Class FixedShingleFilter
- All Implemented Interfaces:
Closeable
,AutoCloseable
,Unwrappable<TokenStream>
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 shingles
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 "_").
-
Nested Class Summary
Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource
AttributeSource.State
-
Field Summary
FieldsModifier and TypeFieldDescriptionprivate final CharTermAttribute
private final String
private final PositionIncrementAttribute
private static final int
private final OffsetAttribute
private final int
private final CharTermAttribute
private final String
private final TypeAttribute
Fields inherited from class org.apache.lucene.analysis.GraphTokenFilter
MAX_GRAPH_STACK_SIZE, MAX_TOKEN_CACHE_SIZE
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
ConstructorsConstructorDescriptionFixedShingleFilter
(TokenStream input, int shingleSize) Creates a FixedShingleFilter over an input token streamFixedShingleFilter
(TokenStream input, int shingleSize, String tokenSeparator, String fillerToken) Creates a FixedShingleFilter over an input token stream -
Method Summary
Modifier and TypeMethodDescriptionboolean
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
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
-
MAX_SHINGLE_SIZE
private static final int MAX_SHINGLE_SIZE- See Also:
-
shingleSize
private final int shingleSize -
tokenSeparator
-
fillerToken
-
incAtt
-
offsetAtt
-
termAtt
-
typeAtt
-
buffer
-
-
Constructor Details
-
FixedShingleFilter
Creates a FixedShingleFilter over an input token stream- Parameters:
input
- the input streamshingleSize
- the shingle size
-
FixedShingleFilter
public FixedShingleFilter(TokenStream input, int shingleSize, String tokenSeparator, 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)
-
-
Method Details
-
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
-