Re: Should we remove vacuum_defer_cleanup_age?

On Thu, Apr 13, 2023 at 11:06 PM Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> wrote:
> I am not against this in principle, but I know that there are people using
> this parameter; see the discussion linked in
>
> https://postgr.es/m/E1jkzxE-0006Dw-Dg@gemulon.postgresql.org
>
> I can't say if they have a good use case for that parameter or not.

Yeah, I feel similarly. Actually, personally I have no evidence, not
even an anecdote, suggesting that this parameter is in use, but I'm a
bit skeptical of any consensus of the form "no one is using X,"
because there sure are a lot of people running PostgreSQL and they
sure do a lot of things. Some more justifiably than others, but often
people have surprisingly good excuses for doing stuff that sounds
bizarre when you first hear about it, and it doesn't seem totally
impossible that somebody could have found a way to get value out of
this.

However, I suspect that there aren't many such people, and I think the
setting is a kludge, so I support removing it. Maybe we'll find out
that we ought to add something else instead, like a limited delimited
in time rather than in XIDs. Or maybe the existing facilities are good
enough. But as Peter rightly says, XID age is likely a poor proxy for
whatever people really care about, so I don't think continuing to have
a setting that works like that is a good plan.

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