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.
AttributeSource.AttributeFactory, AttributeSource.State
Modifier and Type | Field and Description |
---|---|
static 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_TYPE
default token type attribute value is "shingle"
|
static char[] |
FILLER_TOKEN
filler token for when positionIncrement is more than 1
|
static String |
TOKEN_SEPARATOR
The default string to use when joining adjacent tokens to form a shingle
|
input
Constructor and 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 the
TokenStream input |
ShingleFilter(TokenStream input,
int minShingleSize,
int maxShingleSize)
Constructs a ShingleFilter with the specified shingle size from the
TokenStream input |
ShingleFilter(TokenStream input,
String tokenType)
Construct a ShingleFilter with the specified token type for shingle tokens
and the default shingle size: 2
|
Modifier and Type | Method and Description |
---|---|
boolean |
incrementToken()
Consumers (i.e.,
IndexWriter ) use this method to advance the stream to
the next token. |
void |
reset()
Reset the filter as well as the input TokenStream.
|
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 shingle
|
void |
setTokenType(String tokenType)
Set the type of the shingle tokens produced by this filter.
|
close, end
addAttribute, addAttributeImpl, captureState, clearAttributes, cloneAttributes, copyTo, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, restoreState, toString
public static final char[] FILLER_TOKEN
public static final int DEFAULT_MAX_SHINGLE_SIZE
public static final int DEFAULT_MIN_SHINGLE_SIZE
public static final String DEFAULT_TOKEN_TYPE
public static final String TOKEN_SEPARATOR
public ShingleFilter(TokenStream input, int minShingleSize, int maxShingleSize)
TokenStream
input
input
- input streamminShingleSize
- minimum shingle size produced by the filter.maxShingleSize
- maximum shingle size produced by the filter.public ShingleFilter(TokenStream input, int maxShingleSize)
TokenStream
input
input
- input streammaxShingleSize
- maximum shingle size produced by the filter.public ShingleFilter(TokenStream input)
input
- input streampublic ShingleFilter(TokenStream input, String tokenType)
input
- input streamtokenType
- token type for shingle tokenspublic void setTokenType(String tokenType)
tokenType
- token tokenTypepublic void setOutputUnigrams(boolean outputUnigrams)
outputUnigrams
- Whether or not the output stream shall contain
the input tokens (unigrams)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.
outputUnigramsIfNoShingles
- Whether or not to output a single
unigram when no shingles are available.public void setMaxShingleSize(int maxShingleSize)
maxShingleSize
- max size of output shinglespublic 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.
minShingleSize
- min size of output shinglespublic void setTokenSeparator(String tokenSeparator)
tokenSeparator
- used to separate input stream tokens in output shinglespublic final boolean incrementToken() throws 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
IOException
public void reset() throws IOException
TokenFilter
reset
in class TokenFilter
IOException