Package org.apache.lucene.search

Class TermScorer

java.lang.Object

org.apache.lucene.search.Scorable

org.apache.lucene.search.Scorer

org.apache.lucene.search.TermScorer

public final class TermScorer
extends Scorer

Expert: A Scorer for documents matching a Term.

NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

Nested Class Summary

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

Scorable.ChildScorable

Field Summary

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

weight

Constructor Summary

Constructors

Constructor	Description
TermScorer(Weight weight, ImpactsEnum impactsEnum, LeafSimScorer docScorer, boolean topLevelScoringClause)	Construct a TermScorer that will use impacts to skip blocks of non-competitive documents.
TermScorer(Weight weight, PostingsEnum postingsEnum, LeafSimScorer docScorer)	Construct a TermScorer that will iterate all documents.

Method Summary

Modifier and Type	Method	Description
int	advanceShallow(int target)	Advance to the block of documents that contains target in order to get scoring information about this block.
int	docID()	Returns the doc ID that is currently being scored.
int	freq()	Returns term frequency in the current document.
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.
float	score()	Returns the score of the current document matching the query.
void	setMinCompetitiveScore(float minScore)	Optional method: Tell the scorer that its iterator may safely ignore all documents whose score is less than the given minScore.
float	smoothingScore(int docId)	Returns the smoothing score of the current document matching the query.
String	toString()	Returns a string representation of this TermScorer.

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

getWeight, twoPhaseIterator

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

getChildren

Methods inherited from class java.lang.Object

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

Constructor Detail

TermScorer

public TermScorer(Weight weight,
                  PostingsEnum postingsEnum,
                  LeafSimScorer docScorer)

Construct a TermScorer that will iterate all documents.

TermScorer

public TermScorer(Weight weight,
                  ImpactsEnum impactsEnum,
                  LeafSimScorer docScorer,
                  boolean topLevelScoringClause)

Construct a TermScorer that will use impacts to skip blocks of non-competitive documents.

Method Detail

docID

public int docID()

Description copied from class: Scorable

Returns the doc ID that is currently being scored.

Specified by:

docID in class Scorable

freq

public final int freq()
               throws IOException

Returns term frequency in the current document.

Throws:

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

score

public float score()
            throws IOException

Description copied from class: Scorable

Returns the score of the current document matching the query.

Specified by:

score in class Scorable

Throws:

IOException

smoothingScore

public float smoothingScore(int docId)
                     throws IOException

Description copied from class: Scorable

Returns the smoothing score of the current document matching the query. This score is used when the query/term does not appear in the document, and behaves like an idf. The smoothing score is particularly important when the Scorer returns a product of probabilities so that the document score does not go to zero when one probability is zero. This can return 0 or a smoothing score.

Smoothing scores are described in many papers, including: Metzler, D. and Croft, W. B. , "Combining the Language Model and Inference Network Approaches to Retrieval," Information Processing and Management Special Issue on Bayesian Networks and Information Retrieval, 40(5), pp.735-750.

Overrides:

smoothingScore in class Scorable

Throws:

IOException

advanceShallow

public int advanceShallow(int target)
                   throws IOException

Description copied from class: Scorer

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 Scorer.advanceShallow(int) so far.

Overrides:

advanceShallow in class Scorer

Throws:

IOException

getMaxScore

public float getMaxScore(int upTo)
                  throws 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:

IOException

setMinCompetitiveScore

public void setMinCompetitiveScore(float minScore)

Description copied from class: Scorable

Optional method: Tell the scorer that its iterator may safely ignore all documents whose score is less than the given minScore. This is a no-op by default.

This method may only be called from collectors that use ScoreMode.TOP_SCORES, and successive calls may only set increasing values of minScore.

Overrides:

setMinCompetitiveScore in class Scorable

toString

public String toString()

Returns a string representation of this TermScorer.

Overrides:

toString in class Object