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From Alan Woodward <a...@flax.co.uk>
Subject Re: Document scoring order?
Date Thu, 04 Apr 2013 08:28:45 GMT
Hi Otis,

It depends on the Scorer implementation.  The default iterates through matching documents
by calling nextDoc(), which just moves along the postings lists in-order, but you could roll
your own.  You're pretty constrained by the fact that the low-level DocIdSetIterators only
move forward though.

I'm experimenting with some out-of-order postings lists (for example, sorted by frequency)
to allow early search termination for disjunction queries, but this has its own drawbacks
- if postings lists for different terms are in different orders, then you can't use any Scorer
that calls advance().

The other thing to look at would be sorted segments, see https://issues.apache.org/jira/browse/LUCENE-4752.

Alan Woodward
www.flax.co.uk


On 4 Apr 2013, at 02:56, Otis Gospodnetic wrote:

> Hi,
> 
> When Lucene scores matching documents, what is the order in which
> documents are processed/scored and can that be changed?  I'm guessing
> it scores matches in whichever order they are stored in the index/on
> disk, which means by increasing docIDs?
> 
> I do see some out of order scoring is possible.... but can one visit
> docs to score in, say, lexicographical order of a specific document
> field?
> 
> Thanks,
> Otis
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