Package org.apache.lucene.queries.function

Class ValueSourceScorer

java.lang.Object

org.apache.lucene.search.Scorable

org.apache.lucene.search.Scorer

org.apache.lucene.queries.function.ValueSourceScorer

public abstract class ValueSourceScorer
extends Scorer

Scorer which returns the result of FunctionValues.floatVal(int) as the score for a document, and which filters out documents that don't match matches(int). This Scorer has a TwoPhaseIterator. This is similar to FunctionQuery, with an added filter.

Note: If the scores are needed, then the underlying value will probably be fetched/computed twice -- once to filter and next to return the score. If that's non-trivial then consider wrapping it in an implementation that will cache the current value.

See Also:

FunctionQuery

Nested Class Summary

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

Scorable.ChildScorable

Field Summary

Fields

Modifier and Type	Field	Description
private static int	DEF_COST
private DocIdSetIterator	disi
private TwoPhaseIterator	twoPhaseIterator
protected FunctionValues	values

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

weight

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	ValueSourceScorer(Weight weight, LeafReaderContext readerContext, FunctionValues values)

Method Summary

Modifier and Type	Method	Description
int	docID()	Returns the doc ID that is currently being scored.
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.
DocIdSetIterator	iterator()	Return a DocIdSetIterator over matching documents.
protected float	matchCost()	Cost evaluation function which defines the cost of access for the TwoPhaseIterator for this class This method should be overridden for specifying custom cost methods.
abstract boolean	matches(int doc)	Override to decide if this document matches.
float	score()	Returns the score of the current document matching the query.
TwoPhaseIterator	twoPhaseIterator()	Optional method: Return a TwoPhaseIterator view of this Scorer.

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

advanceShallow, getWeight

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

getChildren, setMinCompetitiveScore, smoothingScore

Methods inherited from class java.lang.Object

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

Field Detail

DEF_COST

private static final int DEF_COST

See Also:

Constant Field Values

values

protected final FunctionValues values

twoPhaseIterator

private final TwoPhaseIterator twoPhaseIterator

disi

private final DocIdSetIterator disi

Constructor Detail

ValueSourceScorer

protected ValueSourceScorer(Weight weight,
                            LeafReaderContext readerContext,
                            FunctionValues values)

Method Detail

matches

public abstract boolean matches(int doc)
                         throws java.io.IOException

Override to decide if this document matches. It's called by TwoPhaseIterator.matches().

Throws:

java.io.IOException

iterator

public DocIdSetIterator iterator()

Description copied from class: Scorer

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.

Specified by:

iterator in class Scorer

twoPhaseIterator

public TwoPhaseIterator twoPhaseIterator()

Description copied from class: Scorer

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 Scorer.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.

Overrides:

twoPhaseIterator in class Scorer

docID

public int docID()

Description copied from class: Scorable

Returns the doc ID that is currently being scored.

Specified by:

docID in class Scorable

score

public float score()
            throws java.io.IOException

Description copied from class: Scorable

Returns the score of the current document matching the query.

Specified by:

score in class Scorable

Throws:

java.io.IOException

getMaxScore

public float getMaxScore(int upTo)
                  throws java.io.IOException

Description copied from class: Scorer

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

Specified by:

getMaxScore in class Scorer

Throws:

java.io.IOException

matchCost

protected float matchCost()

Cost evaluation function which defines the cost of access for the TwoPhaseIterator for this class This method should be overridden for specifying custom cost methods. Used by TwoPhaseIterator.matchCost() for the instance owned by this class

Returns:

cost of access