Re: Emit fewer vacuum records by reaping removable tuples during pruning

On Wed, Dec 27, 2023 at 11:27 AM Melanie Plageman
<melanieplageman(at)gmail(dot)com> wrote:
> Do you have specific concerns about its correctness? I understand it
> is an area where we have to be sure we are correct. But, to be fair,
> that is true of all the pruning and vacuuming code.

I'm kind of concerned that 0002 might be a performance regression. It
pushes more branches down into the heap-pruning code, which I think
can sometimes be quite hot, for the sake of a case that rarely occurs
in practice. I take your point about it improving things when there
are no indexes, but what about when there are? And even if there are
no adverse performance consequences, is it really worth complicating
the logic at such a low level?

Also, I find "pronto_reap" to be a poor choice of name. "pronto" is an
informal word that seems to have no advantage over something like
"immediate" or "now," and I don't think "reap" has a precise,
universally-understood meaning. You could call this "mark_unused_now"
or "immediately_mark_unused" or something and it would be far more
self-documenting, IMHO.

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