Class Weight

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.

IndexSearcher dependent state of the query should reside in the Weight.

AtomicReader dependent state should reside in the Scorer.

Since Weight creates Scorer instances for a given AtomicReaderContext (GetScorer(AtomicReaderContext, IBits)) callers must maintain the relationship between the searcher's top-level IndexReaderContext and the context used to create a Scorer.

A Weight is used in the following way:

  1. A Weight is constructed by a top-level query, given a IndexSearcher (CreateWeight(IndexSearcher)).
  2. The GetValueForNormalization() method is called on the Weight to compute the query normalization factor QueryNorm(Single) of the query clauses contained in the query.
  3. The query normalization factor is passed to Normalize(Single, Single). At this point the weighting is complete.
  4. A Scorer is constructed by GetScorer(AtomicReaderContext, IBits).

@since 2.9

Inheritance
System.Object
Weight
FunctionQuery.FunctionWeight
BooleanQuery.BooleanWeight
ConstantScoreQuery.ConstantWeight
DisjunctionMaxQuery.DisjunctionMaxWeight
SpanWeight
Assembly: DistributedLucene.Net.dll
Syntax
public abstract class Weight : object

Properties

Name Description
Query

The query that this concerns.

ScoresDocsOutOfOrder

Returns true if this implementation scores docs only out of order. This method is used in conjunction with ICollector's AcceptsDocsOutOfOrder and GetBulkScorer(AtomicReaderContext, Boolean, IBits) to create a matching Scorer instance for a given ICollector, or vice versa.

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

Methods

Name Description
Explain(AtomicReaderContext, Int32)

An explanation of the score computation for the named document.
GetBulkScorer(AtomicReaderContext, Boolean, IBits)

Optional method, to return a BulkScorer to score the query and send hits to a ICollector. Only queries that have a different top-level approach need to override this; the default implementation pulls a normal Scorer and iterates and collects the resulting hits.
GetScorer(AtomicReaderContext, IBits)

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.
GetValueForNormalization()

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

Normalize(Single, Single)

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

Extension Methods