org.apache.lucene.search

Interface Weight

All Superinterfaces:

java.io.Serializable

All Known Implementing Classes:

SpanWeight

public interface Weight
extends java.io.Serializable

Expert: Calculate query weights and build query scorers.

The purpose of Weight is to make it so that 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 (Query.createWeight(Searcher)).
2. The sumOfSquaredWeights() method is called on the Weight to compute the query normalization factor Similarity.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).

Method Summary

Modifier and Type	Method and Description
Explanation	explain(IndexReader reader, int doc) An explanation of the score computation for the named document.
Query	getQuery() The query that this concerns.
float	getValue() The weight for this query.
void	normalize(float norm) Assigns the query normalization factor to this.
Scorer	scorer(IndexReader reader) Constructs a scorer for this.
float	sumOfSquaredWeights() The sum of squared weights of contained query clauses.

Method Detail

getQuery

Query getQuery()

The query that this concerns.

getValue

float getValue()

The weight for this query.

sumOfSquaredWeights

float sumOfSquaredWeights()
                   throws java.io.IOException

The sum of squared weights of contained query clauses.

Throws:

java.io.IOException

normalize

void normalize(float norm)

Assigns the query normalization factor to this.

scorer

Scorer scorer(IndexReader reader)
       throws java.io.IOException

Constructs a scorer for this.

Throws:

java.io.IOException

explain

Explanation explain(IndexReader reader,
                    int doc)
             throws java.io.IOException

An explanation of the score computation for the named document.

Throws:

java.io.IOException