Class CombinedFieldQuery
- java.lang.Object
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- org.apache.lucene.search.Query
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- org.apache.lucene.sandbox.search.CombinedFieldQuery
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- All Implemented Interfaces:
Accountable
public final class CombinedFieldQuery extends Query implements Accountable
AQuery
that treats multiple fields as a single stream and scores terms as if you had indexed them as a single term in a single field.The query works as follows:
- Given a list of fields and weights, it pretends there is a synthetic combined field where all terms have been indexed. It computes new term and collection statistics for this combined field.
- It uses a disjunction iterator and
IndexSearcher.getSimilarity()
to score documents.
In order for a similarity to be compatible,
Similarity.computeNorm(org.apache.lucene.index.FieldInvertState)
must be additive: the norm of the combined field is the sum of norms for each individual field. The norms must also be encoded usingSmallFloat.intToByte4(int)
. These requirements hold for all similarities that compute norms the same way asSimilarityBase.computeNorm(org.apache.lucene.index.FieldInvertState)
, which includesBM25Similarity
andDFRSimilarity
. Per-field similarities are not supported.The query also requires that either all fields or no fields have norms enabled. Having only some fields with norms enabled can result in errors.
The scoring is based on BM25F's simple formula described in: http://www.staff.city.ac.uk/~sb317/papers/foundations_bm25_review.pdf. This query implements the same approach but allows other similarities besides
BM25Similarity
.- WARNING: This API is experimental and might change in incompatible ways in the next release.
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Nested Class Summary
Nested Classes Modifier and Type Class Description static class
CombinedFieldQuery.Builder
A builder forCombinedFieldQuery
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Field Summary
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Fields inherited from interface org.apache.lucene.util.Accountable
NULL_ACCOUNTABLE
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description Weight
createWeight(IndexSearcher searcher, ScoreMode scoreMode, float boost)
boolean
equals(Object o)
List<Term>
getTerms()
int
hashCode()
long
ramBytesUsed()
Query
rewrite(IndexSearcher indexSearcher)
String
toString(String field)
void
visit(QueryVisitor visitor)
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Methods inherited from class org.apache.lucene.search.Query
classHash, rewrite, sameClassAs, toString
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Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
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Methods inherited from interface org.apache.lucene.util.Accountable
getChildResources
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Method Detail
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ramBytesUsed
public long ramBytesUsed()
- Specified by:
ramBytesUsed
in interfaceAccountable
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rewrite
public Query rewrite(IndexSearcher indexSearcher) throws IOException
- Overrides:
rewrite
in classQuery
- Throws:
IOException
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visit
public void visit(QueryVisitor visitor)
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createWeight
public Weight createWeight(IndexSearcher searcher, ScoreMode scoreMode, float boost) throws IOException
- Overrides:
createWeight
in classQuery
- Throws:
IOException
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