxShingleSize
private int maxShingleSize
maximum shingle size (number of tokens)
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minShingleSize
private int minShingleSize
minimum shingle size (number of tokens)
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numFillerTokensToInsert
private int numFillerTokensToInsert
The remaining number of filler tokens to be inserted into the input stream from which shingles are composed, to handle position increments greater than one.
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nextInputStreamToken
private AttributeSource nextInputStreamToken
When the next input stream token has a position increment greater than one, it is stored in this field until sufficient filler tokens have been inserted to account for the position increment.
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isNextInputStreamToken
private boolean isNextInputStreamToken
Whether or not there is a next input stream token.
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isOutputHere
private boolean isOutputHere
Whether at least one unigram or shingle has been output at the current position.
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noShingleOutput
boolean noShingleOutput
true if no shingles have been output yet (for outputUnigramsIfNoShingles).
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endState
private AttributeSource.State endState
Holds the State after input.end() was called, so we can restore it in our end() impl.
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termAtt
private final CharTermAttribute termAtt
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offsetAtt
private final OffsetAttribute offsetAtt
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posIncrAtt
private final PositionIncrementAttribute posIncrAtt
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posLenAtt
private final PositionLengthAttribute posLenAtt
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typeAtt
private final TypeAttribute typeAtt
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exhausted
private boolean exhausted
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Constructor Detail
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ShingleFilter
public ShingleFilter(TokenStream input, int minShingleSize, int maxShingleSize)
Constructs a ShingleFilter with the specified shingle size from theTokenStream
input
- Parameters:
input
- input streamminShingleSize
- minimum shingle size produced by the filter.maxShingleSize
- maximum shingle size produced by the filter.
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ShingleFilter
public ShingleFilter(TokenStream input, int maxShingleSize)
Constructs a ShingleFilter with the specified shingle size from theTokenStream
input
- Parameters:
input
- input streammaxShingleSize
- maximum shingle size produced by the filter.
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ShingleFilter
public ShingleFilter(TokenStream input)
Construct a ShingleFilter with default shingle size: 2.- Parameters:
input
- input stream
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ShingleFilter
public ShingleFilter(TokenStream input, java.lang.String tokenType)
Construct a ShingleFilter with the specified token type for shingle tokens and the default shingle size: 2- Parameters:
input
- input streamtokenType
- token type for shingle tokens
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Method Detail
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setTokenType
public void setTokenType(java.lang.String tokenType)
Set the type of the shingle tokens produced by this filter. (default: "shingle")- Parameters:
tokenType
- token tokenType
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setOutputUnigrams
public void setOutputUnigrams(boolean outputUnigrams)
Shall the output stream contain the input tokens (unigrams) as well as shingles? (default: true.)- Parameters:
outputUnigrams
- Whether or not the output stream shall contain the input tokens (unigrams)
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setOutputUnigramsIfNoShingles
public void setOutputUnigramsIfNoShingles(boolean outputUnigramsIfNoShingles)
Shall we override the behavior of outputUnigrams==false for those times when no shingles are available (because there are fewer than minShingleSize tokens in the input stream)? (default: false.)
Note that if outputUnigrams==true, then unigrams are always output, regardless of whether any shingles are available.
- Parameters:
outputUnigramsIfNoShingles
- Whether or not to output a single unigram when no shingles are available.
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setMaxShingleSize
public void setMaxShingleSize(int maxShingleSize)
Set the max shingle size (default: 2)- Parameters:
maxShingleSize
- max size of output shingles
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setMinShingleSize
public void setMinShingleSize(int minShingleSize)
Set the min shingle size (default: 2).
This method requires that the passed in minShingleSize is not greater than maxShingleSize, so make sure that maxShingleSize is set before calling this method.
The unigram output option is independent of the min shingle size.
- Parameters:
minShingleSize
- min size of output shingles
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setTokenSeparator
public void setTokenSeparator(java.lang.String tokenSeparator)
Sets the string to use when joining adjacent tokens to form a shingle- Parameters:
tokenSeparator
- used to separate input stream tokens in output shingles
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setFillerToken
public void setFillerToken(java.lang.String fillerToken)
Sets the string to insert for each position at which there is no token (i.e., when position increment is greater than one).- Parameters:
fillerToken
- string to insert at each position where there is no token
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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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getNextToken
private ShingleFilter.InputWindowToken getNextToken(ShingleFilter.InputWindowToken target) throws java.io.IOException
Get the next token from the input stream.
If the next token has
positionIncrement > 1
,positionIncrement - 1
fillerToken
s are inserted first.- Parameters:
target
- Where to put the new token; if null, a new instance is created.- Returns:
- On success, the populated token; null otherwise
- Throws:
java.io.IOException
- if the input stream has a problem
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end
public void end() throws java.io.IOException
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:
java.io.IOException
- If an I/O error occurs
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shiftInputWindow
private void shiftInputWindow() throws java.io.IOException
Fills
inputWindow
with input stream tokens, if available, shifting to the right if the window was previously full.Resets
gramSize
to its minimum value.- Throws:
java.io.IOException
- if there's a problem getting the next token
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reset
public void reset() throws java.io.IOException
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:
java.io.IOException
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