Package org.apache.lucene.search

Class Scorer

java.lang.Object

org.apache.lucene.search.DocIdSetIterator

org.apache.lucene.index.DocsEnum

org.apache.lucene.search.Scorer

Direct Known Subclasses:

ConstantScoreQuery.ConstantScorer, ScoreCachingWrappingScorer, SpanScorer

public abstract class Scorer
extends DocsEnum

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	Description
static class	Scorer.ChildScorer	A child Scorer and its relationship to its parent.

Field Summary

Fields

Modifier and Type	Field	Description
protected Weight	weight	the Scorer's parent Weight.

Fields inherited from class org.apache.lucene.index.DocsEnum

FLAG_FREQS, FLAG_NONE

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

NO_MORE_DOCS

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	Scorer(Weight weight)	Constructs a Scorer

Method Summary

Modifier and Type	Method	Description
Collection<Scorer.ChildScorer>	getChildren()	Returns child sub-scorers
Weight	getWeight()	returns parent Weight
abstract float	score()	Returns the score of the current document matching the query.
void	score(Collector collector)	Scores and collects all matching documents.
boolean	score(Collector collector, int max, int firstDocID)	Expert: Collects matching documents in a range.

Methods inherited from class org.apache.lucene.index.DocsEnum

attributes, freq

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

advance, cost, docID, empty, nextDoc, slowAdvance

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

the Scorer's parent Weight. in some cases this may be null

Constructor Detail

Scorer

protected Scorer(Weight weight)

Constructs a Scorer

Parameters:

weight - The scorers Weight.

Method Detail

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

public 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.

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

getWeight

public Weight getWeight()

returns parent Weight

getChildren

public Collection<Scorer.ChildScorer> getChildren()

Returns child sub-scorers