Re: slow query

On Mon, 2003-02-24 at 12:27, Clarence Gardner wrote:
> On 24 Feb 2003, Robert Treat wrote:
>
> >
> > If your seeing wildly dramatic improvments from vacuum full, you might
> > want to look into running regular vacuums more often (especially for
> > high turnover tables), increase your max_fsm_relations to 1000, and
> > increasing your max_fsm_pages.
>
> I don't know about the settings you mention, but a frequent vacuum
> does not at all obviate a vacuum full. My database is vacuumed every
> night, but a while ago I found that a vacuum full changed a simple
> single-table query from well over 30 seconds to one or two. We now
> do a vacuum full every night.

Sure is does.  If your free-space-map (FSM) is up to date, tuples are
not appended to the end of the table, so table growth will not occur
(beyond a 'settling' point.

Unless you remove more data from the table than you ever expect to have
in the table again, this is enough.  That said, the instant the FSM is
empty, you're table starts to grow again and a VACUUM FULL will be
required to re-shrink it.

--
Rod Taylor <rbt@rbt.ca>

PGP Key: http://www.rbt.ca/rbtpub.asc