From: Tom Lane <tgl@sss.pgh.pa.us>
To: Dmitry Dolgov <9erthalion6@gmail.com>
cc: drewk@cockroachlabs.com, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #18463: Possible bug in stored procedures with polymorphic
 OUT parameters
In-reply-to: <20240515143506.pln5mzipy7iwa45i@ddolgov.remote.csb>
References: <18463-f8cd77e12564d8a2@postgresql.org>
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 <20240515143506.pln5mzipy7iwa45i@ddolgov.remote.csb>
Comments: In-reply-to Dmitry Dolgov <9erthalion6@gmail.com>
	message dated "Wed, 15 May 2024 16:35:06 +0200"
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Date: Wed, 15 May 2024 13:28:57 -0400
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Dmitry Dolgov <9erthalion6@gmail.com> writes:
> I'm now curious why it is different for functions, when creating one
> with an INOUT ANYELEMENT argument and record return type will error out.
> Disabling the corresponding ereport check in CreateFunction seems to
> produce a function that works in the similar way as the procedure in
> this thread. Are those type of functions incorrect in some way?

With procedures, there's no explicit RETURNS clause; we just
automatically fill RECORD into prorettype because (a) we gotta
put something and (b) that's the right thing anyway if there's
multiple OUT parameters.  Arguably it's not wrong for a single
output parameter, either, since CALL will return a tuple in
that case too.  I think it might've been better to put VOID
for the case of zero output parameters, since CALL doesn't
return a zero-column tuple in that case.  But that ship's
sailed, and it's not worth quibbling about.

We do this differently for functions: if there's exactly one
output parameter, that is the function result, so prorettype
has to match.  If we were to allow RETURNS RECORD with a
single output parameter, I think that'd have to mean that
we return a one-column tuple containing that parameter value.
That's not implemented, and I have doubts that it'd be useful.
It'd certainly be a bit inefficient.

			regards, tom lane