public abstract class

Weight

extends Object
implements Serializable
java.lang.Object
   ↳ org.apache.lucene.search.Weight
Known Direct Subclasses
Known Indirect Subclasses

Class Overview

Expert: Calculate query weights and build query scorers.

The purpose of Weight is to ensure searching does not modify a Query, so that a Query instance can be reused.
Searcher dependent state of the query should reside in the Weight.
IndexReader dependent state should reside in the Scorer.

A Weight is used in the following way:

  1. A Weight is constructed by a top-level query, given a Searcher (createWeight(Searcher)).
  2. The sumOfSquaredWeights() method is called on the Weight to compute the query normalization factor queryNorm(float) of the query clauses contained in the query.
  3. The query normalization factor is passed to normalize(float). At this point the weighting is complete.
  4. A Scorer is constructed by scorer(IndexReader, boolean, boolean).

Summary

Public Constructors
Weight()
Public Methods
abstract Explanation explain(IndexReader reader, int doc)
An explanation of the score computation for the named document.
abstract Query getQuery()
The query that this concerns.
abstract float getValue()
The weight for this query.
abstract void normalize(float norm)
Assigns the query normalization factor to this.
abstract Scorer scorer(IndexReader reader, boolean scoreDocsInOrder, boolean topScorer)
Returns a Scorer which scores documents in/out-of order according to scoreDocsInOrder.
boolean scoresDocsOutOfOrder()
Returns true iff this implementation scores docs only out of order.
abstract float sumOfSquaredWeights()
The sum of squared weights of contained query clauses.
[Expand]
Inherited Methods
From class java.lang.Object

Public Constructors

public Weight ()

Public Methods

public abstract Explanation explain (IndexReader reader, int doc)

An explanation of the score computation for the named document.

Parameters
reader sub-reader containing the give doc
Returns
  • an Explanation for the score
Throws
IOException

public abstract Query getQuery ()

The query that this concerns.

public abstract float getValue ()

The weight for this query.

public abstract void normalize (float norm)

Assigns the query normalization factor to this.

public abstract Scorer scorer (IndexReader reader, boolean scoreDocsInOrder, boolean topScorer)

Returns a Scorer which scores documents in/out-of order according to scoreDocsInOrder.

NOTE: even if scoreDocsInOrder is false, it is recommended to check whether the returned Scorer indeed scores documents out of order (i.e., call scoresDocsOutOfOrder()), as some Scorer implementations will always return documents in-order.
NOTE: null can be returned if no documents will be scored by this query.

Parameters
reader the IndexReader for which to return the Scorer.
scoreDocsInOrder specifies whether in-order scoring of documents is required. Note that if set to false (i.e., out-of-order scoring is required), this method can return whatever scoring mode it supports, as every in-order scorer is also an out-of-order one. However, an out-of-order scorer may not support nextDoc() and/or advance(int), therefore it is recommended to request an in-order scorer if use of these methods is required.
topScorer if true, score(Collector) will be called; if false, nextDoc() and/or advance(int) will be called.
Returns
  • a Scorer which scores documents in/out-of order.
Throws
IOException

public boolean scoresDocsOutOfOrder ()

Returns true iff this implementation scores docs only out of order. This method is used in conjunction with Collector's acceptsDocsOutOfOrder and scorer(org.apache.lucene.index.IndexReader, boolean, boolean) to create a matching Scorer instance for a given Collector, or vice versa.

NOTE: the default implementation returns false, i.e. the Scorer scores documents in-order.

public abstract float sumOfSquaredWeights ()

The sum of squared weights of contained query clauses.

Throws
IOException