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From liat oren <oren.l...@gmail.com>
Subject Re: Getting a score of a specific document
Date Mon, 18 May 2009 06:55:38 GMT
Sorry I didn't explain myself well.

The problem I try to address is the following:
Think about the case where you have 100,000 documents indexed. Take word 'a'
- if it appears in 80,000 documents, you want the score to take it into
account. You want only to see how 20,000 documents are close to a query, and
only 10,000 of these contain the word 'a'.
80,000 / 100,000 (the 'statistics' of the whole index) is much smaller than
10,000 / 20,000 (the 'statistics of only the group of documents). So it does
affect the score if I use the whole index or just the documents I am
interested in.
It might be that the order of these desired documents will not change, but I
don;t see how you can assure it since the idf value can be really different.

So, I want the documents for my query to be
ranked *relative to each other*, AND NOT restricted to only the documents
I care about.
For that case, I need to use the filter, right?

Its fine if I get the results in DocumentID - then I open these using
IndexReader to get the fields I need.

Could you please give me an example of how I creat the Filter that filters
out a given list of ids?

Thanks!
Liat
2009/5/18 Erick Erickson <erickerickson@gmail.com>

> I'm still unclear what you want the statistics *for*. "statistics"
> are pretty meaningless as far as I understand. The whole point
> of scoring is to use various "statistics" to *rank* documents *for
> a specific query*. You cannot, for instance, compare scores
> between different queries in any meaningful way.
>
> If you're saying that you want the documents for your query to be
> ranked *relative to each other*, but restricted to only the documents
> you care about, then I think you need a HitCollector
> because a Filter (last I knew) doesn't score documents therefore
> won't order them.
>
> But asking if the statistics reflect the whole index just isn't making any
> sense to me. If you're asking that question I suspect that there's
> something about your problem space I don't understand and
> you're not explaining simply enough for me to grasp <G>.
>
> So forget a Filter because you'll get the documents back in
> (probably, but my memory is weak some days) document ID
> order. Implement a HitCollector whose collect method only
> sets bits for docs in your list. See:
>
> http://lucene.apache.org/java/2_2_0/api/org/apache/lucene/search/HitCollector.html#collect(int,%20float)
>
> Best
> Erick
>
>
> On Sun, May 17, 2009 at 3:57 AM, liat oren <oren.liat@gmail.com> wrote:
>
> > Yes, this is what I need - I don't need to get the scores for the
> documents
> > that were filtered.
> > The statistics I ment are idf(t) for example.
> > I want these to include the whole index of course.
> > It will include this info of all the index, right?
> >
> > if I have a list of ids that the query should look at, which Filter
> should
> > I
> > use?
> >
> > Thanks a lot,
> > Liat
> >
> > 2009/5/14 Erick Erickson <erickerickson@gmail.com>
> >
> > > Hmmm, come to think of it, if you pass the Filter to the search
> I*think*
> > > you
> > > don't get scores for that clause, but you may want to
> > > check it out...
> > >
> > > So I think you should think about implementing a HitCollector
> > > and collect only the documents you care about.
> > >
> > > This is really very little extra work since all the documents have
> > > to be evaluated anyway.
> > >
> > > I'm not sure what you mean by statistics for the whole index. I suspect
> > > you're wondering if the scores reflect all the documents. But you don't
> > > care because scores are not relevant between different queries, and
> > > if they are calculated only within the query you're running, all the
> > > documents returned have scores that rank them relative to each other.
> > >
> > > Best
> > > Erick
> > >
> > > On Thu, May 14, 2009 at 9:16 AM, liat oren <oren.liat@gmail.com>
> wrote:
> > >
> > > > Yes, I have a pre-defined list of documents that I care about.
> > > > Then I can do the search on these, but it will take the statictics of
> > the
> > > > whole index, right?
> > > >
> > > >
> > > >
> > > >
> > > > 2009/5/14 Erick Erickson <erickerickson@gmail.com>
> > > >
> > > > > I don't know if I'm understanding what you want, but if you havea
> > > > > pre-defined list of documents, couldn't you form a Filter? Then
> > > > > your results would only be the documents you care about.
> > > > >
> > > > > If this is irrelevant, perhaps you could explain a bit more about
> > > > > the problem you're trying to solve.
> > > > >
> > > > > Best
> > > > > Erick
> > > > >
> > > > > On Thu, May 14, 2009 at 5:03 AM, liat oren <oren.liat@gmail.com>
> > > wrote:
> > > > >
> > > > > > Hi,
> > > > > >
> > > > > > I have a big index and I want to get for a specific search only
> the
> > > > > grades
> > > > > > of a list of documents.
> > > > > > Is there a better way to get this score than looping on all
the
> > > > reasults
> > > > > > set?
> > > > > >
> > > > > > Thanks,
> > > > > > Liat
> > > > > >
> > > > >
> > > >
> > >
> >
>

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