Re: Collation version tracking for macOS

On Fri, Jun 10, 2022 at 1:06 PM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
> On Thu, Jun 9, 2022 at 5:59 PM Thomas Munro <thomas(dot)munro(at)gmail(dot)com> wrote:
> > That sounds nice, but introduces subtle problems for the planner. For
> > example, pathkeys that look compatible might not be, when
> > merge-joining an ICU 63 index scan against an ICU 67 index scan. You
> > could teach it about that, whereas with my distinct OID concept they
> > would already be considered non-matching automatically.
>
> Right -- my proposal is likely to be more difficult to implement.
> Seems like it might be worth going to the trouble of teaching the
> planner about this difference, though.

Well I can report that the system from ec483147 was hellishly
complicated, and not universally loved. Which isn't to say that there
isn't a simple and loveable way to do it, waiting to be discovered,
and I do think we could fix most of the problems with that work. It's
just that I was rather thinking of this new line of attack as being a
way to avoid the complications of identifying dependencies on moving
things through complicated analysis of object graphs and AST, by
instead attaching those slippery external things to the floor with a
nail gun. That is, treating ICU 63 and ICU 67's collations as
completely unrelated. I understand that that's not ideal from an
end-user perspective, but maybe it's more realistically and robustly
and simply implementable. Hmm.