Re: [GENERAL] Creation of tsearch2 index is very slow - Mailing list pgsql-performance

From Oleg Bartunov
Subject Re: [GENERAL] Creation of tsearch2 index is very slow
Date
Msg-id Pine.GSO.4.63.0601211619541.14417@ra.sai.msu.su
Whole thread Raw
In response to Re: [GENERAL] Creation of tsearch2 index is very slow  (Martijn van Oosterhout)
Responses Re: [GENERAL] Creation of tsearch2 index is very slow  (Martijn van Oosterhout)
List pgsql-performance
On Sat, 21 Jan 2006, Martijn van Oosterhout wrote:

> However, IMHO, this algorithm is optimising the wrong thing. It
> shouldn't be trying to split into sets that are far apart, it should be
> trying to split into sets that minimize the number of set bits (ie
> distance from zero), since that's what's will speed up searching.

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:)

> 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 :)

     Regards,
         Oleg
_____________________________________________________________
Oleg Bartunov, Research Scientist, Head of AstroNet (www.astronet.ru),
Sternberg Astronomical Institute, Moscow University, Russia
Internet: , http://www.sai.msu.su/~megera/
phone: +007(495)939-16-83, +007(495)939-23-83

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