Class MultiTermQuery

An abstract Query that matches documents containing a subset of terms provided by a FilteredTermsEnum enumeration.

This query cannot be used directly; you must subclass it and define GetTermsEnum(Terms, AttributeSource) to provide a FilteredTermsEnum that iterates through the terms to be matched.

NOTE: if MultiTermRewriteMethod is either CONSTANT_SCORE_BOOLEAN_QUERY_REWRITE or SCORING_BOOLEAN_QUERY_REWRITE, you may encounter a BooleanQuery.TooManyClausesException exception during searching, which happens when the number of terms to be searched exceeds MaxClauseCount. Setting MultiTermRewriteMethod to CONSTANT_SCORE_FILTER_REWRITE prevents this.

The recommended rewrite method is CONSTANT_SCORE_AUTO_REWRITE_DEFAULT: it doesn't spend CPU computing unhelpful scores, and it tries to pick the most performant rewrite method given the query. If you need scoring (like , use MultiTermQuery.TopTermsScoringBooleanQueryRewrite which uses a priority queue to only collect competitive terms and not hit this limitation.

Note that QueryParsers.Classic.QueryParser produces MultiTermQuerys using CONSTANT_SCORE_AUTO_REWRITE_DEFAULT by default.

Inheritance

System.Object

Query

MultiTermQuery

AutomatonQuery

FuzzyQuery

NumericRangeQuery<T>

PrefixQuery

TermRangeQuery

Inherited Members

Query.Boost

Query.ToString(String)

Query.ToString()

Query.CreateWeight(IndexSearcher)

Query.ExtractTerms(ISet<Term>)

Query.Clone()

Namespace: Lucene.Net.Search

Assembly: Lucene.Net.dll

Syntax

public abstract class MultiTermQuery : Query

Constructors

MultiTermQuery(String)

Constructs a query matching terms that cannot be represented with a single Term.

Declaration

public MultiTermQuery(string field)

Parameters

Type	Name	Description
System.String	field

Fields

CONSTANT_SCORE_AUTO_REWRITE_DEFAULT

Read-only default instance of ConstantScoreAutoRewrite, with TermCountCutoff set to DEFAULT_TERM_COUNT_CUTOFF and DocCountPercent set to DEFAULT_DOC_COUNT_PERCENT. Note that you cannot alter the configuration of this instance; you'll need to create a private instance instead.

Declaration

public static readonly MultiTermQuery.RewriteMethod CONSTANT_SCORE_AUTO_REWRITE_DEFAULT

Field Value

Type	Description
MultiTermQuery.RewriteMethod

CONSTANT_SCORE_BOOLEAN_QUERY_REWRITE

Like SCORING_BOOLEAN_QUERY_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.TooManyClausesException if the number of terms exceeds MaxClauseCount.

Declaration

public static readonly MultiTermQuery.RewriteMethod CONSTANT_SCORE_BOOLEAN_QUERY_REWRITE

Field Value

Type	Description
MultiTermQuery.RewriteMethod

See Also

MultiTermRewriteMethod

CONSTANT_SCORE_FILTER_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.TooManyClausesException exception.

Declaration

public static readonly MultiTermQuery.RewriteMethod CONSTANT_SCORE_FILTER_REWRITE

Field Value

Type	Description
MultiTermQuery.RewriteMethod

See Also

MultiTermRewriteMethod

m_field

Declaration

protected readonly string m_field

Field Value

Type	Description
System.String

m_rewriteMethod

Declaration

protected MultiTermQuery.RewriteMethod m_rewriteMethod

Field Value

Type	Description
MultiTermQuery.RewriteMethod

SCORING_BOOLEAN_QUERY_REWRITE

A rewrite method that first translates each term into 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 use CONSTANT_SCORE_AUTO_REWRITE_DEFAULT instead.

NOTE: this rewrite method will hit BooleanQuery.TooManyClausesException if the number of terms exceeds MaxClauseCount.

Declaration

public static readonly MultiTermQuery.RewriteMethod SCORING_BOOLEAN_QUERY_REWRITE

Field Value

Type	Description
MultiTermQuery.RewriteMethod

See Also

MultiTermRewriteMethod

Properties

Field

Returns the field name for this query

Declaration

public string Field { get; }

Property Value

Type	Description
System.String

MultiTermRewriteMethod

Gets or 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 of MultiTermQuery.RewriteMethod.

Declaration

public virtual MultiTermQuery.RewriteMethod MultiTermRewriteMethod { get; set; }

Property Value

Type	Description
MultiTermQuery.RewriteMethod

Methods

Equals(Object)

Declaration

public override bool Equals(object obj)

Parameters

Type	Name	Description
System.Object	obj

Returns

Type	Description
System.Boolean

Overrides

Query.Equals(Object)

GetHashCode()

Declaration

public override int GetHashCode()

Returns

Type	Description
System.Int32

Overrides

Query.GetHashCode()

GetTermsEnum(Terms)

Convenience method, if no attributes are needed: this simply passes empty attributes and is equal to:

GetTermsEnum(terms, new AttributeSource())

Declaration

public TermsEnum GetTermsEnum(Terms terms)

Parameters

Type	Name	Description
Terms	terms

Returns

Type	Description
TermsEnum

GetTermsEnum(Terms, AttributeSource)

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 return EMPTY if no terms match). The TermsEnum must already be positioned to the first matching term. The given AttributeSource is passed by the MultiTermQuery.RewriteMethod to provide attributes, the rewrite method uses to inform about e.g. maximum competitive boosts. this is currently only used by TopTermsRewrite<Q>.

Declaration

protected abstract TermsEnum GetTermsEnum(Terms terms, AttributeSource atts)

Parameters

Type	Name	Description
Terms	terms
AttributeSource	atts

Returns

Type	Description
TermsEnum

Rewrite(IndexReader)

To rewrite to a simpler form, instead return a simpler enum from GetTermsEnum(Terms, AttributeSource). For example, to rewrite to a single term, return a SingleTermsEnum.

Declaration

public override sealed Query Rewrite(IndexReader reader)

Parameters

Type	Name	Description
IndexReader	reader

Returns

Type	Description
Query

Overrides

Query.Rewrite(IndexReader)