From: Tom Lane <tgl@sss.pgh.pa.us>
To: Thomas Munro <thomas.munro@gmail.com>
cc: Petr Fedorov <petr.fedorov@phystech.edu>, pgsql-bugs@postgresql.org
Subject: Re: Since '2001-09-09 01:46:40'::timestamp microseconds are lost when
 extracting epoch
In-reply-to: 
 <CA+hUKGKgHUbFNKRhvodn4mVU-oqje+HA7jTg_XrWRo4UGhFoqg@mail.gmail.com>
References: <42b73d2d-da12-ba9f-570a-420e0cce19d9@phystech.edu>
 <CA+hUKGKgHUbFNKRhvodn4mVU-oqje+HA7jTg_XrWRo4UGhFoqg@mail.gmail.com>
Comments: In-reply-to Thomas Munro <thomas.munro@gmail.com>
	message dated "Mon, 02 Dec 2019 11:50:00 +1300"
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <18388.1575241151.1@sss.pgh.pa.us>
Content-Transfer-Encoding: quoted-printable
Date: Sun, 01 Dec 2019 17:59:11 -0500
Message-ID: <18389.1575241151@sss.pgh.pa.us>
Precedence: bulk

Thomas Munro <thomas.munro@gmail.com> writes:
> On Sat, Nov 30, 2019 at 10:28 PM Petr Fedorov <petr.fedorov@phystech.edu=
> wrote:
>> Obviously, it is due to the fact that extract epoch returns double
>> precision which in turn has 15 decimal digits precision.

> I guess this deviation from the SQL standard ("exact numeric") made
> sense when PostgreSQL used double for timestamps, but would break a
> lot of queries if we changed it.

Hmmm ... well, now that you mention it, would it really break things
if we made it return numeric?  There's an implicit cast to float8,
so it seems like queries requiring that type would still work.

There might be a performance-related argument against switching,
perhaps.

			regards, tom lane