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From "Kyle Maxwell (JIRA)" <>
Subject [jira] Updated: (LUCENE-1019) CustomScoreQuery should support multiple ValueSourceQueries
Date Fri, 05 Oct 2007 22:34:50 GMT


Kyle Maxwell updated LUCENE-1019:

    Attachment: CustomScoreQuery.v1.diff

Here's a slightly simpler version of the diff (v1).

The default behavior of CustomScoreQuery with multiple ValueSourceQueries does not matter
to me.  I really want to be able to override it with custom logic.  Also note that multiplying
twice is currently as simple as CustomScoreQuery(CustomScoreQuery(subQuery, value1), value2).
 But what about things that aren't linear combinations?

Use case:  I want the score to fall off exponentially as content ages, with a decay rate that
varies on a per document basis.  

Each document has three fields: "text," "created-at," and "half-life."  Created-at is represented
as a UNIX timestamp, and half-life in seconds.  I'm not sure that the following query is able
to be expressed as nested queries.  There may be another way to do this, but this seems simple
and elegant to me.

public class DateDecayQuery extends CustomScoreQuery {
	public final double LOG2 = Math.log(2);
	private long now;

	public DateDecayQuery(Query subQuery) {
		super(subQuery, new ValueSourceQuery[] {
				new FieldScoreQuery("date", Type.INT),
				new FieldScoreQuery("half-life", Type.INT) });
		now = new Date().getTime() / 1000; // UNIX timestamp;

	public float customScore(int doc, float score, float fields[]) {
		float date = fields[0];
		float halfLife = fields[1];
		float dateScore = (float) Math.exp(LOG2 * (date - now) / halfLife);
		return score * dateScore;

> CustomScoreQuery should support multiple ValueSourceQueries
> -----------------------------------------------------------
>                 Key: LUCENE-1019
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Search
>    Affects Versions: 2.2
>            Reporter: Kyle Maxwell
>         Attachments: CustomMultiQuery.v0.diff, CustomScoreQuery.v1.diff
> CustomScoreQuery's constructor currently accepts a subQuery, and a ValueSourceQuery.
 I would like it to accept multiple ValueSourceQueries.  The workaround of nested CustomScoreQueries
works for simple cases, but it quickly becomes either cumbersome to manage, or impossible
to implement the desired function.
> This patch implements CustomMultiScoreQuery with my desired functionality, and refactors
CustomScoreQuery to implement the special case of a CustomMultiScoreQuery with 0 or 1 ValueSourceQueries.
 This keeps the CustomScoreQuery API intact.
> This patch includes basic tests, more or less taken from the original implementation,
and customized a bit to cover the new cases.

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