Re: tsearch2/GIST performance factors?

Craig,

could you prepare excerption from your db (if possible), so I could
play myself ?

     Oleg
On Mon, 17 Oct 2005, Craig A. James wrote:

> Oleg wrote:
>> Did you consider *decreasing* SIGLENINT ? Size of index will diminish
>> and performance could be increased. I use in current project SIGLENINT=15
>
> The default value for SIGLENINT actually didn't work at all.  It was only by
> increasing it that I got any performance at all.  An examination of the GIST
> indexes showed that most of the first level and many of the second level
> bitmaps were saturated.
>
>> tsearch2's index is a lossy index, read
>> http://www.sai.msu.su/~megera/oddmuse/index.cgi/Tsearch_V2_internals
>> so search results  should be rechecked !
>
> Yes, thanks.  We do indeed recheck the actual results.  The tests I'm running
> are just on the raw index performance - how long does it take to "select ...
> where dockeys @@ to_tsquery(...)".
>
>> We have our TODO http://www.sai.msu.su/~megera/oddmuse/index.cgi/todo
>> and hope to find sponsorhips for fts project for 8.2 release.
>> Unfortunately, I didn't find spare time to package tsearchd for you,
>> it should certainly help you.
>
> At this point we may not have time to try tsearchd, and unfortunately we're
> not in a position to sponsor anything yet.
>
> My original question is still bothering me.  Is it normal for a keyword that
> occurs in more than about 2% of the documents to cause such inconsistent
> performance?  Is there any single thing I might look at that would help
> improve performance (like, do I need more memory?  More shared memory?
> Different config parameters?)
>
> Thanks,
> Craig
>

     Regards,
         Oleg
_____________________________________________________________
Oleg Bartunov, sci.researcher, hostmaster of AstroNet,
Sternberg Astronomical Institute, Moscow University (Russia)
Internet: oleg@sai.msu.su, http://www.sai.msu.su/~megera/
phone: +007(095)939-16-83, +007(095)939-23-83