Package org.apache.lucene.search

Class Scorer

java.lang.Object

org.apache.lucene.search.Scorer

Direct Known Subclasses:

ConstantScoreScorer, FilterScorer, SpanScorer

public abstract class Scorer
extends Object

Expert: Common scoring functionality for different types of queries.

A Scorer exposes an iterator() 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.

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method	Description
abstract int	docID()	Returns the doc ID that is currently being scored.
Collection<Scorer.ChildScorer>	getChildren()	Returns child sub-scorers positioned on the current document Note that this method should not be called on Scorers passed to LeafCollector.setScorer(Scorer), as these may be synthetic Scorers produced by BulkScorer which will throw an Exception.
Weight	getWeight()	returns parent Weight
abstract DocIdSetIterator	iterator()	Return a DocIdSetIterator over matching documents.
abstract float	score()	Returns the score of the current document matching the query.
TwoPhaseIterator	twoPhaseIterator()	Optional method: Return a TwoPhaseIterator view of this Scorer.

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

docID

public abstract int docID()

Returns the doc ID that is currently being scored. This will return -1 if the iterator() is not positioned or DocIdSetIterator.NO_MORE_DOCS if it has been entirely consumed.

See Also:

DocIdSetIterator.docID()

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 on the iterator() the first time, or when called from within LeafCollector.collect(int).

Throws:

IOException

getWeight

public Weight getWeight()

returns parent Weight

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

getChildren

public Collection<Scorer.ChildScorer> getChildren()
                                           throws IOException

Returns child sub-scorers positioned on the current document Note that this method should not be called on Scorers passed to LeafCollector.setScorer(Scorer), as these may be synthetic Scorers produced by BulkScorer which will throw an Exception.

Throws:

IOException

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

iterator

public abstract DocIdSetIterator iterator()

Return a DocIdSetIterator over matching documents. The returned iterator will either be positioned on -1 if no documents have been scored yet, DocIdSetIterator.NO_MORE_DOCS if all documents have been scored already, or the last document id that has been scored otherwise. The returned iterator is a view: calling this method several times will return iterators that have the same state.

twoPhaseIterator

public TwoPhaseIterator twoPhaseIterator()

Optional method: Return a TwoPhaseIterator view of this Scorer. A return value of null indicates that two-phase iteration is not supported. Note that the returned TwoPhaseIterator's approximation must advance synchronously with the iterator(): advancing the approximation must advance the iterator and vice-versa. Implementing this method is typically useful on Scorers that have a high per-document overhead in order to confirm matches. The default implementation returns null.