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From Ype Kingma <>
Subject Re: MultiSearcher discards interim results
Date Tue, 11 Feb 2003 19:31:42 GMT

I tried to reply through a webmail facility earlier today, but it seems
to have failed. I'll try and provide a similar reply now. Please discard
the earlier attempt, if it gets through...

On Friday 07 February 2003 19:58, you wrote:
> I'm confused.  The contract of this method is to return the top-scoring
> nDocs.  For a multi-searcher it must compute the top-scoring nDocs from
> each sub-searcher, then find the top-scoring nDocs among these.  If you

For the first sub-searcher: yes. For the remaining sub-searchers it is only
necessary to collect docs with a score not smaller than the minimum
score provided by the first subsearcher.

In the worst case all the results of the remaining subsearchers will be
discarded anyway, so there is no point in collecting the best ndocs
for each of them, and in doing all the work in their priority queues.

The patch attempts to avoid this by using a single hit collector
with a single priority queue.

Some time ago I tried to implement a multi searcher and retriever
using the best ndocs from each subsearcher and discarding all
superfluous results. The real problem was that it would also retrieve
all documents before discarding them. Needless to say that I 
switched to a home brewn hit collector very soon. After collecting,
the retrieval is now done in order of document number per index reader.

As the new MultiSearcher also provides more consistent scoring
between subsearchers, I going to give it a try it asap.

I'd also like to try the new scoring explanation facilities.
Are there people using the nightly builds with some success?

Kind regards,

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