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

On 2015-06-05 14:33:12 -0400, Tom Lane wrote:
> Robert Haas <robertmhaas(at)gmail(dot)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 think we might want to try to fix one or both of those before
> > cutting a new release. I'm less sold on the idea of installing
> > WAL-logging in this minor release. That probably needs to be done,
> > but right now we've got stuff that worked in early 9.3.X release and
> > is now broken, and I'm in favor of fixing that first.

I've implemented this, and so far it removes more code than it
adds. It's imo also a pretty clear win in how understandable the code
is. The remaining work, besides testing, is primarily going over lots
of comment and updating them. Some of them are outdated by the patch,
and some already were.

Will post tonight, together with the other fixes, after I get back from
climbing.

My gut feeling right now is that it's a significant improvement, and
that it'll be reasonable to include it. But I'd definitely like some
independent testing for it, and I'm not sure if that's doable in time
for the wrap.

> Okay, but if we're not committing today to a release wrap on Monday,
> I don't see it happening till after PGCon.

I wonder if, with all the recent, err, training, we could wrap it on
Tuesday instead. Independent of the truncation rework going in or not,
an additional work day to go over all the changes and do some more
testing would be good from my POV.

Greetings,

Andres Freund