Re: Decoupling antiwraparound autovacuum from special rules around auto cancellation

On Fri, Jan 20, 2023 at 4:24 PM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
> > It sounds like they used DROP TRIGGER pretty regularly. So I think this
> > sounds like exactly the kind of case I was talking about, where
> > autovacuums keep getting cancelled until we decide to stop cancelling
> > them.
>
> I don't know how you can reach that conclusion.

I can accept that there might be some way I'm wrong about this in
theory, but your email then seems to go on to say that I'm right just
a few sentences later:

> The whole article was about how this DROP TRIGGER pattern worked just
> fine most of the time, because most of the time autovacuum was just
> autocancelled. They say this at one point:
>
> "The normal autovacuum mechanism is skipped when locks are held in
> order to minimize service disruption. However, because transaction
> wraparound is such a severe problem, if the system gets too close to
> wraparound, an autovacuum is launched that does not back off under
> lock contention."

If this isn't arguing in favor of exactly what I'm saying, I don't
know what that would look like.

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