Re: Set visibility map bit after HOT prune

Pavan Deolasee <pavan.deolasee@gmail.com> writes:
> Ok. Will try to read archives to see what was actually suggested and
> why it was put on back burner. BTW at the risk of being shot down
> again, I wonder if can we push down the freeze operation to HOT prune
> also.

Seems unlikely to be a win.  We only care about freezing tuples in the
context of being able to advance a relation-wide relfrozenxid horizon.
Freezing pages retail accomplishes nothing whatsoever towards that goal,
unless you have some way to know that no new freeze work will be needed
on the page before the next vacuum freeze happens.  Otherwise, you're
just moving portions of the work from background vacuuming into
foreground processes, with no benefit gained thereby.  In fact, you
might well be *creating* work that would otherwise not have had to be
done at all --- the tuple might get deleted before the next freeze
happens.
        regards, tom lane