org.apache.lucene.search
Class ScoreCachingWrappingScorer

java.lang.Object
  extended by org.apache.lucene.search.DocIdSetIterator
      extended by org.apache.lucene.search.Scorer
          extended by org.apache.lucene.search.ScoreCachingWrappingScorer

public class ScoreCachingWrappingScorer
extends Scorer

A Scorer which wraps another scorer and caches the score of the current document. Successive calls to score() will return the same result and will not invoke the wrapped Scorer's score() method, unless the current document has changed.
This class might be useful due to the changes done to the Collector interface, in which the score is not computed for a document by default, only if the collector requests it. Some collectors may need to use the score in several places, however all they have in hand is a Scorer object, and might end up computing the score of a document more than once.


Field Summary
 
Fields inherited from class org.apache.lucene.search.DocIdSetIterator
NO_MORE_DOCS
 
Constructor Summary
ScoreCachingWrappingScorer(Scorer scorer)
          Creates a new instance by wrapping the given scorer.
 
Method Summary
 int advance(int target)
          Advances to the first beyond the current whose document number is greater than or equal to target.
 int doc()
          Deprecated. use docID() instead.
 int docID()
          Returns the following: -1 or DocIdSetIterator.NO_MORE_DOCS if DocIdSetIterator.nextDoc() or DocIdSetIterator.advance(int) were not called yet.
 Explanation explain(int doc)
          Returns an explanation of the score for a document.
 Similarity getSimilarity()
          Returns the Similarity implementation used by this scorer.
 boolean next()
          Deprecated. use nextDoc() instead.
 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: in 3.0 this method will become abstract, following the removal of DocIdSetIterator.next().
 float score()
          Returns the score of the current document matching the query.
 void score(Collector collector)
          Scores and collects all matching documents.
protected  boolean score(Collector collector, int max, int firstDocID)
          Expert: Collects matching documents in a range.
 boolean skipTo(int target)
          Deprecated. use advance(int) instead.
 
Methods inherited from class org.apache.lucene.search.Scorer
score, score
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

ScoreCachingWrappingScorer

public ScoreCachingWrappingScorer(Scorer scorer)
Creates a new instance by wrapping the given scorer.

Method Detail

score

protected boolean score(Collector collector,
                        int max,
                        int firstDocID)
                 throws IOException
Description copied from class: Scorer
Expert: Collects matching documents in a range. Hook for optimization. Note, firstDocID is added to ensure that DocIdSetIterator.nextDoc() was called before this method.

Overrides:
score in class Scorer
Parameters:
collector - The collector to which all matching documents are passed.
max - Do not score documents past this.
firstDocID - The first document ID (ensures DocIdSetIterator.nextDoc() is called before this method.
Returns:
true if more matching documents may remain.
Throws:
IOException

getSimilarity

public Similarity getSimilarity()
Description copied from class: Scorer
Returns the Similarity implementation used by this scorer.

Overrides:
getSimilarity in class Scorer

explain

public Explanation explain(int doc)
                    throws IOException
Description copied from class: Scorer
Returns an explanation of the score for a document.
When this method is used, the DocIdSetIterator.next(), DocIdSetIterator.skipTo(int) and Scorer.score(HitCollector) methods should not be used.

Overrides:
explain in class Scorer
Parameters:
doc - The document number for the explanation.
Throws:
IOException

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.next() or DocIdSetIterator.skipTo(int) is called the first time, or when called from within Collector.collect(int).

Specified by:
score in class Scorer
Throws:
IOException

doc

public int doc()
Deprecated. use docID() instead.

Description copied from class: DocIdSetIterator
Unsupported anymore. Call DocIdSetIterator.docID() instead. This method throws UnsupportedOperationException if called.

Overrides:
doc in class DocIdSetIterator

docID

public int docID()
Description copied from class: DocIdSetIterator
Returns the following:

NOTE: in 3.0, this method will become abstract.

Overrides:
docID in class DocIdSetIterator

next

public boolean next()
             throws IOException
Deprecated. use nextDoc() instead.

Description copied from class: DocIdSetIterator
Unsupported anymore. Call DocIdSetIterator.nextDoc() instead. This method throws UnsupportedOperationException if called.

Overrides:
next in class DocIdSetIterator
Throws:
IOException

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: in 3.0 this method will become abstract, following the removal of DocIdSetIterator.next(). For backward compatibility it is implemented as:
 public int nextDoc() throws IOException {
   return next() ? doc() : NO_MORE_DOCS;
 }
 
NOTE: after the iterator has exhausted you should not call this method, as it may result in unpredicted behavior.

Overrides:
nextDoc in class DocIdSetIterator
Throws:
IOException

score

public void score(Collector collector)
           throws IOException
Description copied from class: Scorer
Scores and collects all matching documents.

Overrides:
score in class Scorer
Parameters:
collector - The collector to which all matching documents are passed.
When this method is used the Scorer.explain(int) method should not be used.
Throws:
IOException

skipTo

public boolean skipTo(int target)
               throws IOException
Deprecated. use advance(int) instead.

Description copied from class: DocIdSetIterator
Unsupported anymore. Call DocIdSetIterator.advance(int) instead. This method throws UnsupportedOperationException if called.

Overrides:
skipTo 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. Returns the current document number or DocIdSetIterator.NO_MORE_DOCS if there are no more docs in the set.

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: certain implementations may return a different value (each time) if called several times in a row with the same target.

NOTE: this method may be called with 2147483647 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.

NOTE: after the iterator has exhausted you should not call this method, as it may result in unpredicted behavior.

NOTE: in 3.0 this method will become abstract, following the removal of DocIdSetIterator.skipTo(int).

Overrides:
advance in class DocIdSetIterator
Throws:
IOException


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