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Date: Sat, 5 Nov 2011 12:09:11 -0400
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Subject: Re: Comparing apples & oranges?
From: Erick Erickson <erickerickson@gmail.com>
To: solr-user@lucene.apache.org
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What about Function Queries? They can essentially take field values
and use them as part of the score calculations....

Best
Erick

On Fri, Nov 4, 2011 at 6:28 AM, Martin Koch <mak@issuu.com> wrote:
> Hi List
>
> I have a solr index where I want to include numerical fields in my rankin=
g
> function as well as keyword relevance. For example, each document has a
> document view count, and I'd like to increase the relevancy of documents
> that are read often, and penalize documents with a very low view count. I=
'm
> aware that this could be achieved with a filter as well, but ignore that
> for this question :) since this will be extended to other numerical field=
s.
>
> The keyword scoring works just fine and I can include the view count as a
> factor in the scoring, but I would like to somehow express that the view
> count accounts for e.g. 25% of the total score. This could be achieved by
> mapping the view count into some predetermined fixed range and then
> performing suitable arithmetic to scale to the score of the query. The
> score of the term query is normalized to queryNorm, so I'd like somehow t=
o
> express that the view count score should be normalized to the queryNorm.
>
> If I look at the explain of how the score below is computed, the 17.4 is
> the part of the score that comes from term relevancy. Searching for anoth=
er
> (set of) terms yields a different queryNorm, so I can't see how I can
> a-priori pick a scaling function (I've used log for this example) and boo=
st
> factor that will give control of the final contribution of the view count
> to the score.
>
> 19.14161 =3D (MATCH) sum of:
> =A017.403849 =3D (MATCH) max plus 0.1 times others of:
> =A0 =A016.747877 =3D (MATCH) weight(document:water^4.0 in 1076362), produ=
ct of:
> =A0 =A0 =A00.22298127 =3D queryWeight(document:water^4.0), product of:
> =A0 =A0 =A0 =A04.0 =3D boost
> =A0 =A0 =A0 =A02.939238 =3D idf(docFreq=3D527730, maxDocs=3D3669552)
> =A0 =A0 =A0 =A00.018965907 =3D queryNorm
> =A0 =A0 =A075.108894 =3D (MATCH) fieldWeight(document:water in 1076362), =
product
> of:
> =A0 =A0 =A0 =A025.553865 =3D tf(termFreq(document:water)=3D653)
> =A0 =A0 =A0 =A02.939238 =3D idf(docFreq=3D527730, maxDocs=3D3669552)
> =A0 =A0 =A0 =A01.0 =3D fieldNorm(field=3Ddocument, doc=3D1076362)
> [snip]
> =A01.7377597 =3D (MATCH) FunctionQuery(log(map(int(views),0.0,0.0,1.0))),
> product of:
> =A0 =A01.8325089 =3D log(map(int(views)=3D68,min=3D0.0,max=3D0.0,target=
=3D1.0))
> =A0 =A050.0 =3D boost
> =A0 =A00.018965907 =3D queryNorm
>
> Thanks in advance for your help,
> /Martin
>