org.apache.solr.analysis

Class ReversedWildcardFilterFactory

java.lang.Object

org.apache.lucene.analysis.util.AbstractAnalysisFactory

org.apache.lucene.analysis.util.TokenFilterFactory

org.apache.solr.analysis.ReversedWildcardFilterFactory

public class ReversedWildcardFilterFactory
extends TokenFilterFactory

Factory for ReversedWildcardFilter-s. When this factory is added to an analysis chain, it will be used both for filtering the tokens during indexing, and to determine the query processing of this field during search.

This class supports the following init arguments:

• withOriginal - if true, then produce both original and reversed tokens at the same positions. If false, then produce only reversed tokens.
• maxPosAsterisk - maximum position (1-based) of the asterisk wildcard ('*') that triggers the reversal of query term. Asterisk that occurs at positions higher than this value will not cause the reversal of query term. Defaults to 2, meaning that asterisks on positions 1 and 2 will cause a reversal.
• maxPosQuestion - maximum position (1-based) of the question mark wildcard ('?') that triggers the reversal of query term. Defaults to 1. Set this to 0, and maxPosAsterisk to 1 to reverse only pure suffix queries (i.e. ones with a single leading asterisk).
• maxFractionAsterisk - additional parameter that triggers the reversal if asterisk ('*') position is less than this fraction of the query token length. Defaults to 0.0f (disabled).
• minTrailing - minimum number of trailing characters in query token after the last wildcard character. For good performance this should be set to a value larger than 1. Defaults to 2.

Note 1: This filter always reverses input tokens during indexing. Note 2: Query tokens without wildcard characters will never be reversed.

 <fieldType name="text_rvswc" class="solr.TextField" positionIncrementGap="100">
   <analyzer type="index">
     <tokenizer class="solr.WhitespaceTokenizerFactory"/>
     <filter class="solr.ReversedWildcardFilterFactory" withOriginal="true"
             maxPosAsterisk="2" maxPosQuestion="1" minTrailing="2" maxFractionAsterisk="0"/>
   </analyzer>
   <analyzer type="query">
     <tokenizer class="solr.WhitespaceTokenizerFactory"/>
   </analyzer>
 </fieldType>

Field Summary

Fields inherited from class org.apache.lucene.analysis.util.AbstractAnalysisFactory

LUCENE_MATCH_VERSION_PARAM, luceneMatchVersion

Constructor Summary

Constructors

Constructor and Description
ReversedWildcardFilterFactory(Map<String,String> args) Creates a new ReversedWildcardFilterFactory

Method Summary

Modifier and Type	Method and Description
TokenStream	create(TokenStream input)
char	getMarkerChar()
boolean	shouldReverse(String token) This method encapsulates the logic that determines whether a query token should be reversed in order to use the reversed terms in the index.

Methods inherited from class org.apache.lucene.analysis.util.TokenFilterFactory

availableTokenFilters, forName, lookupClass, reloadTokenFilters

Methods inherited from class org.apache.lucene.analysis.util.AbstractAnalysisFactory

get, get, get, get, get, getBoolean, getChar, getClassArg, getFloat, getInt, getLines, getLuceneMatchVersion, getOriginalArgs, getPattern, getSet, getSnowballWordSet, getWordSet, isExplicitLuceneMatchVersion, require, require, require, requireBoolean, requireChar, requireFloat, requireInt, setExplicitLuceneMatchVersion, splitFileNames

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ReversedWildcardFilterFactory

public ReversedWildcardFilterFactory(Map<String,String> args)

Creates a new ReversedWildcardFilterFactory

Method Detail

create

public TokenStream create(TokenStream input)

Specified by:

create in class TokenFilterFactory

shouldReverse

public boolean shouldReverse(String token)

This method encapsulates the logic that determines whether a query token should be reversed in order to use the reversed terms in the index.

Parameters:

token - input token.

Returns:

true if input token should be reversed, false otherwise.

getMarkerChar

public char getMarkerChar()