org.apache.lucene.search.similarities

Class Similarity.SimScorer

java.lang.Object

org.apache.lucene.search.similarities.Similarity.SimScorer

Enclosing class:

Similarity

public abstract static class Similarity.SimScorer
extends Object

Stores the weight for a query across the indexed collection. This abstract implementation is empty; descendants of Similarity should subclass SimWeight and define the statistics they require in the subclass. Examples include idf, average field length, etc.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	SimScorer() Sole constructor.

Method Summary

Modifier and Type	Method and Description
Explanation	explain(Explanation freq, long norm) Explain the score for a single document
abstract float	score(float freq, long norm) Score a single document.

Methods inherited from class java.lang.Object

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

Constructor Detail

SimScorer

protected SimScorer()

Sole constructor. (For invocation by subclass constructors.)

Method Detail

score

public abstract float score(float freq,
                            long norm)

Score a single document. freq is the document-term sloppy frequency and must be finite and positive. norm is the encoded normalization factor as computed by Similarity.computeNorm(FieldInvertState) at index time, or 1 if norms are disabled. norm is never 0.

Score must not decrease when freq increases, ie. if freq1 > freq2, then score(freq1, norm) >= score(freq2, norm) for any value of norm that may be produced by Similarity.computeNorm(FieldInvertState).

Score must not increase when the unsigned norm increases, ie. if Long.compareUnsigned(norm1, norm2) > 0 then score(freq, norm1) <= score(freq, norm2) for any legal freq.

As a consequence, the maximum score that this scorer can produce is bound by score(Float.MAX_VALUE, 1).

Parameters:

freq - sloppy term frequency, must be finite and positive

norm - encoded normalization factor or 1 if norms are disabled

Returns:

document's score

explain

public Explanation explain(Explanation freq,
                           long norm)

Explain the score for a single document

Parameters:

freq - Explanation of how the sloppy term frequency was computed

norm - encoded normalization factor, as returned by Similarity.computeNorm(org.apache.lucene.index.FieldInvertState), or 1 if norms are disabled

Returns:

document's score