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Re: perf pb solved only after pg_dump and restore

From: Markus Schaber <schabi(at)logix-tt(dot)com>
To: Guillaume Cottenceau <gc(at)mnc(dot)ch>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: perf pb solved only after pg_dump and restore
Date: 2006-08-28 09:28:23
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
Hi, Guillaume

Guillaume Cottenceau wrote:

> We noticed a slowdown on our application while traffic was kinda
> heavy. The logics after reading the docs commanded us to trim the
> enlarged tables, run VACUUM ANALYZE and then expect fast
> performance again; but it wasn't the case[1].

What exactly do you mean with "trim the enlarged tables"?

> Out of the blue, we dumped the database, removed it, recreated
> from the restore, and now the performance is lightning fast
> again.
> Does it look familiar to anyone? I thought running VACUUM ANALYZE
> after a trim should be enough so that pg has assembled the data
> and has good statistical knowledge of the tables contents..

This looks like either your free_space_map setting is way to low, or you
have index bloat.

Maybe a VACUUM FULL fullowed by a REINDEX will have solved your problem.

It also might make sense to issue a CLUSTER instead (which combines the
effects of VACUUM FULL, REINDEX and physically reordering the data).

When the free_space_map is to low, VACUUM ANALYZE should have told you
via a warning (at least, if your logging is set appropriately).

Markus Schaber | Logical Tracking&Tracing International AG
Dipl. Inf.     | Software Development GIS

Fight against software patents in EU!

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