org.apache.lucene.search

Class ConstantScoreScorer

java.lang.Object

org.apache.lucene.search.DocIdSetIterator

org.apache.lucene.search.Scorer

org.apache.lucene.search.ConstantScoreScorer

public final class ConstantScoreScorer
extends Scorer

A constant-scoring Scorer.

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.Scorer

Scorer.ChildScorer

Field Summary

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

weight

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

NO_MORE_DOCS

Constructor Summary

Constructors

Constructor and Description
ConstantScoreScorer(Weight weight, float score, DocIdSetIterator disi) Constructor based on a DocIdSetIterator which will be used to drive iteration.
ConstantScoreScorer(Weight weight, float score, TwoPhaseIterator twoPhaseIterator) Constructor based on a TwoPhaseIterator.

Method Summary

Methods

Modifier and Type	Method and Description
int	advance(int target) Advances to the first beyond the current whose document number is greater than or equal to target, and returns the document number itself.
TwoPhaseIterator	asTwoPhaseIterator() Optional method: Return a TwoPhaseIterator view of this Scorer.
long	cost() Returns the estimated cost of this DocIdSetIterator.
int	docID() Returns the following: -1 if DocIdSetIterator.nextDoc() or DocIdSetIterator.advance(int) were not called yet.
int	freq() Returns the freq of this Scorer on the current document
int	nextDoc() Advances to the next document in the set and returns the doc it is currently on, or DocIdSetIterator.NO_MORE_DOCS if there are no more docs in the set. NOTE: after the iterator has exhausted you should not call this method, as it may result in unpredicted behavior.
float	score() Returns the score of the current document matching the query.

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

getChildren, getWeight

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

all, empty, slowAdvance

Methods inherited from class java.lang.Object

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

Constructor Detail

ConstantScoreScorer

public ConstantScoreScorer(Weight weight,
                   float score,
                   DocIdSetIterator disi)

Constructor based on a DocIdSetIterator which will be used to drive iteration. Two phase iteration will not be supported.

Parameters:

weight - the parent weight

score - the score to return on each document

disi - the iterator that defines matching documents

ConstantScoreScorer

public ConstantScoreScorer(Weight weight,
                   float score,
                   TwoPhaseIterator twoPhaseIterator)

Constructor based on a TwoPhaseIterator. In that case the Scorer will support two-phase iteration.

Parameters:

weight - the parent weight

score - the score to return on each document

twoPhaseIterator - the iterator that defines matching documents

Method Detail

asTwoPhaseIterator

public TwoPhaseIterator asTwoPhaseIterator()

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 this iterator: advancing the approximation must advance this 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:

asTwoPhaseIterator in class Scorer

score

public float score()
            throws IOException

Description copied from class: Scorer

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 LeafCollector.collect(int).

Specified by:

score in class Scorer

Throws:

IOException

freq

public int freq()
         throws IOException

Description copied from class: Scorer

Returns the freq of this Scorer on the current document

Specified by:

freq in class Scorer

Throws:

IOException

docID

public int docID()

Description copied from class: DocIdSetIterator

Returns the following:

• -1 if DocIdSetIterator.nextDoc() or DocIdSetIterator.advance(int) were not called yet.
• DocIdSetIterator.NO_MORE_DOCS if the iterator has exhausted.
• Otherwise it should return the doc ID it is currently on.

Specified by:

docID in class DocIdSetIterator

nextDoc

public int nextDoc()
            throws IOException

Description copied from class: DocIdSetIterator

Advances to the next document in the set and returns the doc it is currently on, or DocIdSetIterator.NO_MORE_DOCS if there are no more docs in the set.
NOTE: after the iterator has exhausted you should not call this method, as it may result in unpredicted behavior.

Specified by:

nextDoc in class DocIdSetIterator

Throws:

IOException

advance

public int advance(int target)
            throws IOException

Description copied from class: DocIdSetIterator

Advances to the first beyond the current whose document number is greater than or equal to target, and returns the document number itself. Exhausts the iterator and returns DocIdSetIterator.NO_MORE_DOCS if target is greater than the highest document number in the set.

The behavior of this method is undefined when called with target ≤ current, or after the iterator has exhausted. Both cases may result in unpredicted behavior.

When target > current it behaves as if written:

 int advance(int target) {
   int doc;
   while ((doc = nextDoc()) < target) {
   }
   return doc;
 }
 

Some implementations are considerably more efficient than that.

NOTE: this method may be called with DocIdSetIterator.NO_MORE_DOCS for efficiency by some Scorers. If your implementation cannot efficiently determine that it should exhaust, it is recommended that you check for that value in each call to this method.

Specified by:

advance in class DocIdSetIterator

Throws:

IOException

cost

public long cost()

Description copied from class: DocIdSetIterator

Returns the estimated cost of this DocIdSetIterator.

This is generally an upper bound of the number of documents this iterator might match, but may be a rough heuristic, hardcoded value, or otherwise completely inaccurate.

Specified by:

cost in class DocIdSetIterator