Re: Have vacuum emit a warning when it runs out of maintenance_work_mem

On Fri, May 11, 2007 at 10:18:30PM -0400, Robert Treat wrote:
> On Wednesday 09 May 2007 19:41, Guillaume Smet wrote:
> > On 5/9/07, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> > > Jim Nasby <decibel@decibel.org> writes:
> > > > Any time this happens it's generally a nasty surprise for users.
> > >
> > > Really?  Running out of work memory is expected on large tables.
> >
> > Sure. Perhaps we should find a better error message but it's an
> > interesting information. Personnaly, I try to choose a sane value
> > depending on my database but I'm never sure it's really sufficient or
> > if I added 100MB it would have made a real difference.

Unfortunately, a lot of users aren't as knowledgeable as folks here,
that's why I made it a warning and gave it a hint. But if people think
that's too high a level we can change it to something lower...

> If we were going to implement this (and I'm a tad skeptical as well), wouldn't
> it be better if the warning occured at the end of vacuum, and told you how
> much memory was actually needed, so you'd know what maintainence_work_mem
> should be.

Maybe... the problem is that for really large tables you simply won't
have a choice; it will have to fall to disk. So I think we'd have to
keep per-table warnings, unless you've got an idea for how we could
account for tables that wouldn't reasonably fit?
--
Jim Nasby                                            jim@nasby.net
EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)