Re: PGSQL 7.4 -> 8.1 migration & performance problem

["Philippe Lang" <philippe(dot)lang(at)attiksystem(dot)ch>]

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] 
Envoyé : mercredi, 31. mai 2006 16:39
À : 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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