Re: Query plan changes after pg_dump / pg_restore

From: Dennis Bjorklund <db(at)zigo(dot)dhs(dot)org>
To: Jona <jonanews(at)oismail(dot)com>
Cc: Christopher Kings-Lynne <chriskl(at)familyhealth(dot)com(dot)au>, <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Query plan changes after pg_dump / pg_restore
Date: 2005-06-09 10:48:07
Message-ID: Pine.LNX.4.44.0506091244490.24742-100000@zigo.dhs.org
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On Thu, 9 Jun 2005, Jona wrote:

> It's the same (physical) server as well as the same PostGreSQL daemon,
> so yes.

The only thing that can differ then is the statistics collected and the
amount of dead space in tables and indexes (but since you both reindex and
run vacuum full that should not be it).

So comparing the statistics in the system tables is the only thing I can
think of that might bring some light on the issue. Maybe someone else have
some ideas.

And as KL said, the effective_cache_size looked like it was way to small.
With that setting bigger then pg should select index scans more often. It
doesn't explain why the databases behave like they do now, but it might
make pg select the same plan nevertheless.

--
/Dennis Björklund

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