Re: autovacuum blues

On Thu, 2006-11-09 at 18:16 +0100, Anton Melser wrote:
> On 09/11/06, Alvaro Herrera <alvherre(at)commandprompt(dot)com> wrote:
> > Anton Melser wrote:
> > > Hi,
> > > I just can't understand why autovacuum is not working. I have a test
> > > db/table which I insert values into (by the thousands) and can't work
> > > out why my stats don't get updated. Could someone have a quick look at
> > > my attached .conf and tell me what I am doing?
> > > I am running it on FC5 8.1.4.fc5.1.
> >
> > You can tell whether autovacuum is running by using
> >
> > SHOW autovacuum;
> >
> >
> > Note that if you have a firewall of some sort stopping UDP messages from
> > being transmitted inside your machine, the stats collector may not
> > start, which may stop the autovacuum daemon from starting. If you're
> > not seeing stat updates then there's probably something like that going
> > on. Maybe the system has emitted a warning message at server start;
> > check the logs.
>
> Thanks for that. Just a clarification, can someone tell me what the
> "number of tuples" means in the context of the multipliers? I mean,
> when the vacuum min multiplier is at 0.4, we multiply 0.4 by what? I
> get the min val, but what are we multiplying by 0.4? The total number
> of tuples in the table? The total modified/deleted?

http://www.postgresql.org/docs/8.1/static/runtime-config-autovacuum.html

I read that to mean that it multiplies the total number of tuples in the
table by autovacuum_vacuum_scale_factor and adds the
autovacuum_vacuum_threshold to that number. If the number of
updated/deleted tuples exceeds that sum, autovacuum will issue a vacuum.

The docs could maybe be more clear on this.

Regards,
Jeff Davis