Date: Sun, 29 Oct 2006 10:34:04 -0500
From: Andrew Sullivan <ajs@crankycanuck.ca>
To: pgsql-performance@postgresql.org
Subject: Re: VACUUMs take twice as long across all nodes
Message-ID: <20061029153404.GF14585@phlogiston.dyndns.org>
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On Sun, Oct 29, 2006 at 03:08:26PM +0000, Gavin Hamill wrote:
> 
> This is interesting, but I don't understand.. We've done a full restore
> from one of these pg_dump backups before now and it worked just great.
> 
> Sure I had to DROP SCHEMA _replication CASCADE to clear out all the
> slony-specific triggers etc., but the new-master ran fine, as did
> firing up new replication to the other nodes :)
> 
> Was I just lucky?

Yes.  Slony alters data in the system catalog for a number of
database objects on the replicas.  It does this in order to prevent,
for example, triggers from firing both on the origin and the replica. 
(That is the one that usually bites people hardest, but IIRC it's not
the only such hack in there.)  This was a bit of a dirty hack that
was supposed to be cleaned up, but that hasn't been yet.  In general,
you can't rely on a pg_dump of a replica giving you a dump that, when
restored, actually works.

A

-- 
Andrew Sullivan  | ajs@crankycanuck.ca
Everything that happens in the world happens at some place.
		--Jane Jacobs