Re: [doc patch] a slight VACUUM / VACUUM FULL doc improvement proposal

On Wed, May 16, 2007 at 12:09:26PM -0400, Alvaro Herrera wrote:
> Guillaume Cottenceau wrote:
> > "Jim C. Nasby" <decibel 'at' decibel.org> writes:
> >
> > > On Wed, May 16, 2007 at 09:41:46AM +0200, Guillaume Cottenceau wrote:
> >
> > [...]
> >
> > > > Come on, I don't suggest to remove several bold warnings about
> > > > it, the best one being "Therefore, frequently using VACUUM FULL
> > > > can have an extremely negative effect on the performance of
> > > > concurrent database queries." My point is to add the few
> > > > additional mentions; I don't think the claims that VACUUM FULL
> > > > physically compacts the data, and might be useful in case of too
> > > > long time with infrequent VACUUM are incorrect, are they?
> > >
> > > Unfortunately they are, to a degree. VACUUM FULL can create a
> > > substantial amount of churn in the indexes, resulting in bloated
> > > indexes. So often you have to REINDEX after you VACUUM FULL.
> >
> > Ok, VACUUM FULL does his job (it physically compacts the data and
> > might be useful in case of too long time with infrequent VACUUM),
> > but we are going to not talk about it because we often needs a
> > REINDEX after it? The natural conclusion would rather be to
> > document the fact than REINDEX is needed after VACUUM FULL, isn't
> > it?
>
> Maybe, but we should also mention that CLUSTER is a likely faster
> workaround.

What this boils down to is that there should probably be a separate
subsection that deals with "Oh noes! My tables are too big!"
--
Jim Nasby                                      decibel@decibel.org
EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)