org.apache.lucene.search

Class FuzzyLikeThisQuery

java.lang.Object

org.apache.lucene.search.Query

org.apache.lucene.search.FuzzyLikeThisQuery

All Implemented Interfaces:

Serializable, Cloneable

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.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
FuzzyLikeThisQuery(int maxNumTerms, Analyzer analyzer)

Method Summary

Methods

Modifier and Type	Method and Description
void	addTerms(String queryString, String fieldName, float minSimilarity, int prefixLength) Adds user input for "fuzzification"
boolean	equals(Object obj)
int	hashCode()
boolean	isIgnoreTF()
Query	rewrite(IndexReader reader) Expert: called to re-write queries into primitive queries.
void	setIgnoreTF(boolean ignoreTF)
String	toString(String field) Prints a query to a string, with field assumed to be the default field and omitted.

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

clone, combine, createWeight, extractTerms, getBoost, getSimilarity, mergeBooleanQueries, setBoost, toString, weight

Methods inherited from class java.lang.Object

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

analyzer -

Method Detail

hashCode

public int hashCode()

Overrides:

hashCode in class Query

equals

public boolean equals(Object obj)

Overrides:

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

fieldName -

minSimilarity - The minimum similarity of the term variants (see FuzzyTermEnum)

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

rewrite

public Query rewrite(IndexReader reader)
              throws IOException

Description copied from class: Query

Expert: called to re-write queries into primitive queries. For example, a PrefixQuery will be rewritten into a BooleanQuery that consists of TermQuerys.

Overrides:

rewrite in class Query

Throws:

IOException

toString

public String toString(String field)

Description copied from class: Query

Prints a query to a string, with field assumed to be the default field and omitted.

The representation used is one that is supposed to be readable by QueryParser. However, there are the following limitations:

• If the query was created by the parser, the printed representation may not be exactly what was parsed. For example, characters that need to be escaped will be represented without the required backslash.
• Some of the more complicated queries (e.g. span queries) don't have a representation that can be parsed by QueryParser.

Specified by:

toString in class Query

isIgnoreTF

public boolean isIgnoreTF()

setIgnoreTF

public void setIgnoreTF(boolean ignoreTF)