Class MultiTermQuery
- java.lang.Object
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- org.apache.lucene.search.Query
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- org.apache.lucene.search.MultiTermQuery
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- Direct Known Subclasses:
AutomatonQuery
,FuzzyQuery
public abstract class MultiTermQuery extends Query
An abstractQuery
that matches documents containing a subset of terms provided by aFilteredTermsEnum
enumeration.This query cannot be used directly; you must subclass it and define
getTermsEnum(Terms,AttributeSource)
to provide aFilteredTermsEnum
that iterates through the terms to be matched.NOTE: if
setRewriteMethod(org.apache.lucene.search.MultiTermQuery.RewriteMethod)
is eitherCONSTANT_SCORE_BOOLEAN_REWRITE
orSCORING_BOOLEAN_REWRITE
, you may encounter aBooleanQuery.TooManyClauses
exception during searching, which happens when the number of terms to be searched exceedsBooleanQuery.getMaxClauseCount()
. SettingsetRewriteMethod(org.apache.lucene.search.MultiTermQuery.RewriteMethod)
toCONSTANT_SCORE_REWRITE
prevents this.The recommended rewrite method is
CONSTANT_SCORE_REWRITE
: it doesn't spend CPU computing unhelpful scores, and is the most performant rewrite method given the query. If you need scoring (likeFuzzyQuery
, useMultiTermQuery.TopTermsScoringBooleanQueryRewrite
which uses a priority queue to only collect competitive terms and not hit this limitation. Note that org.apache.lucene.queryparser.classic.QueryParser produces MultiTermQueries usingCONSTANT_SCORE_REWRITE
by default.
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Nested Class Summary
Nested Classes Modifier and Type Class Description static class
MultiTermQuery.RewriteMethod
Abstract class that defines how the query is rewritten.static class
MultiTermQuery.TopTermsBlendedFreqScoringRewrite
A rewrite method that first translates each term intoBooleanClause.Occur.SHOULD
clause in a BooleanQuery, but adjusts the frequencies used for scoring to be blended across the terms, otherwise the rarest term typically ranks highest (often not useful eg in the set of expanded terms in a FuzzyQuery).static class
MultiTermQuery.TopTermsBoostOnlyBooleanQueryRewrite
A rewrite method that first translates each term intoBooleanClause.Occur.SHOULD
clause in a BooleanQuery, but the scores are only computed as the boost.static class
MultiTermQuery.TopTermsScoringBooleanQueryRewrite
A rewrite method that first translates each term intoBooleanClause.Occur.SHOULD
clause in a BooleanQuery, and keeps the scores as computed by the query.
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Field Summary
Fields Modifier and Type Field Description static MultiTermQuery.RewriteMethod
CONSTANT_SCORE_BOOLEAN_REWRITE
LikeSCORING_BOOLEAN_REWRITE
except scores are not computed.static MultiTermQuery.RewriteMethod
CONSTANT_SCORE_REWRITE
A rewrite method that first creates a private Filter, by visiting each term in sequence and marking all docs for that term.protected String
field
protected MultiTermQuery.RewriteMethod
rewriteMethod
static MultiTermQuery.RewriteMethod
SCORING_BOOLEAN_REWRITE
A rewrite method that first translates each term intoBooleanClause.Occur.SHOULD
clause in a BooleanQuery, and keeps the scores as computed by the query.
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Constructor Summary
Constructors Constructor Description MultiTermQuery(String field)
Constructs a query matching terms that cannot be represented with a single Term.
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Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description boolean
equals(Object other)
Override and implement query instance equivalence properly in a subclass.String
getField()
Returns the field name for this queryMultiTermQuery.RewriteMethod
getRewriteMethod()
TermsEnum
getTermsEnum(Terms terms)
Constructs an enumeration that expands the pattern term.protected abstract TermsEnum
getTermsEnum(Terms terms, AttributeSource atts)
Construct the enumeration to be used, expanding the pattern term.int
hashCode()
Override and implement query hash code properly in a subclass.Query
rewrite(IndexReader reader)
To rewrite to a simpler form, instead return a simpler enum fromgetTermsEnum(Terms, AttributeSource)
.void
setRewriteMethod(MultiTermQuery.RewriteMethod method)
Sets the rewrite method to be used when executing the query.-
Methods inherited from class org.apache.lucene.search.Query
classHash, createWeight, sameClassAs, toString, toString, visit
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Field Detail
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field
protected final String field
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rewriteMethod
protected MultiTermQuery.RewriteMethod rewriteMethod
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CONSTANT_SCORE_REWRITE
public static final MultiTermQuery.RewriteMethod CONSTANT_SCORE_REWRITE
A rewrite method that first creates a private Filter, by visiting each term in sequence and marking all docs for that term. Matching documents are assigned a constant score equal to the query's boost.This method is faster than the BooleanQuery rewrite methods when the number of matched terms or matched documents is non-trivial. Also, it will never hit an errant
BooleanQuery.TooManyClauses
exception.
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SCORING_BOOLEAN_REWRITE
public static final MultiTermQuery.RewriteMethod SCORING_BOOLEAN_REWRITE
A rewrite method that first translates each term intoBooleanClause.Occur.SHOULD
clause in a BooleanQuery, and keeps the scores as computed by the query. Note that typically such scores are meaningless to the user, and require non-trivial CPU to compute, so it's almost always better to useCONSTANT_SCORE_REWRITE
instead.NOTE: This rewrite method will hit
BooleanQuery.TooManyClauses
if the number of terms exceedsBooleanQuery.getMaxClauseCount()
.
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CONSTANT_SCORE_BOOLEAN_REWRITE
public static final MultiTermQuery.RewriteMethod CONSTANT_SCORE_BOOLEAN_REWRITE
LikeSCORING_BOOLEAN_REWRITE
except scores are not computed. Instead, each matching document receives a constant score equal to the query's boost.NOTE: This rewrite method will hit
BooleanQuery.TooManyClauses
if the number of terms exceedsBooleanQuery.getMaxClauseCount()
.
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Constructor Detail
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MultiTermQuery
public MultiTermQuery(String field)
Constructs a query matching terms that cannot be represented with a single Term.
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Method Detail
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getField
public final String getField()
Returns the field name for this query
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getTermsEnum
protected abstract TermsEnum getTermsEnum(Terms terms, AttributeSource atts) throws IOException
Construct the enumeration to be used, expanding the pattern term. This method should only be called if the field exists (ie, implementations can assume the field does exist). This method should not return null (should instead returnTermsEnum.EMPTY
if no terms match). The TermsEnum must already be positioned to the first matching term. The givenAttributeSource
is passed by theMultiTermQuery.RewriteMethod
to share information between segments, for exampleTopTermsRewrite
uses it to share maximum competitive boosts- Throws:
IOException
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getTermsEnum
public final TermsEnum getTermsEnum(Terms terms) throws IOException
Constructs an enumeration that expands the pattern term. This method should only be called if the field exists (ie, implementations can assume the field does exist). This method never returns null. The returned TermsEnum is positioned to the first matching term.- Throws:
IOException
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rewrite
public final Query rewrite(IndexReader reader) throws IOException
To rewrite to a simpler form, instead return a simpler enum fromgetTermsEnum(Terms, AttributeSource)
. For example, to rewrite to a single term, return aSingleTermsEnum
- Overrides:
rewrite
in classQuery
- Throws:
IOException
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getRewriteMethod
public MultiTermQuery.RewriteMethod getRewriteMethod()
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setRewriteMethod
public void setRewriteMethod(MultiTermQuery.RewriteMethod method)
Sets the rewrite method to be used when executing the query. You can use one of the four core methods, or implement your own subclass ofMultiTermQuery.RewriteMethod
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hashCode
public int hashCode()
Description copied from class:Query
Override and implement query hash code properly in a subclass. This is required so thatQueryCache
works properly.- Specified by:
hashCode
in classQuery
- See Also:
Query.equals(Object)
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equals
public boolean equals(Object other)
Description copied from class:Query
Override and implement query instance equivalence properly in a subclass. This is required so thatQueryCache
works 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 that other instance. Utility methods are provided for certain repetitive code.- Specified by:
equals
in classQuery
- See Also:
Query.sameClassAs(Object)
,Query.classHash()
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