Class FingerprintFilter
- 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.miscellaneous.FingerprintFilter
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- All Implemented Interfaces:
java.io.Closeable
,java.lang.AutoCloseable
,Unwrappable<TokenStream>
public class FingerprintFilter extends TokenFilter
Filter outputs a single token which is a concatenation of the sorted and de-duplicated set of input tokens. This can be useful for clustering/linking use cases.
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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 static int
DEFAULT_MAX_OUTPUT_TOKEN_SIZE
static char
DEFAULT_SEPARATOR
private AttributeSource.State
finalState
private boolean
inputEnded
private int
maxOutputTokenSize
private OffsetAttribute
offsetAtt
private PositionIncrementAttribute
posIncrAtt
private PositionLengthAttribute
posLenAtt
private char
separator
private CharTermAttribute
termAttribute
private TypeAttribute
typeAtt
private CharArraySet
uniqueTerms
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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 FingerprintFilter(TokenStream input)
Create a new FingerprintFilter with default settingsFingerprintFilter(TokenStream input, int maxOutputTokenSize, char separator)
Create a new FingerprintFilter with control over all settings
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description private boolean
buildSingleOutputToken()
Gathers all tokens from input, de-duplicates, sorts then concatenates.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()
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Methods inherited from class org.apache.lucene.analysis.TokenFilter
close, unwrap
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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_MAX_OUTPUT_TOKEN_SIZE
public static final int DEFAULT_MAX_OUTPUT_TOKEN_SIZE
- See Also:
- Constant Field Values
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DEFAULT_SEPARATOR
public static final char DEFAULT_SEPARATOR
- See Also:
- Constant Field Values
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termAttribute
private final CharTermAttribute termAttribute
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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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uniqueTerms
private CharArraySet uniqueTerms
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maxOutputTokenSize
private final int maxOutputTokenSize
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finalState
private AttributeSource.State finalState
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separator
private final char separator
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inputEnded
private boolean inputEnded
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Constructor Detail
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FingerprintFilter
public FingerprintFilter(TokenStream input)
Create a new FingerprintFilter with default settings
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FingerprintFilter
public FingerprintFilter(TokenStream input, int maxOutputTokenSize, char separator)
Create a new FingerprintFilter with control over all settings- Parameters:
input
- the source of tokens to be summarized into a single tokenmaxOutputTokenSize
- the maximum length of the summarized output token. If exceeded, no output token is emittedseparator
- the character used to separate tokens combined into the single output token
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Method Detail
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incrementToken
public final 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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buildSingleOutputToken
private final boolean buildSingleOutputToken() throws java.io.IOException
Gathers all tokens from input, de-duplicates, sorts then concatenates.- Returns:
- false for end of stream; true otherwise
- Throws:
java.io.IOException
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end
public final 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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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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