From: Tom Lane <tgl@sss.pgh.pa.us>
To: "Voillequin, Jean-Marc" <Jean-Marc.Voillequin@moodys.com>
cc: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>,
        pgsql-bugs@lists.postgresql.org, pgsql-sql@lists.postgresql.org
Subject: Re: Weird "could not determine which collation to use for string
 comparison" with LEAST/GREATEST on PG11 procedure
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Comments: In-reply-to "Voillequin,
 Jean-Marc" <Jean-Marc.Voillequin@moodys.com>
	message dated "Wed, 21 Nov 2018 14:09:55 +0000"
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Date: Wed, 21 Nov 2018 13:19:20 -0500
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"Voillequin, Jean-Marc" <Jean-Marc.Voillequin@moodys.com> writes:
> SIMPLE=3D> create or replace procedure same_values_proc(a text, b text) =
as $body$
> SIMPLE$> begin
> SIMPLE$>        assert a =3D b;
> SIMPLE$> end;$body$ language plpgsql;
> CREATE PROCEDURE
> SIMPLE=3D>
> SIMPLE=3D> call same_values_proc(least('a','b'),'a');
> ERROR:  could not determine which collation to use for string comparison
> HINT:  Use the COLLATE clause to set the collation explicitly.

Yeah, same here.  I think somebody forgot to run assign_expr_collations()
on CALL arguments.

			regards, tom lane