org.apache.lucene.search

Class Scorer

java.lang.Object

org.apache.lucene.search.DocIdSetIterator

org.apache.lucene.search.Scorer

Direct Known Subclasses:

ConstantScoreQuery.ConstantScorer, ScoreCachingWrappingScorer, SpanScorer

public abstract class Scorer
extends DocIdSetIterator

Expert: Common scoring functionality for different types of queries.

A Scorer iterates over documents matching a query in increasing order of doc Id.

Document scores are computed using a given Similarity implementation.

NOTE: The values Float.Nan, Float.NEGATIVE_INFINITY and Float.POSITIVE_INFINITY are not valid scores. Certain collectors (eg TopScoreDocCollector) will not properly collect hits with these scores.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Scorer.ScorerVisitor<P extends Query,C extends Query,S extends Scorer> A callback to gather information from a scorer and its sub-scorers.

Field Summary

Fields

Modifier and Type	Field and Description
protected Weight	weight

Fields inherited from class org.apache.lucene.search.DocIdSetIterator

NO_MORE_DOCS

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	Scorer(Similarity similarity) Deprecated. Use Scorer(Weight) instead.
protected	Scorer(Similarity similarity, Weight weight) Deprecated. Use Scorer(Weight) instead.
protected	Scorer(Weight weight) Constructs a Scorer

Method Summary

Methods

Modifier and Type	Method and Description
float	freq() Returns number of matches for the current document.
Similarity	getSimilarity() Deprecated. Store any Similarity you might need privately in your implementation instead.
abstract float	score() Returns the score of the current document matching the query.
void	score(Collector collector) Scores and collects all matching documents.
protected boolean	score(Collector collector, int max, int firstDocID) Expert: Collects matching documents in a range.
void	visitScorers(Scorer.ScorerVisitor<Query,Query,Scorer> visitor) Expert: call this to gather details for all sub-scorers for this query.
void	visitSubScorers(Query parent, BooleanClause.Occur relationship, Scorer.ScorerVisitor<Query,Query,Scorer> visitor) Scorer subclasses should implement this method if the subclass itself contains multiple scorers to support gathering details for sub-scorers via Scorer.ScorerVisitor Note: this method will throw UnsupportedOperationException if no associated Weight instance is provided to Scorer(Weight)

Methods inherited from class org.apache.lucene.search.DocIdSetIterator

advance, docID, nextDoc

Methods inherited from class java.lang.Object

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

Field Detail

weight

protected final Weight weight

Constructor Detail

Scorer

protected Scorer(Weight weight)

Constructs a Scorer

Parameters:

weight - The scorers Weight.

Scorer

@Deprecated
protected Scorer(Similarity similarity)

Deprecated. Use Scorer(Weight) instead.

Constructs a Scorer.

Parameters:

similarity - The Similarity implementation used by this scorer.

Scorer

@Deprecated
protected Scorer(Similarity similarity,
                 Weight weight)

Deprecated. Use Scorer(Weight) instead.

Constructs a Scorer

Parameters:

similarity - The Similarity implementation used by this scorer.

weight - The scorers Weight

Method Detail

getSimilarity

@Deprecated
public Similarity getSimilarity()

Deprecated. Store any Similarity you might need privately in your implementation instead.

Returns the Similarity implementation used by this scorer.

score

public void score(Collector collector)
           throws IOException

Scores and collects all matching documents.

Parameters:

collector - The collector to which all matching documents are passed.

Throws:

IOException

score

protected boolean score(Collector collector,
            int max,
            int firstDocID)
                 throws IOException

Expert: Collects matching documents in a range. Hook for optimization. Note, firstDocID is added to ensure that DocIdSetIterator.nextDoc() was called before this method.

NOTE: Because of backwards compatibility, this method is still declared as protected, but it is intended to be public, because it's called from other classes (like BooleanScorer). If you subclass Scorer, you should declare the overridden method as public to ease transition to Lucene 4.0, where it will be public.

Parameters:

collector - The collector to which all matching documents are passed.

max - Do not score documents past this.

firstDocID - The first document ID (ensures DocIdSetIterator.nextDoc() is called before this method.

Returns:

true if more matching documents may remain.

Throws:

IOException

score

public abstract float score()
                     throws IOException

Returns the score of the current document matching the query. Initially invalid, until DocIdSetIterator.nextDoc() or DocIdSetIterator.advance(int) is called the first time, or when called from within Collector.collect(int).

Throws:

IOException

freq

public float freq()
           throws IOException

Returns number of matches for the current document. This returns a float (not int) because SloppyPhraseScorer discounts its freq according to how "sloppy" the match was.

Throws:

IOException

WARNING: This API is experimental and might change in incompatible ways in the next release.

visitScorers

public void visitScorers(Scorer.ScorerVisitor<Query,Query,Scorer> visitor)

Expert: call this to gather details for all sub-scorers for this query. This can be used, in conjunction with a custom Collector to gather details about how each sub-query matched the current hit.

Parameters:

visitor - a callback executed for each sub-scorer

WARNING: This API is experimental and might change in incompatible ways in the next release.

visitSubScorers

public void visitSubScorers(Query parent,
                   BooleanClause.Occur relationship,
                   Scorer.ScorerVisitor<Query,Query,Scorer> visitor)

Scorer subclasses should implement this method if the subclass itself contains multiple scorers to support gathering details for sub-scorers via Scorer.ScorerVisitor

Note: this method will throw UnsupportedOperationException if no associated Weight instance is provided to Scorer(Weight)

WARNING: This API is experimental and might change in incompatible ways in the next release.