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.

Field Summary

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

NO_MORE_DOCS

Constructor Summary

protected

Scorer(Similarity similarity) Constructs a Scorer.

Method Summary

Similarity	getSimilarity() Returns the Similarity implementation used by this scorer.
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.

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

Constructor Detail

Scorer

protected Scorer(Similarity similarity)

Constructs a Scorer.

Parameters:

similarity - The Similarity implementation used by this scorer.

Method Detail

getSimilarity

public Similarity getSimilarity()

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.

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