Re: Autovacuum in the backend

On Thu, Jun 16, 2005 at 11:07:31AM +1000, Gavin Sherry wrote:
> On Wed, 15 Jun 2005, Bruce Momjian wrote:
>
> > I am going to start working on it. I am concerned it is a big job.
> >
> > I will post questions as I find them, and the one below is a good one.
>
> I'm wondering if effort is being misdirected here. I remember when Mark
> Wong at OSDL was running pg_autovacuum during a dbt run, he was seeing
> significant performance loss -- I think on the order of 30% to 40% (I will
> try and dig up a link to the results).

I think those are orthogonal issues. One is fixing whatever performance
issues there are because of VACUUM. Note that the fact that Mark was
having such a drop in performance with autovacuum does only mean that
at the enormous load under which the OSDL tests are run, autovacuum is
not the best solution. Not everybody runs with that sort of load
anyway. (In fact lots of people don't.)

So, one issue is that at high loads, there are improvements to be made
to VACUUM. The other issue is to get VACUUM to run in the first place,
which is what autovacuum addresses.

I can easily predict that we will make adjustments and improvements to
VACUUM in the future, but I'm not so sure if it will happen before 8.1
feature-freezes. I have more confidence that we can integrate
autovacuum for 8.1, which will be a leap forward.

--
Alvaro Herrera (<alvherre[a]surnet.cl>)
"Pido que me den el Nobel por razones humanitarias" (Nicanor Parra)