org.apache.lucene.search.similarities
Class Similarity.SimWeight

java.lang.Object
  org.apache.lucene.search.similarities.Similarity.SimWeight

Direct Known Subclasses:

BasicStats

Enclosing class:

Similarity

public abstract static class Similarity.SimWeight
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

Similarity.SimWeight()
Sole constructor.

Method Summary

abstract float	getValueForNormalization() The value for normalization of contained query clauses (e.g.
abstract void	normalize(float queryNorm, float topLevelBoost) Assigns the query normalization factor and boost from parent queries to this.

Methods inherited from class java.lang.Object

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

Constructor Detail

Similarity.SimWeight

public Similarity.SimWeight()

Sole constructor. (For invocation by subclass constructors, typically implicit.)

Method Detail

getValueForNormalization

public abstract float getValueForNormalization()

The value for normalization of contained query clauses (e.g. sum of squared weights).

NOTE: a Similarity implementation might not use any query normalization at all, its not required. However, if it wants to participate in query normalization, it can return a value here.

normalize

public abstract void normalize(float queryNorm,
                               float topLevelBoost)

Assigns the query normalization factor and boost from parent queries to this.

NOTE: a Similarity implementation might not use this normalized value at all, its not required. However, its usually a good idea to at least incorporate the topLevelBoost (e.g. from an outer BooleanQuery) into its score.