Re: Decoupling antiwraparound autovacuum from special rules around auto cancellation

On Thu, Oct 20, 2022 at 11:52 AM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
> Leaving my patch series aside, I still don't think that it makes sense
> to make it impossible to auto-cancel antiwraparound autovacuums,
> across the board, regardless of the underlying table age.

One small thought on the presentation/docs side of this: maybe it
would be better to invent a new kind of autovacuum that has the same
purpose as antiwraparound autovacuum, but goes by a different name,
and doesn't have the special behavior around cancellations. We
wouldn't have to change anything about the behavior of antiwraparound
autovacuum once we reached the point of needing one.

Maybe we wouldn't even need to invent a new user-visible name for this
other kind of autovacuum. While even this so-called "new kind of
autovacuum" will be rare once my main patch series gets in, it'll
still be a totally normal occurrence. Whereas antiwraparound
autovacuums are sometimes described as an emergency mechanism.

That way we wouldn't be fighting against the widely held perception
that antiwraparound autovacuums are scary. In fact that reputation
would be fully deserved, for the first time. There are lots of
problems with the idea that antiwraparound autovacuum is kind of an
emergency thing right now, but this would make things fit the
perception, "fixing" the perception. Antiwraparound autovacuums would
become far far rarer under this scheme, but when they did happen
they'd be clear cause for concern. A useful signal for users, who
should ideally aim to never see *any* antiwraparound autovacuums.

--
Peter Geoghegan