Lucene.Net  3.0.3
Lucene.Net is a port of the Lucene search engine library, written in C# and targeted at .NET runtime users.
 All Classes Namespaces Files Functions Variables Typedefs Enumerations Properties Pages
Public Member Functions | List of all members
Lucene.Net.Search.SimilarityDelegator Class Reference

Expert: Delegating scoring implementation. Useful in Query.GetSimilarity(Searcher) implementations, to override only certain methods of a Searcher's Similiarty implementation.. More...

Inherits Lucene.Net.Search.Similarity.

Inherited by Lucene.Net.Search.BooleanQuery.AnonymousClassSimilarityDelegator, and Lucene.Net.Search.FuzzyLikeThisQuery.FuzzyTermQuery.AnonymousSimilarityDelegator.

Public Member Functions

 SimilarityDelegator (Similarity delegee)
 Construct a Similarity that delegates all methods to another.
 
override float ComputeNorm (System.String fieldName, FieldInvertState state)
 Compute the normalization value for a field, given the accumulated state of term processing for this field (see FieldInvertState).
 
override float LengthNorm (System.String fieldName, int numTerms)
 Computes the normalization value for a field given the total number of terms contained in a field. These values, together with field boosts, are stored in an index and multipled into scores for hits on each field by the search code.
 
override float QueryNorm (float sumOfSquaredWeights)
 Computes the normalization value for a query given the sum of the squared weights of each of the query terms. This value is then multipled into the weight of each query term.
 
override float Tf (float freq)
 Computes a score factor based on a term or phrase's frequency in a document. This value is multiplied by the Idf(int, int) factor for each term in the query and these products are then summed to form the initial score for a document.
 
override float SloppyFreq (int distance)
 Computes the amount of a sloppy phrase match, based on an edit distance. This value is summed for each sloppy phrase match in a document to form the frequency that is passed to Tf(float).
 
override float Idf (int docFreq, int numDocs)
 Computes a score factor based on a term's document frequency (the number of documents which contain the term). This value is multiplied by the Tf(int) factor for each term in the query and these products are then summed to form the initial score for a document.
 
override float Coord (int overlap, int maxOverlap)
 Computes a score factor based on the fraction of all query terms that a document contains. This value is multiplied into scores.
 
override float ScorePayload (int docId, string fieldName, int start, int end, byte[] payload, int offset, int length)
 
- Public Member Functions inherited from Lucene.Net.Search.Similarity
virtual float Tf (int freq)
 Computes a score factor based on a term or phrase's frequency in a document. This value is multiplied by the Idf(int, int) factor for each term in the query and these products are then summed to form the initial score for a document.
 
virtual IDFExplanation IdfExplain (Term term, Searcher searcher)
 Computes a score factor for a simple term and returns an explanation for that score factor.
 
virtual IDFExplanation IdfExplain (ICollection< Term > terms, Searcher searcher)
 Computes a score factor for a phrase.
 
virtual float ScorePayload (int docId, System.String fieldName, int start, int end, byte[] payload, int offset, int length)
 Calculate a scoring factor based on the data in the payload. Overriding implementations are responsible for interpreting what is in the payload. Lucene makes no assumptions about what is in the byte array. The default implementation returns 1.
 

Additional Inherited Members

- Static Public Member Functions inherited from Lucene.Net.Search.Similarity
static float DecodeNorm (byte b)
 Decodes a normalization factor stored in an index.
 
static float[] GetNormDecoder ()
 Returns a table for decoding normalization bytes.
 
static byte EncodeNorm (float f)
 Encodes a normalization factor for storage in an index.
 
- Public Attributes inherited from Lucene.Net.Search.Similarity
const int NO_DOC_ID_PROVIDED = - 1
 
- Protected Member Functions inherited from Lucene.Net.Search.Similarity
 Similarity ()
 
- Properties inherited from Lucene.Net.Search.Similarity
static Similarity Default [get, set]
 Gets or sets the default Similarity implementation used by indexing and search code. This is initially an instance of DefaultSimilarity.
 

Detailed Description

Expert: Delegating scoring implementation. Useful in Query.GetSimilarity(Searcher) implementations, to override only certain methods of a Searcher's Similiarty implementation..

Definition at line 29 of file SimilarityDelegator.cs.

Constructor & Destructor Documentation

Lucene.Net.Search.SimilarityDelegator.SimilarityDelegator ( Similarity  delegee)

Construct a Similarity that delegates all methods to another.

Parameters
delegeethe Similarity implementation to delegate to

Definition at line 35 of file SimilarityDelegator.cs.

Member Function Documentation

override float Lucene.Net.Search.SimilarityDelegator.ComputeNorm ( System.String  field,
FieldInvertState  state 
)
virtual

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

Implementations should calculate a float value based on the field state and then return that value.

For backward compatibility this method by default calls LengthNorm(String, int) passing FieldInvertState.Length as the second argument, and then multiplies this value by FieldInvertState.Boost.

WARNING: This API is new and experimental and may suddenly change.

Parameters
fieldfield name
statecurrent processing state for this field
Returns
the calculated float norm

Reimplemented from Lucene.Net.Search.Similarity.

Definition at line 40 of file SimilarityDelegator.cs.

override float Lucene.Net.Search.SimilarityDelegator.Coord ( int  overlap,
int  maxOverlap 
)
virtual

Computes a score factor based on the fraction of all query terms that a document contains. This value is multiplied into scores.

The presence of a large portion of the query terms indicates a better match with the query, so implementations of this method usually return larger values when the ratio between these parameters is large and smaller values when the ratio between them is small.

Parameters
overlapthe number of query terms matched in the document
maxOverlapthe total number of terms in the query
Returns
a score factor based on term overlap with the query

Implements Lucene.Net.Search.Similarity.

Definition at line 70 of file SimilarityDelegator.cs.

override float Lucene.Net.Search.SimilarityDelegator.Idf ( int  docFreq,
int  numDocs 
)
virtual

Computes a score factor based on a term's document frequency (the number of documents which contain the term). This value is multiplied by the Tf(int) factor for each term in the query and these products are then summed to form the initial score for a document.

Terms that occur in fewer documents are better indicators of topic, so implementations of this method usually return larger values for rare terms, and smaller values for common terms.

Parameters
docFreqthe number of documents which contain the term
numDocsthe total number of documents in the collection
Returns
a score factor based on the term's document frequency

Implements Lucene.Net.Search.Similarity.

Definition at line 65 of file SimilarityDelegator.cs.

override float Lucene.Net.Search.SimilarityDelegator.LengthNorm ( System.String  fieldName,
int  numTokens 
)
virtual

Computes the normalization value for a field given the total number of terms contained in a field. These values, together with field boosts, are stored in an index and multipled into scores for hits on each field by the search code.

Matches in longer fields are less precise, so implementations of this method usually return smaller values when numTokens is large, and larger values when numTokens is small.

Note that the return values are computed under Lucene.Net.Index.IndexWriter.AddDocument(Lucene.Net.Documents.Document) and then stored using EncodeNorm(float). Thus they have limited precision, and documents must be re-indexed if this method is altered.

Parameters
fieldNamethe name of the field
numTokensthe total number of tokens contained in fields named fieldName of doc.
Returns

a normalization factor for hits on this field of this document

See Also
Lucene.Net.Documents.AbstractField.Boost

Implements Lucene.Net.Search.Similarity.

Definition at line 45 of file SimilarityDelegator.cs.

override float Lucene.Net.Search.SimilarityDelegator.QueryNorm ( float  sumOfSquaredWeights)
virtual

Computes the normalization value for a query given the sum of the squared weights of each of the query terms. This value is then multipled into the weight of each query term.

This does not affect ranking, but rather just attempts to make scores from different queries comparable.

Parameters
sumOfSquaredWeightsthe sum of the squares of query term weights
Returns
a normalization factor for query weights

Implements Lucene.Net.Search.Similarity.

Definition at line 50 of file SimilarityDelegator.cs.

override float Lucene.Net.Search.SimilarityDelegator.ScorePayload ( int  docId,
string  fieldName,
int  start,
int  end,
byte[]  payload,
int  offset,
int  length 
)

Definition at line 75 of file SimilarityDelegator.cs.

override float Lucene.Net.Search.SimilarityDelegator.SloppyFreq ( int  distance)
virtual

Computes the amount of a sloppy phrase match, based on an edit distance. This value is summed for each sloppy phrase match in a document to form the frequency that is passed to Tf(float).

A phrase match with a small edit distance to a document passage more closely matches the document, so implementations of this method usually return larger values when the edit distance is small and smaller values when it is large.

See Also
PhraseQuery.Slop
Parameters
distancethe edit distance of this sloppy phrase match
Returns
the frequency increment for this match

Implements Lucene.Net.Search.Similarity.

Definition at line 60 of file SimilarityDelegator.cs.

override float Lucene.Net.Search.SimilarityDelegator.Tf ( float  freq)
virtual

Computes a score factor based on a term or phrase's frequency in a document. This value is multiplied by the Idf(int, int) factor for each term in the query and these products are then summed to form the initial score for a document.

Terms and phrases repeated in a document indicate the topic of the document, so implementations of this method usually return larger values when freq is large, and smaller values when freq is small.

Parameters
freqthe frequency of a term within a document
Returns
a score factor based on a term's within-document frequency

Implements Lucene.Net.Search.Similarity.

Definition at line 55 of file SimilarityDelegator.cs.


The documentation for this class was generated from the following file: