Re: What is "wraparound failure", really?

On Mon, Jun 28, 2021 at 08:51:50AM -0400, Andrew Dunstan wrote:
> On 6/28/21 2:39 AM, Peter Geoghegan wrote:
> > I agree that in practice that's often fine. But my point is that there
> > is another very good reason to not increase autovacuum_freeze_max_age,
> > contrary to what the docs say (actually there is a far better reason
> > than truncating clog). Namely, increasing it will generally increase
> > the risk of VACUUM not finishing in time.

Yep, that doc section's priorities are out of date.

> But if you're really worried about people setting
> autovacuum_freeze_max_age too high, then maybe we should be talking
> about capping it at a lower level rather than adjusting the docs that
> most users don't read.

If a GUC minimum or maximum feels like a mainstream choice, it's probably too
strict.  Hence, I think the current maximum is fine.  At 93% of the XID space,
it's not risk-averse, but it's not absurd.