Class PerFieldSimilarityWrapper

Provides the ability to use a different Similarity for different fields.

Subclasses should implement Get(string) to return an appropriate Similarity (for example, using field-specific parameter values) for the field.

Note

This API is experimental and might change in incompatible ways in the next release.

Inheritance

object

Similarity

PerFieldSimilarityWrapper

Inherited Members

Similarity.Coord(int, int)

Similarity.QueryNorm(float)

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

object.ToString()

Namespace: Lucene.Net.Search.Similarities

Assembly: Lucene.Net.dll

Syntax

public abstract class PerFieldSimilarityWrapper : Similarity

Constructors

PerFieldSimilarityWrapper()

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

Declaration

protected PerFieldSimilarityWrapper()

Methods

ComputeNorm(FieldInvertState)

Computes the normalization value for a field, given the accumulated state of term processing for this field (see FieldInvertState).

Matches in longer fields are less precise, so implementations of this method usually set smaller values when state.Length is large, and larger values when

state.Length

is small.

Note

This API is experimental and might change in incompatible ways in the next release.

Declaration

public override sealed long ComputeNorm(FieldInvertState state)

Parameters

Type	Name	Description
FieldInvertState	state	current processing state for this field

Returns

Type	Description
long	computed norm value

Overrides

Similarity.ComputeNorm(FieldInvertState)

ComputeWeight(float, CollectionStatistics, params TermStatistics[])

Compute any collection-level weight (e.g. IDF, average document length, etc) needed for scoring a query.

Declaration

public override sealed Similarity.SimWeight ComputeWeight(float queryBoost, CollectionStatistics collectionStats, params TermStatistics[] termStats)

Parameters

Type	Name	Description
float	queryBoost	the query-time boost.
CollectionStatistics	collectionStats	collection-level statistics, such as the number of tokens in the collection.
TermStatistics[]	termStats	term-level statistics, such as the document frequency of a term across the collection.

Returns

Type	Description
Similarity.SimWeight	Similarity.SimWeight object with the information this Similarity needs to score a query.

Overrides

Similarity.ComputeWeight(float, CollectionStatistics, params TermStatistics[])

Get(string)

Returns a Similarity for scoring a field.

Declaration

public abstract Similarity Get(string name)

Parameters

Type	Name	Description
string	name

Returns

Type	Description
Similarity

GetSimScorer(SimWeight, AtomicReaderContext)

Creates a new Similarity.SimScorer to score matching documents from a segment of the inverted index.

Declaration

public override sealed Similarity.SimScorer GetSimScorer(Similarity.SimWeight weight, AtomicReaderContext context)

Parameters

Type	Name	Description
Similarity.SimWeight	weight	collection information from ComputeWeight(float, CollectionStatistics, params TermStatistics[])
AtomicReaderContext	context	segment of the inverted index to be scored.

Returns

Type	Description
Similarity.SimScorer	Sloppy Similarity.SimScorer for scoring documents across context

Overrides

Similarity.GetSimScorer(Similarity.SimWeight, AtomicReaderContext)

Exceptions

Type	Condition
IOException	if there is a low-level I/O error