From: Tom Lane <tgl@sss.pgh.pa.us>
To: Chapman Flack <jcflack@acm.org>
cc: PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Subject: Re: FmgrInfo allocation patterns (and PL handling as staged
 programming)
In-reply-to: <67F40ACD.7040507@acm.org>
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 <2968353.1743962392@sss.pgh.pa.us> <67F40ACD.7040507@acm.org>
Comments: In-reply-to Chapman Flack <jcflack@acm.org>
	message dated "Mon, 07 Apr 2025 13:26:37 -0400"
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Date: Mon, 07 Apr 2025 13:34:49 -0400
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Chapman Flack <jcflack@acm.org> writes:
> This was really bumming me out. I thought "what on earth does that do
> to the rest of your surrounding query, say if you have anyelement types
> in the args or return value also?".

> So the answer to that part is easy: if a routine's types include both
> anyarray and anyelement (like, say, unnest), it just can't be applied
> to one of those statistics columns. An attempt to use it that way in
> a query is rejected early, before any attempt to call the routine:

> ERROR:  cannot determine element type of "anyarray" argument
> STATEMENT:  select unnest(stavalues1) from pg_statistic limit 1;

Right.  AFAIK the oddity doesn't "leak out" of functions taking
anyarray.

> That seems to make for a tidy way of recognizing the situation. If
> you go to specialize and find anyarray among your supposedly-resolved
> call-site types, well, you know you're in Wonderland and can adjust
> behavior accordingly.

Cool.

			regards, tom lane