org.apache.lucene.search

Class Scorer

java.lang.Object

org.apache.lucene.search.Scorable

org.apache.lucene.search.Scorer

Direct Known Subclasses:

ConstantScoreScorer, FilterScorer, IndriScorer, SpanScorer

public abstract class Scorer
extends Scorable

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/interfaces inherited from class org.apache.lucene.search.Scorable

Scorable.ChildScorable

Field Summary

Fields

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

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method and Description
int	advanceShallow(int target) Advance to the block of documents that contains target in order to get scoring information about this block.
abstract float	getMaxScore(int upTo) Return the maximum score that documents between the last target that this iterator was shallow-advanced to included and upTo included.
Weight	getWeight() returns parent Weight
abstract DocIdSetIterator	iterator() Return a DocIdSetIterator over matching documents.
TwoPhaseIterator	twoPhaseIterator() Optional method: Return a TwoPhaseIterator view of this Scorer.

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

docID, getChildren, score, setMinCompetitiveScore, smoothingScore

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

Constructor Detail

Scorer

protected Scorer(Weight weight)

Constructs a Scorer

Parameters:

weight - The scorers Weight.

Method Detail

getWeight

public Weight getWeight()

returns parent Weight

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.

advanceShallow

public int advanceShallow(int target)
                   throws IOException

Advance to the block of documents that contains target in order to get scoring information about this block. This method is implicitly called by DocIdSetIterator.advance(int) and DocIdSetIterator.nextDoc() on the returned doc ID. Calling this method doesn't modify the current DocIdSetIterator.docID(). It returns a number that is greater than or equal to all documents contained in the current block, but less than any doc IDS of the next block. target must be >= Scorable.docID() as well as all targets that have been passed to advanceShallow(int) so far.

Throws:

IOException

getMaxScore

public abstract float getMaxScore(int upTo)
                           throws IOException

Return the maximum score that documents between the last target that this iterator was shallow-advanced to included and upTo included.

Throws:

IOException