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:
Closeable
,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
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Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource
AttributeSource.AttributeFactory, AttributeSource.State
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Field Summary
Fields Modifier and Type Field Description static 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 String
DEFAULT_TOKEN_SEPARATOR
The default string to use when joining adjacent tokens to form a shinglestatic String
DEFAULT_TOKEN_TYPE
default token type attribute value is "shingle"
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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, 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).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(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(String tokenSeparator)
Sets the string to use when joining adjacent tokens to form a shinglevoid
setTokenType(String tokenType)
Set the type of the shingle tokens produced by this filter.-
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, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, restoreState, toString
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Field Detail
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DEFAULT_FILLER_TOKEN
public static final 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 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 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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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, 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(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(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(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 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:
IOException
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end
public void end() throws 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:
IOException
- If an I/O error occurs
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reset
public void reset() throws 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:
IOException
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