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From Erick Erickson <erickerick...@gmail.com>
Subject Re: queryNorm affect on score
Date Mon, 02 Mar 2009 02:27:18 GMT
FWIW, Hossman pointed out that the difference between index and
query time boosts is that index time boosts on title, for instance,
express "I care about this document's title more than other documents'
titles [when it matches]" Query time boosts express "I care about matches
on the title field more than matches on other fields".

Best
Erick

On Sun, Mar 1, 2009 at 8:57 PM, Peter Keegan <peterlkeegan@gmail.com> wrote:

> As suggested, I added a query-time boost of 0.0f to the 'literals' field
> (with index-time boost still there) and I did get the same scores for both
> queries :)  (there is a subtlety between index-time and query-time boosting
> that I missed.)
>
> I also tried disabling the coord factor, but that had no affect on the
> score, when combined with the above. This seems ok in this example since
> the
> the matching terms had boost = 0.
>
> Thanks Yonik,
> Peter
>
>
>
> On Sat, Feb 28, 2009 at 6:02 PM, Yonik Seeley <yonik@lucidimagination.com
> >wrote:
>
> > On Sat, Feb 28, 2009 at 3:02 PM, Peter Keegan <peterlkeegan@gmail.com>
> > wrote:
> > >> in situations where you  deal with simple query types, and matching
> > query
> > > structures, the queryNorm
> > >> *can* be used to make scores semi-comparable.
> > >
> > > Hmm. My example used matching query structures. The only difference was
> a
> > > single term in a field with zero weight that didn't exist in the
> matching
> > > document. But one score was 3X the other.
> >
> > But the zero boost was an index-time boost, and the queryNorm takes
> > into account query-time boosts and idfs.  You might get closer to what
> > you expect with a query time boost of 0.0f
> >
> > The other thing affecting the score is the coord factor - the fact
> > that fewer of the optional terms matched (1/2) lowers the score.  The
> > coordination factor can be disabled on any BooleanQuery.
> >
> > If you do both of the above, I *think* you would get the same scores
> > for this specific example.
> >
> > -Yonik
> > http://www.lucidimagination.com
> >
> > ---------------------------------------------------------------------
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> >
> >
>

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