Re: db size and VACUUM ANALYZE

On Fri, Feb 12, 2010 at 10:40 PM, Marcin Krol <mrkafk(at)gmail(dot)com> wrote:

> Hello,
>
> The db in the application I maintain but didn't write (it obviously
> makes use of PG, v 8.3), has been systematically growing in size from
> about 600M to 1.6G.
>
> At the same time, the performance of the app has degraded significantly
> (several times).
>
> So I've done VACUUM ANALYZE on entire db. Nothing. The db did not
> decrease in size, the performance stayed the same.
>
> So I backed it up using pg_dump, deleted database, and recreated it from
> backup.
>
> The size of db on disk went down to 600M, performance recovered to the
> original level.
>
> Why that is so? I thought that VACUUM ANALYZE does everything that is
> needed to optimize disk usage?
>
> Regards,
> mk
>
>

You need to do VACUUM FULL ANALYZE to claim the disk space, but this creates
a exclusive lock on the tables.

See http://www.postgresql.org/docs/8.3/static/sql-vacuum.html

With regards

Amitabh Kant