From: Tom Lane <tgl@sss.pgh.pa.us>
To: Thomas Munro <thomas.munro@gmail.com>
Cc: Michael Paquier <michael@paquier.xyz>
Cc: Vik Fearing <vik@postgresfriends.org>
Cc: cary huang <hcary328@gmail.com>
Cc: pgsql-hackers@lists.postgresql.org
Subject: Re: Add support for AT LOCAL
Date: Sun, 15 Oct 2023 17:57:51 -0400
Message-ID: <2129576.1697407071@sss.pgh.pa.us> (raw)
In-Reply-To: <CA+hUKGK=DOC+hE-62FKfZy=Ybt5uLkrg3zCZD-jFykM-iPn8yw@mail.gmail.com>
References: <169541920143.2315938.17412414971559687288.pgcf@coridan.postgresql.org>
<dbea9877-f39b-1a5b-6e5b-5aad2bbc2821@postgresfriends.org>
<ZRZ8ePmlhx_1LvVV@paquier.xyz>
<c2c6f2c3-49e3-c1fe-65ca-49f275af41c2@postgresfriends.org>
<ZR-jmKYU5BDQEAe4@paquier.xyz>
<e3b4c42d-739d-4375-9401-2f62ad59d326@postgresfriends.org>
<ZSTUWON7DOfo-2ES@paquier.xyz>
<a2bd6444-7fe4-44cd-8cb6-d7ac13f4d3e0@postgresfriends.org>
<ZSjCZJrxGL0-wv-G@paquier.xyz>
<65b620bd-4f05-4381-97c3-5ec9ac39d5b9@postgresfriends.org>
<ZSjQj34RZBY_HY0c@paquier.xyz>
<CA+hUKGK=DOC+hE-62FKfZy=Ybt5uLkrg3zCZD-jFykM-iPn8yw@mail.gmail.com>
Thomas Munro <thomas.munro@gmail.com> writes:
> One of the AIX animals gave a strange result here:
> https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=hornet&dt=2023-10-15%2011%3A40%3A01> If you ignore the diffs due to change in column width, the interesting
> change seems to be:
> - 23:59:00-07 | 06:59:00+00 | 06:59:00+00 | 06:59:00+00
> - 23:59:59.99-07 | 06:59:59.99+00 | 06:59:59.99+00 | 06:59:59.99+00
> + 23:59:00-07 | 4294966103:4294967295:00+00 |
> 4294966103:4294967295:00+00 | 4294966103:4294967295:00+00
> + 23:59:59.99-07 | 4294966103:00:00.01+00 |
> 4294966103:00:00.01+00 | 4294966103:00:00.01+00
> But the other AIX animal 'sungazer' was OK with it. They're both on
> the same AIX7.1 host IIRC, both 64 bit builds, but the former is using
> xlc and the latter gcc. I don't immediately see what would cause that
> underflow on that old compiler but not elsewhere. I have a shell
> there (cfarm111) if someone has an idea...
Hmm. Seems like the error has to be creeping in during this part
of timetz_zone():
result->time = t->time + (t->zone - tz) * USECS_PER_SEC;
while (result->time < INT64CONST(0))
result->time += USECS_PER_DAY;
while (result->time >= USECS_PER_DAY)
result->time -= USECS_PER_DAY;
According to my machine, the initial computation of result->time
(for the '23:59:59.99-07' input) yields 111599990000, and then we
iterate the second loop once to get 25199990000, which is the right
answer. If I force a second iteration to get -61200010000, I get
# select '23:59:59.99-07'::timetz at local;
timezone
------------------------
4294967279:00:00.01+00
(1 row)
which doesn't quite match hornet's result but it seems
suggestively close.
Another line of thought is that while the time fields are int64,
t->zone and tz are only int32. Multiplying by the INT64CONST
USECS_PER_SEC ought to be enough to make the compiler widen
the subtraction result to int64, but maybe that's screwing up?
I'm tempted to wonder if this helps:
- result->time = t->time + (t->zone - tz) * USECS_PER_SEC;
+ result->time = t->time + (int64) (t->zone - tz) * USECS_PER_SEC;
Forcing the wrong thing to happen there doesn't produce a match
to hornet's result either, so I don't have a lot of hope for that
theory, but it seems like the explanation has to be somewhere here.
regards, tom lane
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To: pgsql-hackers@postgresql.org
Cc: tgl@sss.pgh.pa.us, thomas.munro@gmail.com, michael@paquier.xyz, vik@postgresfriends.org, hcary328@gmail.com, pgsql-hackers@lists.postgresql.org
Subject: Re: Add support for AT LOCAL
In-Reply-To: <2129576.1697407071@sss.pgh.pa.us>
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