Re: Adding REPACK [concurrently]

Hi,

So here's a v55 version of the base REPACK patches that I'm feeling
comfortable calling very close to committable. I'm going to give an
additional read tomorrow and maybe make cosmetic adjustments, but there
should be nothing substantial. Of course, the subsequent additions in
the other patches of v54 are still in the cards, and they are most
likely essential.

Changes compared to v54:
- changed reform_tuple() to not deform the tuple if no attributes are
going to be touched. We can simply make a copy instead, which I
suspect is considerably cheaper (but I didn't measure).

- cleaned up worker shmem shutdown callback. I think it's how it is
because it copied parallel worker code, but that has a weird structure
for --as far as I can see-- no good reason (we oughta change it too)

- renamed the worker from pgoutput_repack to pgrepack.
(Note that this is an internal name that users don't face.)

- reverted some unnecessary changes to master

Thanks

--
Álvaro Herrera 48°01'N 7°57'E — https://www.EnterpriseDB.com/