org.apache.lucene.search.function
Class CustomScoreQuery

java.lang.Object
  org.apache.lucene.search.Query
      org.apache.lucene.search.function.CustomScoreQuery

All Implemented Interfaces:

Serializable, Cloneable

public class CustomScoreQuery
extends Query

Query that sets document score as a programmatic function of several (sub) scores.

1. the score of its subQuery (any query)
2. (optional) the score of its ValueSourceQuery (or queries). For most simple/convenient use cases this query is likely to be a FieldScoreQuery

Subclasses can modify the computation by overriding customScore(int, float, float).

WARNING: The status of the search.function package is experimental. The APIs introduced here might change in the future and will not be supported anymore in such a case.

See Also:

Serialized Form

Constructor Summary

CustomScoreQuery(Query subQuery)
Create a CustomScoreQuery over input subQuery.

CustomScoreQuery(Query subQuery, ValueSourceQuery valSrcQuery)
Create a CustomScoreQuery over input subQuery and a ValueSourceQuery.

CustomScoreQuery(Query subQuery, ValueSourceQuery[] valSrcQueries)
Create a CustomScoreQuery over input subQuery and a ValueSourceQuery.

Method Summary

Object	clone() Returns a clone of this query.
protected Weight	createWeight(Searcher searcher) Expert: Constructs an appropriate Weight implementation for this query.
Explanation	customExplain(int doc, Explanation subQueryExpl, Explanation valSrcExpl) Explain the custom score.
Explanation	customExplain(int doc, Explanation subQueryExpl, Explanation[] valSrcExpls) Explain the custom score.
float	customScore(int doc, float subQueryScore, float valSrcScore) Compute a custom score by the subQuery score and the ValueSourceQuery score.
float	customScore(int doc, float subQueryScore, float[] valSrcScores) Compute a custom score by the subQuery score and a number of ValueSourceQuery scores.
boolean	equals(Object o) Returns true if o is equal to this.
void	extractTerms(Set terms) Expert: adds all terms occuring in this query to the terms set.
int	hashCode() Returns a hash code value for this object.
boolean	isStrict() Checks if this is strict custom scoring.
String	name() A short name of this query, used in toString(String).
Query	rewrite(IndexReader reader) Expert: called to re-write queries into primitive queries.
void	setStrict(boolean strict) Set the strict mode of this query.
String	toString(String field) Prints a query to a string, with field assumed to be the default field and omitted.

Methods inherited from class org.apache.lucene.search.Query

combine, getBoost, getSimilarity, mergeBooleanQueries, setBoost, toString, weight

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

CustomScoreQuery

public CustomScoreQuery(Query subQuery)

Create a CustomScoreQuery over input subQuery.

Parameters:

subQuery - the sub query whose scored is being customed. Must not be null.

CustomScoreQuery

public CustomScoreQuery(Query subQuery,
                        ValueSourceQuery valSrcQuery)

Create a CustomScoreQuery over input subQuery and a ValueSourceQuery.

Parameters:

subQuery - the sub query whose score is being customed. Must not be null.

valSrcQuery - a value source query whose scores are used in the custom score computation. For most simple/convineient use case this would be a FieldScoreQuery. This parameter is optional - it can be null.

CustomScoreQuery

public CustomScoreQuery(Query subQuery,
                        ValueSourceQuery[] valSrcQueries)

Create a CustomScoreQuery over input subQuery and a ValueSourceQuery.

Parameters:

subQuery - the sub query whose score is being customed. Must not be null.

valSrcQueries - value source queries whose scores are used in the custom score computation. For most simple/convineient use case these would be FieldScoreQueries. This parameter is optional - it can be null or even an empty array.

Method Detail

rewrite

public Query rewrite(IndexReader reader)
              throws IOException

Description copied from class: Query

Expert: called to re-write queries into primitive queries. For example, a PrefixQuery will be rewritten into a BooleanQuery that consists of TermQuerys.

Overrides:

rewrite in class Query

Throws:

IOException

extractTerms

public void extractTerms(Set terms)

Description copied from class: Query

Expert: adds all terms occuring in this query to the terms set. Only works if this query is in its rewritten form.

Overrides:

extractTerms in class Query

clone

public Object clone()

Description copied from class: Query

Returns a clone of this query.

Overrides:

clone in class Query

toString

public String toString(String field)

Description copied from class: Query

Prints a query to a string, with field assumed to be the default field and omitted.

The representation used is one that is supposed to be readable by QueryParser. However, there are the following limitations:

• If the query was created by the parser, the printed representation may not be exactly what was parsed. For example, characters that need to be escaped will be represented without the required backslash.
• Some of the more complicated queries (e.g. span queries) don't have a representation that can be parsed by QueryParser.

Specified by:

toString in class Query

equals

public boolean equals(Object o)

Returns true if o is equal to this.

Overrides:

equals in class Object

hashCode

public int hashCode()

Returns a hash code value for this object.

Overrides:

hashCode in class Object

customScore

public float customScore(int doc,
                         float subQueryScore,
                         float[] valSrcScores)

Compute a custom score by the subQuery score and a number of ValueSourceQuery scores.

Subclasses can override this method to modify the custom score.

If your custom scoring is different than the default herein you should override at least one of the two customScore() methods. If the number of ValueSourceQueries is always < 2 it is sufficient to override the other costomScore() method, which is simpler.

The default computation herein is:

     ModifiedScore = valSrcScore * subQueryScore[0] * subQueryScore[1] * ...
 

Parameters:

doc - id of scored doc.

subQueryScore - score of that doc by the subQuery.

valSrcScores - score of that doc by the ValueSourceQuery.

Returns:

custom score.

customScore

public float customScore(int doc,
                         float subQueryScore,
                         float valSrcScore)

Compute a custom score by the subQuery score and the ValueSourceQuery score.

Subclasses can override this method to modify the custom score.

If your custom scoring is different than the default herein you should override at least one of the two customScore() methods. If the number of ValueSourceQueries is always < 2 it is sufficient to override this costomScore() method, which is simpler.

The default computation herein is:

     ModifiedScore = valSrcScore * subQueryScore
 

Parameters:

doc - id of scored doc.

subQueryScore - score of that doc by the subQuery.

valSrcScore - score of that doc by the ValueSourceQuery.

Returns:

custom score.

customExplain

public Explanation customExplain(int doc,
                                 Explanation subQueryExpl,
                                 Explanation[] valSrcExpls)

Explain the custom score. Whenever overriding customScore(int, float, float[]), this method should also be overridden to provide the correct explanation for the part of the custom scoring.

Parameters:

doc - doc being explained.

subQueryExpl - explanation for the sub-query part.

valSrcExpls - explanation for the value source part.

Returns:

an explanation for the custom score

customExplain

public Explanation customExplain(int doc,
                                 Explanation subQueryExpl,
                                 Explanation valSrcExpl)

Explain the custom score. Whenever overriding customScore(int, float, float), this method should also be overridden to provide the correct explanation for the part of the custom scoring.

Parameters:

doc - doc being explained.

subQueryExpl - explanation for the sub-query part.

valSrcExpl - explanation for the value source part.

Returns:

an explanation for the custom score

createWeight

protected Weight createWeight(Searcher searcher)
                       throws IOException

Description copied from class: Query

Expert: Constructs an appropriate Weight implementation for this query.

Only implemented by primitive queries, which re-write to themselves.

Overrides:

createWeight in class Query

Throws:

IOException

isStrict

public boolean isStrict()

Checks if this is strict custom scoring. In strict custom scoring, the ValueSource part does not participate in weight normalization. This may be useful when one wants full control over how scores are modified, and does not care about normalizing by the ValueSource part. One particular case where this is useful if for testing this query.

Note: only has effect when the ValueSource part is not null.

setStrict

public void setStrict(boolean strict)

Set the strict mode of this query.

Parameters:

strict - The strict mode to set.

See Also:

isStrict()

name

public String name()

A short name of this query, used in toString(String).