org.apache.lucene.sandbox.queries

Class 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 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

      • equals

        public boolean equals(Object other)
        Description copied from class: Query
        Override and implement query instance equivalence properly in a subclass. This is required so that QueryCache works properly. Typically a query will be equal to another only if it's an instance of the same class and its document-filtering properties are identical that other instance. Utility methods are provided for certain repetitive code.
        Specified by:
        equals in class Query
        See Also:
        Query.sameClassAs(Object), Query.classHash()
      • 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 (see FuzzyTermsEnum)
        prefixLength - Length of required common prefix on variant terms (see FuzzyTermsEnum)
      • 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.
        Specified by:
        toString in class Query
      • setIgnoreTF

        public void setIgnoreTF(boolean ignoreTF)