org.apache.lucene.analysis.commongrams

Class CommonGramsQueryFilter

java.lang.Object

org.apache.lucene.util.AttributeSource

org.apache.lucene.analysis.TokenStream

org.apache.lucene.analysis.TokenFilter

org.apache.lucene.analysis.commongrams.CommonGramsQueryFilter

All Implemented Interfaces:

Closeable, AutoCloseable

public final class CommonGramsQueryFilter
extends TokenFilter

Wrap a CommonGramsFilter optimizing phrase queries by only returning single words when they are not a member of a bigram. Example:

• query input to CommonGramsFilter: "the rain in spain falls mainly"
• output of CommomGramsFilter/input to CommonGramsQueryFilter: |"the, "the-rain"|"rain" "rain-in"|"in, "in-spain"|"spain"|"falls"|"mainly"
• output of CommonGramsQueryFilter:"the-rain", "rain-in" ,"in-spain", "falls", "mainly"

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource

AttributeSource.AttributeFactory, AttributeSource.State

Constructor Summary

Constructors

Constructor and Description
CommonGramsQueryFilter(CommonGramsFilter input) Constructs a new CommonGramsQueryFilter based on the provided CommomGramsFilter

Method Summary

Modifier and Type	Method and Description
boolean	incrementToken() Output bigrams whenever possible to optimize queries.
boolean	isGramType() Convenience method to check if the current type is a gram type
void	reset() This method is called by a consumer before it begins consumption using TokenStream.incrementToken().

Methods inherited from class org.apache.lucene.analysis.TokenFilter

close, end

Methods inherited from class org.apache.lucene.util.AttributeSource

addAttribute, addAttributeImpl, captureState, clearAttributes, cloneAttributes, copyTo, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, restoreState, toString

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

CommonGramsQueryFilter

public CommonGramsQueryFilter(CommonGramsFilter input)

Constructs a new CommonGramsQueryFilter based on the provided CommomGramsFilter

Parameters:

input - CommonGramsFilter the QueryFilter will use

Method Detail

reset

public void reset()
           throws IOException

This method is called by a consumer before it begins consumption using TokenStream.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 throw IllegalStateException 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 class TokenFilter

Throws:

IOException

incrementToken

public boolean incrementToken()
                       throws IOException

Output bigrams whenever possible to optimize queries. Only output unigrams when they are not a member of a bigram. Example:

• input: "the rain in spain falls mainly"
• output:"the-rain", "rain-in" ,"in-spain", "falls", "mainly"

Specified by:

incrementToken in class TokenStream

Returns:

false for end of stream; true otherwise

Throws:

IOException

isGramType

public boolean isGramType()

Convenience method to check if the current type is a gram type

Returns:

true if the current type is a gram type, false otherwise