From: Tom Lane <tgl@sss.pgh.pa.us>
To: Michel Pelletier <pelletier.michel@gmail.com>
cc: pgsql-general <pgsql-general@lists.postgresql.org>
Subject: Re: Using Expanded Objects other than Arrays from plpgsql
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Comments: In-reply-to Michel Pelletier <pelletier.michel@gmail.com>
	message dated "Sun, 20 Oct 2024 11:25:30 -0700"
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Date: Sun, 20 Oct 2024 15:19:00 -0400
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Michel Pelletier <pelletier.michel@gmail.com> writes:
> On Sun, Oct 20, 2024 at 10:13 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> The other problem is that plpgsql only knows how to do such expansion
>> for arrays, and it's not obvious how to extend that part.

> Perhaps a third member function for ExpandedObjectMethods that formalizes
> the expansion interface like found in DatumGetExpandedArray?  I closely
> follow that same pattern in my code.

The trouble is we don't have an expanded object to consult at this
point --- only a flat Datum.  plpgsql has hard-wired knowledge that
it's okay to apply expand_array if the datatype passes the typisarray
tests, but I'm pretty unclear on how to provide similar knowledge for
extension datatypes.

			regards, tom lane