Re: Snapshot too old logging

On Tue, Nov 15, 2016 at 7:43 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:

> On Tue, Nov 15, 2016 at 1:30 PM, Magnus Hagander <magnus(at)hagander(dot)net>
> wrote:
> > On Tue, Nov 15, 2016 at 7:27 PM, Robert Haas <robertmhaas(at)gmail(dot)com>
> wrote:
> >>
> >> On Tue, Nov 15, 2016 at 1:18 PM, Magnus Hagander <magnus(at)hagander(dot)net>
> >> wrote:
> >> > Is there value in showing which snapshot as well? Something like:
> >> > DETAIL: snapshot <xyz> is too old to access relation <relation>
> >>
> >> IIUC, the granularity is per-block, not per-relation, so that might be
> >> misleading.
> >
> > Does it help to let the user know which number? I'm not really sure what
> I'd
> > do with that information, whereas knowing the relation would be very
> useful.
> >
> > But we could certainly say "snapshot <xyz> is too old to access block
> <nnn>
> > of relation <rel>".
>
> I think it would be better not to include either the snapshot or the
> block number, and just find some way to reword the error message so
> that it mentions which relation was involved without implying that all
> access to the relation would necessarily fail. For example:
>
> ERROR: snapshot too old
> DETAIL: One or more rows required by this query have already been
> removed from "%s".
>
>
Sounds good to me. I've only really found use for the relation name so far
:)

How about the attached?

And if ppl are OK with it, thoughts on backpatching to 9.6?

--
Magnus Hagander
Me: http://www.hagander.net/
Work: http://www.redpill-linpro.com/