Package org.apache.lucene.queries

Class BlendedTermQuery

java.lang.Object

org.apache.lucene.search.Query

org.apache.lucene.queries.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.TermContext[] 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.TermContext[] ctx, int[] docFreqs, int maxDoc)
java.lang.String	toString(java.lang.String field)

Methods inherited from class java.lang.Object

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

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

classHash, createWeight, sameClassAs, toString

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.TermContext[] ctx,
                                                                int[] docFreqs,
                                                                int maxDoc)

blend

protected void blend(org.apache.lucene.index.TermContext[] 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)