From: | Martijn van Oosterhout <kleptog(at)svana(dot)org> |
---|---|
To: | Oleg Bartunov <oleg(at)sai(dot)msu(dot)su> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Ron <rjpeace(at)earthlink(dot)net>, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: [GENERAL] Creation of tsearch2 index is very slow |
Date: | 2006-01-21 15:04:24 |
Message-ID: | 20060121150424.GB9955@svana.org |
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Lists: | pgsql-general pgsql-performance |
On Sat, Jan 21, 2006 at 04:29:13PM +0300, Oleg Bartunov wrote:
> Martijn, you're right! We want not only to split page to very
> different parts, but not to increase the number of sets bits in
> resulted signatures, which are union (OR'ed) of all signatures
> in part. We need not only fast index creation (thanks, Tom !),
> but a better index. Some information is available here
> http://www.sai.msu.su/~megera/oddmuse/index.cgi/Tsearch_V2_internals
> There are should be more detailed document, but I don't remember where:)
I see how it works, what I don't quite get is whether the "inverted
index" you refer to is what we're working with here, or just what's in
tsearchd?
> >That's harder though (this algorithm does approximate it sort of)
> >and I havn't come up with an algorithm yet
>
> Don't ask how hard we thought :)
Well, looking at how other people are struggling with it, it's
definitly a Hard Problem. One thing though, I don't think the picksplit
algorithm as is really requires you to strictly have the longest
distance, just something reasonably long. So I think the alternate
algorithm I posted should produce equivalent results. No idea how to
test it though...
Have a nice day,
--
Martijn van Oosterhout <kleptog(at)svana(dot)org> http://svana.org/kleptog/
> Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a
> tool for doing 5% of the work and then sitting around waiting for someone
> else to do the other 95% so you can sue them.
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