Bruce Momjian wrote:
> On Wed, Apr 22, 2015 at 04:36:17PM +0100, Greg Stark wrote:
> > On Mon, Apr 20, 2015 at 8:48 PM, Bruce Momjian <bruce@momjian.us> wrote:
> > > Well, we have to assume there are many misconfigured configurations ---
> > > autovacuum isn't super-easy to configure, so we can't just blame the
> > > user if this makes things worse. In fact, page pruning was designed
> > > spefically for cases where autovacuum wasn't running our couldn't keep
> > > up.
> >
> > Well autovacuum isn't currently considering HOT pruning part of its
> > job at all. It's hard to call it "misconfigured" when there's
> > literally *no* way to configure it "correctly".
>
> Good point, but doesn't vacuum remove the need for pruning as it removes
> all the old rows?
Sure. The point, I think, is to make autovacuum runs of some sort that
don't actually vacuum but only do HOT-pruning. Maybe this is a
reasonable solution to the problem that queries don't prune anymore
after Simon's patch. If we made autovac HOT-prune periodically, we
could have read-only queries prune only already-dirty pages. Of course,
that would need further adjustments to default number of autovac
workers, I/O allocation, etc.
--
Álvaro Herrera http://www.2ndQuadrant.com/
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