Package org.apache.lucene.queries

Class BlendedTermQuery

  • public abstract class BlendedTermQuery
extends org.apache.lucene.search.Query
    BlendedTermQuery can be used to unify term statistics across one or more fields in the index. A common problem with structured documents is that a term that is significant in on field might not be significant in other fields like in a scenario where documents represent users with a "first_name" and a "second_name". When someone searches for "simon" it will very likely get "paul simon" first since "simon" is a an uncommon last name ie. has a low document frequency. This query tries to "lie" about the global statistics like document frequency as well total term frequency to rank based on the estimated statistics.

    While aggregating the total term frequency is trivial since it can be summed up not every Similarity makes use of this statistic. The document frequency which is used in the ClassicSimilarity can only be estimated as an lower-bound since it is a document based statistic. For the document frequency the maximum frequency across all fields per term is used which is the minimum number of documents the terms occurs in.

    • Constructor Summary

      Constructors 
      Constructor Description
      BlendedTermQuery​(org.apache.lucene.index.Term[] terms, float[] boosts)  

    • Method Summary

      Modifier and Type Method Description
      protected void blend​(org.apache.lucene.index.TermStates[] contexts, int maxDoc, org.apache.lucene.index.IndexReader reader)  
      static BlendedTermQuery commonTermsBlendedQuery​(org.apache.lucene.index.Term[] terms, float[] boosts, float maxTermFrequency)  
      static BlendedTermQuery dismaxBlendedQuery​(org.apache.lucene.index.Term[] terms, float tieBreakerMultiplier)  
      static BlendedTermQuery dismaxBlendedQuery​(org.apache.lucene.index.Term[] terms, float[] boosts, float tieBreakerMultiplier)  
      boolean equals​(java.lang.Object o)  
      java.util.List<org.apache.lucene.index.Term> getTerms()  
      int hashCode()  
      org.apache.lucene.search.Query rewrite​(org.apache.lucene.index.IndexReader reader)  
      protected abstract org.apache.lucene.search.Query topLevelQuery​(org.apache.lucene.index.Term[] terms, org.apache.lucene.index.TermStates[] ctx, int[] docFreqs, int maxDoc)  
      java.lang.String toString​(java.lang.String field)  

      • 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

      • BlendedTermQuery

        public BlendedTermQuery​(org.apache.lucene.index.Term[] terms,
                        float[] boosts)

    • Method Detail

      • rewrite

        public org.apache.lucene.search.Query rewrite​(org.apache.lucene.index.IndexReader reader)
                                       throws java.io.IOException
        Overrides:
        rewrite in class org.apache.lucene.search.Query
        Throws:
        java.io.IOException

      • topLevelQuery

        protected abstract org.apache.lucene.search.Query topLevelQuery​(org.apache.lucene.index.Term[] terms,
                                                                org.apache.lucene.index.TermStates[] ctx,
                                                                int[] docFreqs,
                                                                int maxDoc)

      • blend

        protected void blend​(org.apache.lucene.index.TermStates[] contexts,
                     int maxDoc,
                     org.apache.lucene.index.IndexReader reader)
              throws java.io.IOException
        Throws:
        java.io.IOException

      • getTerms

        public java.util.List<org.apache.lucene.index.Term> getTerms()

      • toString

        public java.lang.String toString​(java.lang.String field)
        Specified by:
        toString in class org.apache.lucene.search.Query

      • equals

        public boolean equals​(java.lang.Object o)
        Specified by:
        equals in class org.apache.lucene.search.Query

      • hashCode

        public int hashCode()
        Specified by:
        hashCode in class org.apache.lucene.search.Query

      • commonTermsBlendedQuery

        public static BlendedTermQuery commonTermsBlendedQuery​(org.apache.lucene.index.Term[] terms,
                                                       float[] boosts,
                                                       float maxTermFrequency)

      • dismaxBlendedQuery

        public static BlendedTermQuery dismaxBlendedQuery​(org.apache.lucene.index.Term[] terms,
                                                  float tieBreakerMultiplier)

      • dismaxBlendedQuery

        public static BlendedTermQuery dismaxBlendedQuery​(org.apache.lucene.index.Term[] terms,
                                                  float[] boosts,
                                                  float tieBreakerMultiplier)