Class BlendedTermQuery
- java.lang.Object
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- org.apache.lucene.search.Query
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- org.apache.lucene.search.BlendedTermQuery
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public final class BlendedTermQuery extends Query
AQuerythat blends index statistics across multiple terms. This is particularly useful when several terms should produce identical scores, regardless of their index statistics.For instance imagine that you are resolving synonyms at search time, all terms should produce identical scores instead of the default behavior, which tends to give higher scores to rare terms.
An other useful use-case is cross-field search: imagine that you would like to search for
johnon two fields:first_nameandlast_name. You might not want to give a higher weight to matches on the field wherejohnis rarer, in which caseBlendedTermQuerywould help as well.- 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 classBlendedTermQuery.BuilderA Builder forBlendedTermQuery.static classBlendedTermQuery.DisjunctionMaxRewriteABlendedTermQuery.RewriteMethodthat creates aDisjunctionMaxQueryout of the sub queries.static classBlendedTermQuery.RewriteMethodABlendedTermQuery.RewriteMethoddefines how queries for individual terms should be merged.
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Field Summary
Fields Modifier and Type Field Description static BlendedTermQuery.RewriteMethodBOOLEAN_REWRITEABlendedTermQuery.RewriteMethodthat adds all sub queries to aBooleanQuery.static BlendedTermQuery.RewriteMethodDISJUNCTION_MAX_REWRITEBlendedTermQuery.DisjunctionMaxRewriteinstance with a tie-breaker of0.01.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description booleanequals(Object other)Override and implement query instance equivalence properly in a subclass.inthashCode()Override and implement query hash code properly in a subclass.Queryrewrite(IndexSearcher indexSearcher)Expert: called to re-write queries into primitive queries.StringtoString(String field)Prints a query to a string, withfieldassumed to be the default field and omitted.voidvisit(QueryVisitor visitor)Recurse through the query tree, visiting any child queries.-
Methods inherited from class org.apache.lucene.search.Query
classHash, createWeight, rewrite, sameClassAs, toString
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Field Detail
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BOOLEAN_REWRITE
public static final BlendedTermQuery.RewriteMethod BOOLEAN_REWRITE
ABlendedTermQuery.RewriteMethodthat adds all sub queries to aBooleanQuery. ThisBlendedTermQuery.RewriteMethodis useful when matching on several fields is considered better than having a good match on a single field.
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DISJUNCTION_MAX_REWRITE
public static final BlendedTermQuery.RewriteMethod DISJUNCTION_MAX_REWRITE
BlendedTermQuery.DisjunctionMaxRewriteinstance with a tie-breaker of0.01.
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Method Detail
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equals
public boolean equals(Object other)
Description copied from class:QueryOverride and implement query instance equivalence properly in a subclass. This is required so thatQueryCacheworks 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 to those of the other instance. Utility methods are provided for certain repetitive code.
- Specified by:
equalsin classQuery- See Also:
Query.sameClassAs(Object),Query.classHash()
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hashCode
public int hashCode()
Description copied from class:QueryOverride and implement query hash code properly in a subclass. This is required so thatQueryCacheworks properly.- Specified by:
hashCodein classQuery- See Also:
Query.equals(Object)
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toString
public String toString(String field)
Description copied from class:QueryPrints a query to a string, withfieldassumed to be the default field and omitted.
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rewrite
public final Query rewrite(IndexSearcher indexSearcher) throws IOException
Description copied from class:QueryExpert: called to re-write queries into primitive queries. For example, a PrefixQuery will be rewritten into a BooleanQuery that consists of TermQuerys.Callers are expected to call
rewritemultiple times if necessary, until the rewritten query is the same as the original query.The rewrite process may be able to make use of IndexSearcher's executor and be executed in parallel if the executor is provided.
However, if any of the intermediary queries do not satisfy the new API, parallel rewrite is not possible for any subsequent sub-queries. To take advantage of this API, the entire query tree must override this method.
- Overrides:
rewritein classQuery- Throws:
IOException- See Also:
IndexSearcher.rewrite(Query)
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visit
public void visit(QueryVisitor visitor)
Description copied from class:QueryRecurse through the query tree, visiting any child queries.
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