Package org.apache.lucene.sandbox.queries

Class FuzzyLikeThisQuery

java.lang.Object

org.apache.lucene.search.Query

org.apache.lucene.sandbox.queries.FuzzyLikeThisQuery

public class FuzzyLikeThisQuery
extends Query

Fuzzifies ALL terms provided as strings and then picks the best n differentiating terms. In effect this mixes the behaviour of FuzzyQuery and MoreLikeThis but with special consideration of fuzzy scoring factors. This generally produces good results for queries where users may provide details in a number of fields and have no knowledge of boolean query syntax and also want a degree of fuzzy matching and a fast query.

For each source term the fuzzy variants are held in a BooleanQuery with no coord factor (because we are not looking for matches on multiple variants in any one doc). Additionally, a specialized TermQuery is used for variants and does not use that variant term's IDF because this would favour rarer terms eg misspellings. Instead, all variants use the same IDF ranking (the one for the source query term) and this is factored into the variant's boost. If the source query term does not exist in the index the average IDF of the variants is used.

Constructor Summary

Constructors

Constructor	Description
FuzzyLikeThisQuery(int maxNumTerms, Analyzer analyzer)

Method Summary

Modifier and Type	Method	Description
void	addTerms(String queryString, String fieldName, float minSimilarity, int prefixLength)	Adds user input for "fuzzification"
boolean	equals(Object other)
int	hashCode()
boolean	isIgnoreTF()
Query	rewrite(IndexReader reader)
void	setIgnoreTF(boolean ignoreTF)
String	toString(String field)
void	visit(QueryVisitor visitor)

Methods inherited from class org.apache.lucene.search.Query

classHash, createWeight, sameClassAs, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

FuzzyLikeThisQuery

public FuzzyLikeThisQuery(int maxNumTerms,
                          Analyzer analyzer)

Parameters:

maxNumTerms - The total number of terms clauses that will appear once rewritten as a BooleanQuery

Method Detail

hashCode

public int hashCode()

Specified by:

hashCode in class Query

equals

public boolean equals(Object other)

Specified by:

equals in class Query

addTerms

public void addTerms(String queryString,
                     String fieldName,
                     float minSimilarity,
                     int prefixLength)

Adds user input for "fuzzification"

Parameters:

queryString - The string which will be parsed by the analyzer and for which fuzzy variants will be parsed

minSimilarity - The minimum similarity of the term variants; must be 0, 1 or 2 (see FuzzyTermsEnum)

prefixLength - Length of required common prefix on variant terms (see FuzzyTermsEnum)

visit

public void visit(QueryVisitor visitor)

Specified by:

visit in class Query

rewrite

public Query rewrite(IndexReader reader)
              throws IOException

Overrides:

rewrite in class Query

Throws:

IOException

toString

public String toString(String field)

Specified by:

toString in class Query

isIgnoreTF

public boolean isIgnoreTF()

setIgnoreTF

public void setIgnoreTF(boolean ignoreTF)