Class FuzzyLikeThisQuery

  extended by
      extended by
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
FuzzyLikeThisQuery(int maxNumTerms, Analyzer analyzer)
Method Summary
 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
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


public FuzzyLikeThisQuery(int maxNumTerms,
                          Analyzer analyzer)
maxNumTerms - The total number of terms clauses that will appear once rewritten as a BooleanQuery
analyzer -
Method Detail


public int hashCode()
hashCode in class Query


public boolean equals(Object obj)
equals in class Query


public void addTerms(String queryString,
                     String fieldName,
                     float minSimilarity,
                     int prefixLength)
Adds user input for "fuzzification"

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)


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.

rewrite in class Query


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:

Specified by:
toString in class Query


public boolean isIgnoreTF()


public void setIgnoreTF(boolean ignoreTF)

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