public abstract class

MultiTermQuery

extends Query
java.lang.Object
   ↳ org.apache.lucene.search.Query
     ↳ org.apache.lucene.search.MultiTermQuery
Known Direct Subclasses

Class Overview

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

This query cannot be used directly; you must subclass it and define getEnum(IndexReader) to provide a FilteredTermEnum that iterates through the terms to be matched.

NOTE: if setRewriteMethod(MultiTermQuery.RewriteMethod) is either CONSTANT_SCORE_BOOLEAN_QUERY_REWRITE or SCORING_BOOLEAN_QUERY_REWRITE, you may encounter a BooleanQuery.TooManyClauses exception during searching, which happens when the number of terms to be searched exceeds getMaxClauseCount(). Setting setRewriteMethod(MultiTermQuery.RewriteMethod) 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. Note that QueryParser produces MultiTermQueries using CONSTANT_SCORE_AUTO_REWRITE_DEFAULT by default.

Summary

Nested Classes
class MultiTermQuery.ConstantScoreAutoRewrite A rewrite method that tries to pick the best constant-score rewrite method based on term and document counts from the query. 
class MultiTermQuery.RewriteMethod Abstract class that defines how the query is rewritten. 
Fields
public static final MultiTermQuery.RewriteMethod CONSTANT_SCORE_AUTO_REWRITE_DEFAULT Read-only default instance of MultiTermQuery.ConstantScoreAutoRewrite, with setTermCountCutoff(int) set to DEFAULT_TERM_COUNT_CUTOFF and setDocCountPercent(double) set to DEFAULT_DOC_COUNT_PERCENT.
public static final MultiTermQuery.RewriteMethod CONSTANT_SCORE_BOOLEAN_QUERY_REWRITE Like SCORING_BOOLEAN_QUERY_REWRITE except scores are not computed.
public static final MultiTermQuery.RewriteMethod 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.
public static final 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.
protected MultiTermQuery.RewriteMethod rewriteMethod
Public Constructors
MultiTermQuery()
Constructs a query matching terms that cannot be represented with a single Term.
Public Methods
void clearTotalNumberOfTerms()
Expert: Resets the counting of unique terms.
boolean equals(Object obj)
MultiTermQuery.RewriteMethod getRewriteMethod()
int getTotalNumberOfTerms()
Expert: Return the number of unique terms visited during execution of the query.
int hashCode()
Query rewrite(IndexReader reader)
Expert: called to re-write queries into primitive queries.
void setRewriteMethod(MultiTermQuery.RewriteMethod method)
Sets the rewrite method to be used when executing the query.
Protected Methods
abstract FilteredTermEnum getEnum(IndexReader reader)
Construct the enumeration to be used, expanding the pattern term.
void incTotalNumberOfTerms(int inc)
[Expand]
Inherited Methods
From class org.apache.lucene.search.Query
From class java.lang.Object

Fields

public static final MultiTermQuery.RewriteMethod CONSTANT_SCORE_AUTO_REWRITE_DEFAULT

Read-only default instance of MultiTermQuery.ConstantScoreAutoRewrite, with setTermCountCutoff(int) set to DEFAULT_TERM_COUNT_CUTOFF and setDocCountPercent(double) 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.

public static final 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.TooManyClauses if the number of terms exceeds getMaxClauseCount().

See Also

public static final MultiTermQuery.RewriteMethod 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.TooManyClauses exception.

See Also

public static final 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.TooManyClauses if the number of terms exceeds getMaxClauseCount().

See Also

protected MultiTermQuery.RewriteMethod rewriteMethod

Public Constructors

public MultiTermQuery ()

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

Public Methods

public void clearTotalNumberOfTerms ()

Expert: Resets the counting of unique terms. Do this before executing the query/filter.

See Also

public boolean equals (Object obj)

public MultiTermQuery.RewriteMethod getRewriteMethod ()

See Also

public int getTotalNumberOfTerms ()

Expert: Return the number of unique terms visited during execution of the query. If there are many of them, you may consider using another query type or optimize your total term count in index.

This method is not thread safe, be sure to only call it when no query is running! If you re-use the same query instance for another search, be sure to first reset the term counter with clearTotalNumberOfTerms().

On optimized indexes / no MultiReaders, you get the correct number of unique terms for the whole index. Use this number to compare different queries. For non-optimized indexes this number can also be achieved in non-constant-score mode. In constant-score mode you get the total number of terms seeked for all segments / sub-readers.

See Also

public int hashCode ()

public Query rewrite (IndexReader reader)

Expert: called to re-write queries into primitive queries. For example, a PrefixQuery will be rewritten into a BooleanQuery that consists of TermQuerys.

Throws
IOException

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 of MultiTermQuery.RewriteMethod.

Protected Methods

protected abstract FilteredTermEnum getEnum (IndexReader reader)

Construct the enumeration to be used, expanding the pattern term.

Throws
IOException

protected void incTotalNumberOfTerms (int inc)