Class CombinedFieldQuery
- All Implemented Interfaces:
Accountable
Query
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 using SmallFloat.intToByte4(int)
. These requirements hold for all similarities that
compute norms the same way as SimilarityBase.computeNorm(org.apache.lucene.index.FieldInvertState)
, which includes BM25Similarity
and DFRSimilarity
. 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.
-
Nested Class Summary
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Field Summary
Fields inherited from interface org.apache.lucene.util.Accountable
NULL_ACCOUNTABLE
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Method Summary
Modifier and TypeMethodDescriptioncreateWeight
(IndexSearcher searcher, ScoreMode scoreMode, float boost) boolean
getTerms()
int
hashCode()
long
rewrite
(IndexReader reader) void
visit
(QueryVisitor visitor) Methods inherited from class org.apache.lucene.search.Query
classHash, sameClassAs, toString
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
Methods inherited from interface org.apache.lucene.util.Accountable
getChildResources
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Method Details
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getTerms
-
toString
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equals
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hashCode
public int hashCode() -
ramBytesUsed
public long ramBytesUsed()- Specified by:
ramBytesUsed
in interfaceAccountable
-
rewrite
- Overrides:
rewrite
in classQuery
- Throws:
IOException
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visit
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createWeight
public Weight createWeight(IndexSearcher searcher, ScoreMode scoreMode, float boost) throws IOException - Overrides:
createWeight
in classQuery
- Throws:
IOException
-