Package org.apache.lucene.search

Class ScoringRewrite<Q extends Query>

java.lang.Object

org.apache.lucene.search.MultiTermQuery.RewriteMethod

org.apache.lucene.search.ScoringRewrite<Q>

public abstract class ScoringRewrite<Q extends Query>
extends MultiTermQuery.RewriteMethod

Base rewrite method that translates each term into a query, and keeps the scores as computed by the query.

Field Summary

Fields

Modifier and Type	Field	Description
static MultiTermQuery.RewriteMethod	CONSTANT_SCORE_BOOLEAN_QUERY_REWRITE	Like SCORING_BOOLEAN_QUERY_REWRITE except scores are not computed.
static ScoringRewrite<BooleanQuery>	SCORING_BOOLEAN_QUERY_REWRITE	A rewrite method that first translates each term into BooleanClause.Occur.SHOULD clause in a BooleanQuery, and keeps the scores as computed by the query.

Constructor Summary

Constructors

Constructor	Description
ScoringRewrite()

Method Summary

Modifier and Type	Method	Description
protected void	addClause(Q topLevel, Term term, int docCount, float boost)	Add a MultiTermQuery term to the top-level query
protected abstract void	addClause(Q topLevel, Term term, int docCount, float boost, TermContext states)
protected abstract void	checkMaxClauseCount(int count)	This method is called after every new term to check if the number of max clauses (e.g.
protected abstract Q	getTopLevelQuery()	Return a suitable top-level Query for holding all expanded terms.
Q	rewrite(IndexReader reader, MultiTermQuery query)

Methods inherited from class org.apache.lucene.search.MultiTermQuery.RewriteMethod

getTermsEnum

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

SCORING_BOOLEAN_QUERY_REWRITE

public static final ScoringRewrite<BooleanQuery> SCORING_BOOLEAN_QUERY_REWRITE

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

NOTE: This rewrite method will hit BooleanQuery.TooManyClauses if the number of terms exceeds BooleanQuery.getMaxClauseCount().

See Also:

MultiTermQuery.setRewriteMethod(org.apache.lucene.search.MultiTermQuery.RewriteMethod)

CONSTANT_SCORE_BOOLEAN_QUERY_REWRITE

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 BooleanQuery.getMaxClauseCount().

See Also:

MultiTermQuery.setRewriteMethod(org.apache.lucene.search.MultiTermQuery.RewriteMethod)

Constructor Detail

ScoringRewrite

public ScoringRewrite()

Method Detail

checkMaxClauseCount

protected abstract void checkMaxClauseCount(int count)
                                     throws IOException

This method is called after every new term to check if the number of max clauses (e.g. in BooleanQuery) is not exceeded. Throws the corresponding RuntimeException.

Throws:

IOException

rewrite

public final Q rewrite(IndexReader reader,
                       MultiTermQuery query)
                throws IOException

Specified by:

rewrite in class MultiTermQuery.RewriteMethod

Throws:

IOException

getTopLevelQuery

protected abstract Q getTopLevelQuery()
                               throws IOException

Return a suitable top-level Query for holding all expanded terms.

Throws:

IOException

addClause

protected final void addClause(Q topLevel,
                               Term term,
                               int docCount,
                               float boost)
                        throws IOException

Add a MultiTermQuery term to the top-level query

Throws:

IOException

addClause

protected abstract void addClause(Q topLevel,
                                  Term term,
                                  int docCount,
                                  float boost,
                                  TermContext states)
                           throws IOException

Throws:

IOException