From: Tom Lane <tgl@sss.pgh.pa.us>
To: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
cc: Thomas Munro <thomas.munro@gmail.com>,
        Petr Fedorov <petr.fedorov@phystech.edu>,
        pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: Since '2001-09-09 01:46:40'::timestamp microseconds are lost when
 extracting epoch
In-reply-to: <ee683994-8f7c-aded-be43-543e66e68b94@2ndquadrant.com>
References: <42b73d2d-da12-ba9f-570a-420e0cce19d9@phystech.edu>
 <CA+hUKGKgHUbFNKRhvodn4mVU-oqje+HA7jTg_XrWRo4UGhFoqg@mail.gmail.com>
 <18389.1575241151@sss.pgh.pa.us>
 <1c2262e2-6812-7baa-cbdd-63039db12952@phystech.edu>
 <CA+hUKGK+K8NyS57tU841m1tSF6ha3W0udN2dw_Hbc=D_0OPbmA@mail.gmail.com>
 <ee683994-8f7c-aded-be43-543e66e68b94@2ndquadrant.com>
Comments: In-reply-to Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
	message dated "Mon, 25 May 2020 15:28:54 +0200"
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <27489.1590414212.1@sss.pgh.pa.us>
Date: Mon, 25 May 2020 09:43:32 -0400
Message-ID: <27490.1590414212@sss.pgh.pa.us>
Precedence: bulk

Peter Eisentraut <peter.eisentraut@2ndquadrant.com> writes:
> One problem (other than perhaps performance, tbd.) is that this would no 
> longer allow processing infinite timestamps, since numeric does not 
> support infinity.  It could be argued that running extract() on infinite 
> timestamps isn't very useful, but it's something to consider explicitly.

I wonder if it's time to fix that, ie introduce +-Infinity into numeric.c.
This isn't the first time we've seen issues with numeric not being a
superset of float, and it won't be the last.

At first glance there's no free bits in the on-disk format for numeric,
but we could do something by defining the low-order bits of the header
word for a NaN to distinguish between real NaN and +/- infinity.
It looks like those bits should reliably be zero right now.

			regards, tom lane