Re: PGSQL 7.4 -> 8.1 migration & performance problem

[Ludwig Isaac Lim <ludz_lim(at)yahoo(dot)com>]

Hi:

  Just a hunch:

  What about adding an index to the field
etapes_lignes_commandes(code_etape). Assuming your database
 uses C locales. This might work for your particular query
since your filter is something like code_etape~~'COMP%'.
What about increasing the settings of work_mem, etc (check
http://www.powerpostgresql.com/PerfList) .

ludwig.

--- Philippe Lang <philippe(dot)lang(at)attiksystem(dot)ch> wrote:

> Hi,
> 
> I have now disabled hyperthreading in /etc/grub.conf
> (added noht at the end
> of kernel lines), rebooted the server, run ANALYSE on the
> database again,
> and launched the query: things are even a little bit
> worse, it completes in
> 540 seconds now. So this is no ANALYSE or hyperthreading
> problem.
> 
> Here are both EXPLAIN ANALYSE results, plus the query
> itself:
> 
> Postgresql 7.4.5:
> http://www.attiksystem.ch/explain_analyze_74.txt
> 
> Postgresql 8.1.4:
> http://www.attiksystem.ch/explain_analyze_81.txt
> 
> Query is here: http://www.attiksystem.ch/big_query.txt
> 
> The freebsd box, as far as I can remember, has not been
> specifically tuned.
> I did recompile a kernel with a few things inside, but
> really, I did not
> spend hours on that two years ago.
> 
> Thanks,
> 
> Philippe
> 
> 
> -----Message d'origine-----
> De : Tom Lane [mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us] 
> Envoy&#65533;: mercredi, 31. mai 2006 16:39
> &#65533;: Philippe Lang
> Cc : pgsql-general(at)postgresql(dot)org
> Objet : Re: [GENERAL] PGSQL 7.4 -> 8.1 migration &
> performance problem 
> 
> "Philippe Lang" <philippe(dot)lang(at)attiksystem(dot)ch> writes:
> > http://www.attiksystem.ch/postgresql-general.txt
> 
> Please provide EXPLAIN ANALYZE, not just EXPLAIN, output
> ... and try to post
> it in an un-line-wrapped form.
> 
> Also, as Ludwig mentioned, a common gotcha is to forget
> to ANALYZE your data
> after moving it to a new database.
> 
> 			regards, tom lane
> 
> 


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