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

args, luceneMatchVersion

Constructor Summary

ReversedWildcardFilterFactory()

Method Summary

TokenStream	create(TokenStream input)
protected float	getFloat(String name, float defValue)
char	getMarkerChar()
void	init(Map<String,String> args)
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

assureMatchVersion, getArgs, getBoolean, getBoolean, getInt, getInt, getInt, getLines, getLuceneMatchVersion, getOriginalArgs, getPattern, getSnowballWordSet, getWordSet, setLuceneMatchVersion, splitFileNames

Methods inherited from class java.lang.Object

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

Constructor Detail

ReversedWildcardFilterFactory

public ReversedWildcardFilterFactory()

Method Detail

init

public void init(Map<String,String> args)

Overrides:

init in class AbstractAnalysisFactory

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()

getFloat

protected float getFloat(String name,
                         float defValue)