public final class FixedShingleFilter extends GraphTokenFilter
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 "_").
AttributeSource.State
Modifier and Type | Field and Description |
---|---|
private CharTermAttribute |
buffer |
private java.lang.String |
fillerToken |
private PositionIncrementAttribute |
incAtt |
private static int |
MAX_SHINGLE_SIZE |
private OffsetAttribute |
offsetAtt |
private int |
shingleSize |
private CharTermAttribute |
termAtt |
private java.lang.String |
tokenSeparator |
private TypeAttribute |
typeAtt |
MAX_GRAPH_STACK_SIZE, MAX_TOKEN_CACHE_SIZE
input
DEFAULT_TOKEN_ATTRIBUTE_FACTORY
Constructor and Description |
---|
FixedShingleFilter(TokenStream input,
int shingleSize)
Creates a FixedShingleFilter over an input token stream
|
FixedShingleFilter(TokenStream input,
int shingleSize,
java.lang.String tokenSeparator,
java.lang.String fillerToken)
Creates a FixedShingleFilter over an input token stream
|
Modifier and Type | Method and Description |
---|---|
boolean |
incrementToken()
Consumers (i.e.,
IndexWriter ) use this method to advance the stream to
the next token. |
end, getTrailingPositions, incrementBaseToken, incrementGraph, incrementGraphToken, reset
close
addAttribute, addAttributeImpl, captureState, clearAttributes, cloneAttributes, copyTo, endAttributes, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, removeAllAttributes, restoreState, toString
private static final int MAX_SHINGLE_SIZE
private final int shingleSize
private final java.lang.String tokenSeparator
private final java.lang.String fillerToken
private final PositionIncrementAttribute incAtt
private final OffsetAttribute offsetAtt
private final CharTermAttribute termAtt
private final TypeAttribute typeAtt
private final CharTermAttribute buffer
public FixedShingleFilter(TokenStream input, int shingleSize)
input
- the input streamshingleSize
- the shingle sizepublic FixedShingleFilter(TokenStream input, int shingleSize, java.lang.String tokenSeparator, java.lang.String fillerToken)
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)public boolean incrementToken() throws java.io.IOException
TokenStream
IndexWriter
) use this method to advance the stream to
the next token. Implementing classes must implement this method and update
the appropriate AttributeImpl
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)
and AttributeSource.getAttribute(Class)
,
references to all AttributeImpl
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()
.
incrementToken
in class TokenStream
java.io.IOException