From: Tom Lane <tgl@sss.pgh.pa.us>
To: Braiam <braiamp@gmail.com>
cc: braiamp+pg@gmail.com, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #18007: age(timestamp, timestamp) is marked as immutable,
 but using age(date, date) says it's not
In-reply-to: 
 <CAG=7Bt_DtoMoAA7iKCgYvV2Np1Xv1K29QKGggihnt04WSrAKfQ@mail.gmail.com>
References: <18007-036782307e002bf6@postgresql.org>
 <1573129.1688061162@sss.pgh.pa.us>
 <CAG=7Bt_DtoMoAA7iKCgYvV2Np1Xv1K29QKGggihnt04WSrAKfQ@mail.gmail.com>
Comments: In-reply-to Braiam <braiamp@gmail.com>
	message dated "Thu, 29 Jun 2023 14:20:44 -0400"
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Date: Thu, 29 Jun 2023 14:24:47 -0400
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Braiam <braiamp@gmail.com> writes:
> On Thu, Jun 29, 2023 at 1:52=E2=80=AFPM Tom Lane <tgl@sss.pgh.pa.us> wro=
te:
>> There is no age(date, date) function.  What we have is age(timestamp,
>> timestamp) and age(timestamptz, timestamptz), so the parser has to
>> choose which type to coerce to --- and it prefers timestamptz.

> According to \df+ age both timestamptz and timestamp are immutable:

True, but not very relevant: it's the coercion from date that's
giving you trouble.

> So, whatever type is coerced into pre-function evaluation comes
> with strange results. I'm not aware of a way that I can see what
> kind of type is being coerced into.

EXPLAIN will show that, eg

=3D# explain verbose select age(current_date, current_date);
                                            QUERY PLAN                    =
      =

                   =

--------------------------------------------------------------------------=
-------------------------
 Result  (cost=3D0.00..0.02 rows=3D1 width=3D16)
   Output: age((CURRENT_DATE)::timestamp with time zone, (CURRENT_DATE)::t=
imestamp with time zone)
(2 rows)

			regards, tom lane