org.apache.lucene.search

Class Scorer

java.lang.Object

org.apache.lucene.search.DocIdSetIterator

org.apache.lucene.search.Scorer

Direct Known Subclasses:

ConstantScoreScorer, FilterScorer, 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.ChildScorer A child Scorer and its relationship to its parent.

Field Summary

Fields

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

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

NO_MORE_DOCS

Constructor Summary

Constructors

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

Method Summary

Methods

Modifier and Type	Method and Description
TwoPhaseIterator	asTwoPhaseIterator() Optional method: Return a TwoPhaseIterator view of this Scorer.
abstract int	freq() Returns the freq of this Scorer on the current document
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.

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

advance, all, 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 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 LeafCollector.collect(int).

Throws:

IOException

freq

public abstract int freq()
                  throws IOException

Returns the freq of this Scorer on the current document

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()

Returns child sub-scorers

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

asTwoPhaseIterator

public TwoPhaseIterator asTwoPhaseIterator()

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 this iterator: advancing the approximation must advance this 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.