Re: Vacuum ERRORs out considering freezing dead tuples from before OldestXmin - Mailing list pgsql-hackers

On Mon, Jun 24, 2024 at 1:05 PM Robert Haas <robertmhaas@gmail.com> wrote:
> On Mon, Jun 24, 2024 at 12:43 PM Peter Geoghegan <pg@bowt.ie> wrote:
> > The problem here is that OldestXmin is supposed to be more
> > conservative than vistest, which it almost always is, except in this
> > one edge case. I don't think that plugging that hole changes the basic
> > fact that there is one source of truth about what *needs* to be
> > pruned. There is such a source of truth: OldestXmin.
>
> Well, another approach could be to make it so that OldestXmin actually
> is always more conservative than vistest rather than almost always.

If we did things like that then it would still be necessary to write a
patch like the one Melanie came up with, on the grounds that we'd
really need to be paranoid about having missed some subtlety. We might
as well just rely on the mechanism directly. I just don't think that
it makes much difference.

--
Peter Geoghegan