Re: Emit fewer vacuum records by reaping removable tuples during pruning - Mailing list pgsql-hackers

On Fri, Jan 12, 2024 at 1:52 PM Melanie Plageman
<melanieplageman@gmail.com> wrote:
> On Fri, Jan 12, 2024 at 1:07 PM Peter Geoghegan <pg@bowt.ie> wrote:
> > What is "space_freed"? Isn't that something from your uncommitted patch?
>
> Yes, I was mixing the two together.

An understandable mistake.

> I just want to make sure that we agree that, on master, when
> lazy_scan_prune() is called, the logic for whether or not to update
> the FSM after the first pass is:
>
> indexes == 0 || !has_lpdead_items || !index_vacuuming
>
> and when lazy_scan_noprune() is called, the logic for whether or not
> to update the FSM after the first pass is:
>
> indexes == 0 || !has_lpdead_items
>
> Those seem different to me.

Right. As I said to Robert just now, I can now see that they're
slightly different conditions.

FWIW my brain was just ignoring " || !index_vacuuming". I dismissed it
as an edge-case, only relevant when the failsafe has kicked in. Which
it is. But that's still no reason to allow an inconsistency that we
can easily just avoid.

--
Peter Geoghegan