Re: Postgresql performance degrading... how to diagnose the root cause

Le 29/03/2013 15:20, Franck Routier a écrit :
> Hi,
>
> I have a postgresql database (8.4) running in production whose
> performance is degrading.
> There is no single query that underperforms, all queries do.
> Another interesting point is that a generic performance test
> (https://launchpad.net/tpc-b) gives mediocre peformance when run on
> the database, BUT the same test on a newly created database, on the
> same pg cluster, on the same tablespace, does perform good.
>
> So the problem seems to be limited to this database, even on newly
> created tables...
>
> What should I check to find the culprit of this degrading performance ?
>
> Franck
>
Just for the record, the problem turned out to be a too high
default_statistics_target (4000) that was causing the planner to take up
to seconds just to evaluate the better plan (probably in eqjoinsel() ).
See thread titled "What happens between end of explain analyze and end
of query execution ?" on this list for details.

Thanks again to those who responded.

Franck