Horton

Re: UCT (Re: pgsql: Update time zone data files to tzdata release 2019a.)

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Thomas Munro <thomas.munro@gmail.com>
Cc: Andrew Gierth <andrew@tao11.riddles.org.uk>, Robert Haas <robertmhaas@gmail.com>, Stephen Frost <sfrost@snowman.net>, Andres Freund <andres@anarazel.de>, Christoph Berg <myon@debian.org>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2019-07-25T20:35:15Z
Lists: pgsql-hackers

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Thomas Munro <thomas.munro@gmail.com> writes:
> FWIW this is now fixed for FreeBSD 13-CURRENT, with a good chance of
> back-patch.  I don't know if there are any other operating systems
> that are shipping zoneinfo but failing to install zone1970.tab, but if
> there are it's a mistake IMHO and they'll probably fix that if someone
> complains, considering that zone.tab literally tells you to go and use
> the newer version, and Paul Eggert has implied that zone1970.tab is
> the "full" and "canonical" list[1].

I'm not sure we're any closer to a meeting of the minds on whether
consulting zone[1970].tab is a good thing to do, but we got an actual
user complaint[1] about how "localtime" should not be a preferred
spelling.  So I want to go ahead and insert the discussed anti-preference
against "localtime" and "posixrules", as per 0001 below.  If we do do
something with zone[1970].tab, we'd still need these special rules,
so I don't think this is blocking anything.

Also, I poked into the question of the "Factory" zone a bit more,
and was disappointed to find that not only does FreeBSD still install
the "Factory" zone, but they are apparently hacking the data so that
it emits the two-changes-back abbreviation "Local time zone must be
set--use tzsetup".  This bypasses the filter in pg_timezone_names that
is expressly trying to prevent showing such silly "abbreviations".
So I now feel that not only can we not remove initdb's discrimination
against "Factory", but we indeed need to make the pg_timezone_names
filter more aggressive.  Hence, I now propose 0002 below to tweak
what we're doing with "Factory".  I did remove our special cases for
it in zic.c, as we don't need them anymore with modern tzdb data, and
there's no reason to support running "zic -P" with hacked-up data.

			regards, tom lane

[1] https://www.postgresql.org/message-id/CADT4RqCCnj6FKLisvT8tTPfTP4azPhhDFJqDF1JfBbOH5w4oyQ@mail.gmail.com

Commits

  1. Tweak our special-case logic for the IANA "Factory" timezone.

  2. Avoid choosing "localtime" or "posixrules" as TimeZone during initdb.

  3. Prefer timezone name "UTC" over alternative spellings.

  4. Attempt to identify system timezone by reading /etc/localtime symlink.

  5. Update time zone data files to tzdata release 2019a.