Remove AIX Support (was: Re: Relation bulk write facility)

Hi,

On Sat, Feb 24, 2024 at 01:29:36PM -0800, Andres Freund wrote:
> Let's just drop AIX. This isn't the only alignment issue we've found and the
> solution for those isn't so much a fix as forcing everyone to carefully only
> look into one direction and not notice the cliffs to either side.

While I am not against dropping AIX (and certainly won't step up to
maintain it just for fun), I don't think burying this inside some
"Relation bulk write facility" thread is helpful; I have changed the
thread title as a first step.

The commit message says there is not a lot of user demand and that might
be right, but contrary to other fringe OSes that got removed like HPPA
or Irix, I believe Postgres on AIX is still used in production and if
so, probably in a mission-critical manner at some old-school
institutions (in fact, one of our customers does just that) and not as a
thought-experiment. It is probably well-known among Postgres hackers
that AIX support is problematic/a burden, but the current users might
not be aware of this.

Not sure what to do about this (especially now that this has been
committed), maybe there should have been be a public deprecation notice
first for v17... On the other hand, that might not work if important
features like direct-IO would have to be bumped from v17 just because of
AIX.

I posted about this on Twitter and Mastodon to see whether anybody
complains and did not get a lot of feedback.

In any case, users will have a couple of years to migrate as usual if
they upgrade to v16.

Michael