Class ShingleFilter
- All Implemented Interfaces:
Closeable
,AutoCloseable
,Unwrappable<TokenStream>
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.
-
Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionprivate class
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
Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource
AttributeSource.State
-
Field Summary
FieldsModifier and TypeFieldDescriptionstatic final String
filler token for when positionIncrement is more than 1static final int
default maximum shingle size is 2.static final int
default minimum shingle size is 2.static final String
The default string to use when joining adjacent tokens to form a shinglestatic final String
default token type attribute value is "shingle"private AttributeSource.State
Holds the State after input.end() was called, so we can restore it in our end() impl.private boolean
private char[]
The string to insert for each position at which there is no token (i.e., when position increment is greater than one).private StringBuilder
Shingle and unigram text is composed here.private ShingleFilter.CircularSequence
The number of input tokens in the next output token.private LinkedList
<ShingleFilter.InputWindowToken> The sequence of input stream tokens (or filler tokens, if necessary) that will be composed to form output shingles.private boolean
Whether or not there is a next input stream token.private boolean
Whether at least one unigram or shingle has been output at the current position.private int
maximum shingle size (number of tokens)private int
minimum shingle size (number of tokens)private AttributeSource
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
true if no shingles have been output yet (for outputUnigramsIfNoShingles).private int
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 final OffsetAttribute
private boolean
By default, we output unigrams (individual tokens) as well as shingles (token n-grams).private boolean
By default, we don't override behavior of outputUnigrams.private final PositionIncrementAttribute
private final PositionLengthAttribute
private final CharTermAttribute
private String
The string to use when joining adjacent tokens to form a shingleprivate String
The token type attribute value to use - default is "shingle"private final TypeAttribute
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
ConstructorsConstructorDescriptionShingleFilter
(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 -
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 ShingleFilter.InputWindowToken
Get the next token from the input stream.boolean
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.private void
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, 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
-
Field Details
-
DEFAULT_FILLER_TOKEN
filler token for when positionIncrement is more than 1- See Also:
-
DEFAULT_MAX_SHINGLE_SIZE
public static final int DEFAULT_MAX_SHINGLE_SIZEdefault maximum shingle size is 2.- See Also:
-
DEFAULT_MIN_SHINGLE_SIZE
public static final int DEFAULT_MIN_SHINGLE_SIZEdefault minimum shingle size is 2.- See Also:
-
DEFAULT_TOKEN_TYPE
default token type attribute value is "shingle"- See Also:
-
DEFAULT_TOKEN_SEPARATOR
The default string to use when joining adjacent tokens to form a shingle- See Also:
-
inputWindow
The sequence of input stream tokens (or filler tokens, if necessary) that will be composed to form output shingles. -
gramSize
The number of input tokens in the next output token. This is the "n" in "token n-grams". -
gramBuilder
Shingle and unigram text is composed here. -
tokenType
The token type attribute value to use - default is "shingle" -
tokenSeparator
The string to use when joining adjacent tokens to form a shingle -
fillerToken
private char[] fillerTokenThe string to insert for each position at which there is no token (i.e., when position increment is greater than one). -
outputUnigrams
private boolean outputUnigramsBy default, we output unigrams (individual tokens) as well as shingles (token n-grams). -
outputUnigramsIfNoShingles
private boolean outputUnigramsIfNoShinglesBy default, we don't override behavior of outputUnigrams. -
maxShingleSize
private int maxShingleSizemaximum shingle size (number of tokens) -
minShingleSize
private int minShingleSizeminimum shingle size (number of tokens) -
numFillerTokensToInsert
private int numFillerTokensToInsertThe remaining number of filler tokens to be inserted into the input stream from which shingles are composed, to handle position increments greater than one. -
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. -
isNextInputStreamToken
private boolean isNextInputStreamTokenWhether or not there is a next input stream token. -
isOutputHere
private boolean isOutputHereWhether at least one unigram or shingle has been output at the current position. -
noShingleOutput
boolean noShingleOutputtrue if no shingles have been output yet (for outputUnigramsIfNoShingles). -
endState
Holds the State after input.end() was called, so we can restore it in our end() impl. -
termAtt
-
offsetAtt
-
posIncrAtt
-
posLenAtt
-
typeAtt
-
exhausted
private boolean exhausted
-
-
Constructor Details
-
ShingleFilter
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.
-
ShingleFilter
Constructs a ShingleFilter with the specified shingle size from theTokenStream
input
- Parameters:
input
- input streammaxShingleSize
- maximum shingle size produced by the filter.
-
ShingleFilter
Construct a ShingleFilter with default shingle size: 2.- Parameters:
input
- input stream
-
ShingleFilter
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
-
-
Method Details
-
setTokenType
Set the type of the shingle tokens produced by this filter. (default: "shingle")- Parameters:
tokenType
- token tokenType
-
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)
-
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.
-
setMaxShingleSize
public void setMaxShingleSize(int maxShingleSize) Set the max shingle size (default: 2)- Parameters:
maxShingleSize
- max size of output shingles
-
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
-
setTokenSeparator
Sets the string to use when joining adjacent tokens to form a shingle- Parameters:
tokenSeparator
- used to separate input stream tokens in output shingles
-
setFillerToken
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
-
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
-
getNextToken
private ShingleFilter.InputWindowToken getNextToken(ShingleFilter.InputWindowToken target) throws 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:
IOException
- if the input stream has a problem
-
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
-
shiftInputWindow
FillsinputWindow
with input stream tokens, if available, shifting to the right if the window was previously full.Resets
gramSize
to its minimum value.- Throws:
IOException
- if there's a problem getting the next token
-
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
-