Re: please explain vacuum with WAL

From: "Albe Laurenz" <laurenz(dot)albe(at)wien(dot)gv(dot)at>
To: "Dmitry Melekhov *EXTERN*" <dm(at)belkam(dot)com>, <pgsql-general(at)postgresql(dot)org>
Subject: Re: please explain vacuum with WAL
Date: 2008-07-08 11:33:29
Message-ID: D960CB61B694CF459DCFB4B0128514C2024B0A80@exadv11.host.magwien.gv.at
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Dmitry Melekhov wrote:
> I tried to ask this question in novice list.
> Just because there are no replies I try here.
> This is really novice question- I'm oracle dba :-)
>
> > I just installed 8.3 with WAL enabled.
> > But I can't understand why postgres generated many archive logs during
> > vacuum, if WAL is enabled.
> > Could you explain?

VACUUM changes the database, and these changes go to the transaction log.

If VACUUM changes a lot, you can end up with many archived WAL files.

There's no correspondence in Oracle, but think of it as an
"ALTER TABLE <name> MOVE" except that there is no NOLOGGING clause.

Yours,
Laurenz Albe

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