Re: Proposal: Log inability to lock pages during vacuum

On 2014-11-06 23:40:18 +0000, Greg Stark wrote:
> On Thu, Nov 6, 2014 at 9:30 PM, Andres Freund <andres(at)2ndquadrant(dot)com> wrote:
> > I think the retry logical is a largely pointless complication of already
> > complex enough code. You're fixing a problem for which there is
> > absolutely no evidence of its existance. Yes, this happens
> > occasionally. But it's going to be so absolutely minor in comparison to
> > just about every other source of bloat.
>
> I agree bloat isn't really a threat, but what about the relfrozenxid?
> If we skip even one page we don't get to advance it and retrying could
> eliminate those skipped pages and allow us to avoid a vacuum freeze
> which can be really painful. Of course that only works if you can be
> sure you haven't overflowed and forgotten any skipped pages and if you
> don't find the page still pinned every time until you eventually give
> up on it.

I don't buy this argument. Either you're constantly vacuuming the whole
relation anyway - in which case we'll acquire the cleanup lock
unconditionally - or we're doing partial vacuums via the visibility map
anyway.

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
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