On Thu, 2007-10-25 at 13:51 -0400, Andrew Dunstan wrote:
>
> Michael Paesold wrote:
> > In the previous discussion, Simon and me agreed that schema changes
> > should not happen on a regular basis on production systems.
> >
> > Shouldn't we rather support the regular usage pattern instead of the
> > uncommon one? Users doing a lot of schema changes are the ones who
> > should have to work around issues, not those using a DBMS sanely. No?
> >
> Unfortunately, doing lots of schema changes is a very common phenomenon.
> It makes me uncomfortable too, but saying that those who do it have to
> work around issues isn't acceptable IMNSHO - it's far too widely done.
We didn't agree that DDL was uncommon, we agreed that running DDL was
more important than running an auto VACUUM. DDL runs very quickly,
unless blocked, though holds up everybody else. So you must run it at
pre-planned windows. VACUUMs can run at any time, so a autoVACUUM
shouldn't be allowed to prevent DDL from running. The queuing DDL makes
other requests queue behind it, even ones that would normally have been
able to execute at same time as the VACUUM.
Anyway, we covered all this before. I started off saying we shouldn't do
this and Heikki and Michael came up with convincing arguments, for me,
so now I think we should allow autovacuums to be cancelled.
--
Simon Riggs
2ndQuadrant http://www.2ndQuadrant.com