Re: Decoupling antiwraparound autovacuum from special rules around auto cancellation

On Mon, 2022-10-24 at 07:25 -0700, Peter Geoghegan wrote:
> The really important thing is giving a regular/early autocancellable
> autovacuum triggered by age(relfrozenxid) *some* opportunity to run.

+1. That principle seems both reasonable from a system standpoint and
understandable to a user.

> Even if regular/early autovacuum had just one
> opportunity to run to completion, we'd already be much better off.

By "opportunity", you mean that, regardless of configuration, the
cancellable autovacuum would at least start; though it still might be
cancelled by DDL. Right?

> These are all fundamentally the same operations with the
> same urgency to users, though. We'd only need to describe the
> *criteria* that *triggered* the autovacuum in our autovacuum log
> report

Hmm... I'm worried that could be a bit confusing depending on how it's
done. Let's be clear that it was merely the triggering criteria and
doesn't necessarily represent the work that is being done.

There are enough cases that it would be good to start a document and
outline the end behavior that your patch series is designed to
accomplish. In other words, a before/after of the interesting cases.


-- 
Jeff Davis
PostgreSQL Contributor Team - AWS