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From Sebastian Marius Kirsch <skir...@sebastian-kirsch.org>
Subject Scoring with FunctionQueries?
Date Tue, 07 Mar 2006 18:15:34 GMT
Hello,

I have been trying out Yonik's excellent FunctionQuery (from Solr),
but am having some problems regarding the scoring of FunctionQueries
in conjunction with other queries.

I am currently researching a data fusion approach, where you have
several separate scores for a document and combine them to produce a
composite score. One of these scores is the regular Lucene score,
which I essentially treat as a black box.

I'm trying a simple linear combination, ie.

score = a * score_a + b * score_b ...

I have one Query produced by a QueryParser, and one (possibly several)
FunctionQueries which provide additional scores. I combine them with a
BooleanQuery with required clauses.

When I look at the explanation of such a combined Query, I see that
the scores of the subqueries are all multiplied by the query norm --
but I want only the score of the full-text query to be multiplied by
the query norm. The function queries should be added to the final
query as they are (the factors a, b, ... could be set using a query
boost.)

How do I achieve that? I'm rather lost in the forest of Scorer,
Similarity and Weight right now. Which is the right place to add such
a modification, so that it doesn't mess up the rest of the scoring?


I already tried extending BooleanQuery so that getSimilarity returns a
Similarity which overloads just queryNorm, to return 1.0. But this
queryNorm is then used both for the FunctionQuery and the full-text
query.


Thanks very much for your answers.

Regards, Sebastian

-- 
Sebastian Kirsch <skirsch@sebastian-kirsch.org> [http://www.sebastian-kirsch.org/]

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