Re: BUG #5322: Time to perform vacuums

On Wed, Feb 10, 2010 at 8:56 AM, Eric Pailleau <eric(at)numlog(dot)fr> wrote:
>
> The following bug has been logged online:
>
> Bug reference:      5322
> Logged by:          Eric Pailleau
> Email address:      eric(at)numlog(dot)fr
> PostgreSQL version: 8.2.3
> Operating system:   linux debian
> Description:        Time to perform vacuums
> Details:
>
> Hello,
> I really don't know if it can be a bug or not,
> but when I do a 'VACCUM FULL ANALYZE VERBOSE',
> it can take a very long time (expecially on large tables), while doing this
> sequence of 3 commands is
> quite quicker (on my system at least).
>
> VACCUM VERBOSE
> then
> VACCUM FULL VERBOSE
> then
> VACCUM FULL ANALYZE VERBOSE
>
> I mean adding the 'three commands' times is less than the time for the
> direct 'VACCUM FULL ANALYZE VERBOSE'.
>
> Does the fact of doing a 'simple' VACUUM first, make
> other VACCUM more quick ? Does it finally does the same ? Is it only
> coincidence due to system load ?
>
> Thanks for your comments about this...

I can see VACUUM making VACUUM FULL faster. I don't think VACUUM FULL
should make VACUUM FULL ANALYZE faster.

It's a known problem that VACUUM FULL is really slow. CLUSTER is
usually a better alternative; and in the next major release of
PostgreSQL VACUUM FULL will switch over to using approximately the
same method that CLUSTER now does.

...Robert