Re: [GENERAL] 9.4.1 -> 9.4.2 problem: could not access status of transaction 1

On 2015-06-05 20:47:33 +0200, Andres Freund wrote:
> On 2015-06-05 14:33:12 -0400, Tom Lane wrote:
> > Robert Haas <robertmhaas@gmail.com> writes:
> > > 1. The problem that we might truncate an SLRU members page away when
> > > it's in the buffers, but not drop it from the buffers, leading to a
> > > failure when we try to write it later.
>
> I've got a fix for this, and about three other issues I found during
> development of the new truncation codepath.
>
> I'll commit the fix tomorrow.

I've looked through multixact.c/slru.c and afaics there currently is, as
observed by Thomas, no codepath that exercises the broken behaviour. Due
to the way checkpoints and SLRU truncation are linked "problematic"
pages will have been flushed beforehand.

I think we should fix this either way as it seems like a bad trap, but
I'd rather commit it after the the next minor releases are out.