org.apache.lucene.search

Class DisjunctionSumScorer

java.lang.Object

org.apache.lucene.search.Scorer

org.apache.lucene.search.DisjunctionSumScorer

public class DisjunctionSumScorer
extends Scorer

A Scorer for OR like queries, counterpart of Lucene's ConjunctionScorer. This Scorer implements Scorer.skipTo(int) and uses skipTo() on the given Scorers.

Field Summary

Fields

Modifier and Type	Field and Description
protected int	nrMatchers The number of subscorers that provide the current match.
protected List	subScorers The subscorers.

Constructor Summary

Constructors

Constructor and Description
DisjunctionSumScorer(List subScorers) Construct a DisjunctionScorer, using one as the minimum number of matching subscorers.
DisjunctionSumScorer(List subScorers, int minimumNrMatchers) Construct a DisjunctionScorer.

Method Summary

Methods

Modifier and Type	Method and Description
protected boolean	advanceAfterCurrent() Advance all subscorers after the current document determined by the top of the scorerQueue.
int	doc() Returns the current document number matching the query.
Explanation	explain(int doc) Gives and explanation for the score of a given document.
boolean	next() Advances to the next document matching the query.
int	nrMatchers() Returns the number of subscorers matching the current document.
float	score() Returns the score of the current document matching the query.
boolean	skipTo(int target) Skips to the first match beyond the current whose document number is greater than or equal to a given target.

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

getSimilarity, score, score

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

subScorers

protected final List subScorers

The subscorers.

nrMatchers

protected int nrMatchers

The number of subscorers that provide the current match.

Constructor Detail

DisjunctionSumScorer

public DisjunctionSumScorer(List subScorers,
                    int minimumNrMatchers)

Construct a DisjunctionScorer.

Parameters:

subScorers - A collection of at least two subscorers.

minimumNrMatchers - The positive minimum number of subscorers that should match to match this query.
When minimumNrMatchers is bigger than the number of subScorers, no matches will be produced.
When minimumNrMatchers equals the number of subScorers, it more efficient to use ConjunctionScorer.

DisjunctionSumScorer

public DisjunctionSumScorer(List subScorers)

Construct a DisjunctionScorer, using one as the minimum number of matching subscorers.

Method Detail

next

public boolean next()
             throws IOException

Description copied from class: Scorer

Advances to the next document matching the query.

Specified by:

next in class Scorer

Returns:

true iff there is another document matching the query.
When this method is used the Scorer.explain(int) method should not be used.

Throws:

IOException

advanceAfterCurrent

protected boolean advanceAfterCurrent()
                               throws IOException

Advance all subscorers after the current document determined by the top of the scorerQueue. Repeat until at least the minimum number of subscorers match on the same document and all subscorers are after that document or are exhausted.
On entry the scorerQueue has at least minimumNrMatchers available. At least the scorer with the minimum document number will be advanced.

Returns:

true iff there is a match.
In case there is a match, currentDoc, currentSumScore, and nrMatchers describe the match.

Throws:

IOException

To Do:

Investigate whether it is possible to use skipTo() when the minimum number of matchers is bigger than one, ie. try and use the character of ConjunctionScorer for the minimum number of matchers.

score

public float score()
            throws IOException

Returns the score of the current document matching the query. Initially invalid, until next() is called the first time.

Specified by:

score in class Scorer

Throws:

IOException

doc

public int doc()

Description copied from class: Scorer

Returns the current document number matching the query. Initially invalid, until Scorer.next() is called the first time.

Specified by:

doc in class Scorer

nrMatchers

public int nrMatchers()

Returns the number of subscorers matching the current document. Initially invalid, until next() is called the first time.

skipTo

public boolean skipTo(int target)
               throws IOException

Skips to the first match beyond the current whose document number is greater than or equal to a given target.
When this method is used the explain(int) method should not be used.
The implementation uses the skipTo() method on the subscorers.

Specified by:

skipTo in class Scorer

Parameters:

target - The target document number.

Returns:

true iff there is such a match.

Throws:

IOException

explain

public Explanation explain(int doc)
                    throws IOException

Gives and explanation for the score of a given document.

Specified by:

explain in class Scorer

Parameters:

doc - The document number for the explanation.

Throws:

IOException

To Do:

Show the resulting score. See BooleanScorer.explain() on how to do this.