io.lettuce.core.search.arguments

Enum ScoringFunction

java.lang.Object

java.lang.Enum<ScoringFunction>

io.lettuce.core.search.arguments.ScoringFunction

All Implemented Interfaces:

Serializable, Comparable<ScoringFunction>

public enum ScoringFunction
extends Enum<ScoringFunction>

Scoring function for search queries.

The scoring function determines how the relevance of a document is calculated.

The default scoring function is TF_IDF.

Since:

6.8

Author:

Tihomir Mateev

See Also:

Scoring

Enum Constant Summary

Enum Constants

Enum Constant and Description
BM25 A variation on the basic TFIDF scorer.
DIS_MAX A simple scorer that sums up the frequencies of matched terms.
DOCUMENT_SCORE A scoring function that just returns the presumptive score of the document without applying any calculations to it.
HAMMING_DISTANCE Scoring by the inverse Hamming distance between the document's payload and the query payload is performed.
TF_IDF Term Frequency - Inverse Document Frequency.
TF_IDF_NORMALIZED Term Frequency - Inverse Document Frequency with document normalization.

Method Summary

Modifier and Type	Method and Description
String	toString()
static ScoringFunction	valueOf(String name) Returns the enum constant of this type with the specified name.
static ScoringFunction[]	values() Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum

clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Detail

TF_IDF

public static final ScoringFunction TF_IDF

Term Frequency - Inverse Document Frequency.

This is the default setting.

See Also:

Wikipedia

TF_IDF_NORMALIZED

public static final ScoringFunction TF_IDF_NORMALIZED

Term Frequency - Inverse Document Frequency with document normalization.

Identical to the default TFIDF scorer, with one important distinction - term frequencies are normalized by the length of the document, expressed as the total number of terms. The length is weighted, so that if a document contains two terms, one in a field that has a weight 1 and one in a field with a weight of 5, the total frequency is 6, not 2.

See Also:

Wikipedia

BM25

public static final ScoringFunction BM25

A variation on the basic TFIDF scorer. The relevance score for each document is multiplied by the presumptive document score, and a penalty is applied based on slop as in TFIDF.

See Also:

Wikipedia

DIS_MAX

public static final ScoringFunction DIS_MAX

A simple scorer that sums up the frequencies of matched terms. In the case of union clauses, it will give the maximum value of those matches. No other penalties or factors are applied.

See Also:

DisMax

DOCUMENT_SCORE

public static final ScoringFunction DOCUMENT_SCORE

A scoring function that just returns the presumptive score of the document without applying any calculations to it. Since document scores can be updated, this can be useful if you'd like to use an external score and nothing further.

HAMMING_DISTANCE

public static final ScoringFunction HAMMING_DISTANCE

Scoring by the inverse Hamming distance between the document's payload and the query payload is performed. Since the nearest neighbors are of interest, the inverse Hamming distance (1/(1+d)) is used so that a distance of 0 gives a perfect score of 1 and is the highest rank.

This only works if:

• The document has a payload.
• The query has a payload.
• Both are exactly the same length.

Payloads are binary-safe, and having payloads with a length that is a multiple of 64 bits yields slightly faster results.

See Also:

Wikipedia

Method Detail

values

public static ScoringFunction[] values()

Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

for (ScoringFunction c : ScoringFunction.values())
    System.out.println(c);

Returns:

an array containing the constants of this enum type, in the order they are declared

valueOf

public static ScoringFunction valueOf(String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

IllegalArgumentException - if this enum type has no constant with the specified name

NullPointerException - if the argument is null

toString

public String toString()

Overrides:

toString in class Enum<ScoringFunction>