Re: Vacuum ERRORs out considering freezing dead tuples from before OldestXmin

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.

I agree with you that letting the pruning horizon move forward during
vacuum is desirable. I'm just wondering if having the vacuum code need
to know a second horizon is really the best way to address that.

--
Robert Haas
EDB: http://www.enterprisedb.com