Re: BUG #19816: PL/Python SD dictionary is split by input collation in 19rc1

I wrote:
> So I'm now coming around to the conclusion that bug compatibility
> with the old behavior is the way to go. Maybe we will rethink
> that when/if we get around to supporting polymorphic arguments,
> but we don't have to make a decision about that today. If we
> split off a separate hashtable as Shihao's v1 patch does, then
> we've successfully decoupled the SD behavior from funccache.c's
> rules, and we will be free to go either way when the time comes.

> So I think Shihao's patch is the right thing (at least approximately,
> I haven't read it in detail), and I'll move forward with that.

Okay, so I started looking at the patch and immediately realized
that it's set up to replace SD any time the function is redefined.
I think that's taking bug-compatibility with the old behavior a
bit too far: you certainly would not get that impression from
the manual's description. I propose we drop that behavior and
just run with the function OID and trigger relation as hash keys.

As a minor criticism, I find it odd to make PLy_procedure_compile
sometimes create the SD dictionary and sometimes not. There are
only two callers, so I'm more inclined to require both callers
to handle that.

regards, tom lane