Michael Paquier <michael(dot)paquier(at)gmail(dot)com> writes:
> In short, autovacuum will need to scan by itself the VM of each
> relation and decide based on that.
That seems like a worthwhile approach to pursue. The VM is supposed to be
small, and if you're worried it isn't, you could sample a few pages of it.
I do not think any of the ideas proposed so far for tracking the
visibility percentage on-the-fly are very tenable.
regards, tom lane