Re: VACUUMs take twice as long across all nodes

Am Sonntag, den 29.10.2006, 10:34 -0500 schrieb Andrew Sullivan:
> 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.

Actually, you need to get the schema from the master node, and can take
the data from a slave. In mixing dumps like that, you must realize that
there are two seperate parts in the schema dump: "table definitions" and
"constraints". Do get a restorable backup you need to put the table
definitions stuff before your data, and the constraints after the data
copy.

Andreas

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