org.apache.lucene.search

Class Scorer

java.lang.Object

org.apache.lucene.search.DocIdSetIterator

org.apache.lucene.search.Scorer

Direct Known Subclasses:

ConstantScoreQuery.ConstantScorer, ReqExclScorer, ReqOptSumScorer, SpanScorer

public abstract class Scorer
extends DocIdSetIterator

Expert: Common scoring functionality for different types of queries.

A Scorer either iterates over documents matching a query in increasing order of doc Id, or provides an explanation of the score for a query for a given document.

Document scores are computed using a given Similarity implementation.

See Also:

BooleanQuery.setAllowDocsOutOfOrder(boolean)

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	Scorer(Similarity similarity) Constructs a Scorer.

Method Summary

Methods

Modifier and Type	Method and Description
abstract Explanation	explain(int doc) Returns an explanation of the score for a document.
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(HitCollector hc) Scores and collects all matching documents.
protected boolean	score(HitCollector hc, int max) Expert: Collects matching documents in a range.

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

doc, next, skipTo

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(HitCollector hc)
           throws IOException

Scores and collects all matching documents.

Parameters:

hc - The collector to which all matching documents are passed through HitCollector.collect(int, float).
When this method is used the explain(int) method should not be used.

Throws:

IOException

score

protected boolean score(HitCollector hc,
            int max)
                 throws IOException

Expert: Collects matching documents in a range. Hook for optimization. Note that DocIdSetIterator.next() must be called once before this method is called for the first time.

Parameters:

hc - The collector to which all matching documents are passed through HitCollector.collect(int, float).

max - Do not score documents past this.

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.next() or DocIdSetIterator.skipTo(int) is called the first time.

Throws:

IOException

explain

public abstract Explanation explain(int doc)
                             throws IOException

Returns an explanation of the score for a document.
When this method is used, the DocIdSetIterator.next(), DocIdSetIterator.skipTo(int) and score(HitCollector) methods should not be used.

Parameters:

doc - The document number for the explanation.

Throws:

IOException