Re: PG12 autovac issues

On Fri, Mar 27, 2020 at 08:23:03PM +0100, Julien Rouhaud wrote:
> FTR we reached the 200M transaxtion earlier, and I can see multiple logs of the
> form "automatic vacuum to prevent wraparound", so non-aggressive antiwraparound
> autovacuum, all on shared relations.

Thanks Julien for sharing the information with the community. Note
that three shared relations did not run such jobs though.

> As those vacuum weren't skipped, autovacuum didn't get stuck in a loop on those
> and continue its work normally. This happened ~ 4h ago, didn't ocurred again
> while the 200M threshold was reached again multiple time.

As we have confirmed that 2aa6e33 is actually the origin of the
problem, I am planning to revert it at the beginning of next week, and
then dig more into the origin of those anti-wraparound and
non-aggressive jobs happening for a portion of the shared relations.
Andres has started a thread about the problem on -hackers here:
https://www.postgresql.org/message-id/20200323235036.6pje6usrjjx22zv3@alap3.anarazel.de

And I'll follow up there with anything new I find. Please let me know
if there are any objections with the revert though, this will address
the problem reported by Justin.
--
Michael