Re: autovacuum not freeing up unused space on 8.3.0

On Tue, Feb 26, 2008 at 3:11 PM, Stuart Brooks <stuartb(at)cat(dot)co(dot)za> wrote:
>
> >> ERROR: canceling autovacuum task
> >> CONTEXT: automatic vacuum of table "metadb.test.transactions"
> >
> > Are these happening regularly? They indicate that something is
> > happening on the table that collides with what autovacuum needs to do,
> > and autovacuum defers its task. For this to happen you need to be doing
> > ALTER TABLE or similar however; normal UPDATE/INSERT/DELETE should not
> > cause autovacuum to cancel itself.
> >
> I am not using an ALTER table command but I am doing periodic ANALYZEs
> to evaluate the table size. Could this be causing the problem? I notice
> that stopping the ANALYZE calls appears to eliminate the canceled
> autovacuum.
>

I am trying to reproduce the case here, but could not. Can you post the table
schema and the operations you are carrying out ? Is it just INSERT new rows
and DELETE old rows or are there any UPDATEs too ? Are there any long
running transactions open ?

> What concerns me is that once the size has grown, even a VACUUM FULL
> doesn't recover the space. Regular external VACUUMs keep the table at
> around 10MB but if I use autovacuum and it grows to 40MB, a VACUUM FULL
> will only get it down to 35MB. Is it possible that a canceled autovacuum
> could result in permanently lost space?
>

AFAIK it should not. Can you also post VACUUM FULL VERBOSE output ?

Thanks,
Pavan

--
Pavan Deolasee
EnterpriseDB http://www.enterprisedb.com