Re: 10RC1 crash testing MultiXact oddity

Jeff Janes wrote:
> On Fri, Sep 22, 2017 at 1:19 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>
> > On Fri, Sep 22, 2017 at 3:39 PM, Jeff Janes <jeff(dot)janes(at)gmail(dot)com> wrote:
> > > It turns out it is not new in pg10. I spotted in the log file only by
> > > accident while looking for something else. Now that I am looking for
> > it, I
> > > do see it in 9.6 as well.
> >
> > So I guess the next question is whether it also shows up if you initdb
> > with 9.4.latest and then run the same test.
> >
>
> git bisect shows that it shows up in 9.5, at this commit:
>
> commit bd7c348d83a4576163b635010e49dbcac7126f01
> Author: Andres Freund <andres(at)anarazel(dot)de>
> Date: Sat Sep 26 19:04:25 2015 +0200
>
> Rework the way multixact truncations work.

Oh man. And I thought we were done with that stuff :-(

> Not really sure what the next step is here. I could promote the
> ereport(LOG...) to a PANIC to get a core dump, but I don't think that would
> help because presumably the problem occurred early, when the truncation was
> done, not when it was detected.

Probably the best way to track it down is to add some instrumentation
elog(LOG) to the multixact truncation mechanism.

--
Álvaro Herrera https://www.2ndQuadrant.com/
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