Re: 10RC1 crash testing MultiXact oddity

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.

The patches which enable the crashes and the rapid consumption of xid and
multixact both need a little adjustment from the 10rc1 versions, so I'm
attaching a combined patch that applies to bd7c348d83.

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.

Cheers,

Jeff