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: Andrew Gierth <andrew@tao11.riddles.org.uk>
Cc: Thomas Munro <thomas.munro@gmail.com>, 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: 2019-06-26T17:06:55Z
Lists: pgsql-hackers 
Andrew Gierth <andrew@tao11.riddles.org.uk> writes:
> "Thomas" == Thomas Munro <thomas.munro@gmail.com> writes:
>  Thomas> Right. On a FreeBSD system here in New Zealand you get "NZ"
>  Thomas> with default configure options (ie using PostgreSQL's tzdata).
>  Thomas> But if you build with --with-system-tzdata=/usr/share/zoneinfo
>  Thomas> you get "Pacific/Auckland", and that's because the FreeBSD
>  Thomas> zoneinfo directory doesn't include the old non-city names like
>  Thomas> "NZ", "GB", "Japan", "US/Eastern" etc.

> Same issue here with Europe/London getting "GB".

FreeBSD offers yet another obstacle to Andrew's proposal:

$ uname -a
FreeBSD rpi3.sss.pgh.pa.us 12.0-RELEASE FreeBSD 12.0-RELEASE r341666 GENERIC  arm64
$ ls /usr/share/zoneinfo/
Africa/         Australia/      Etc/            MST             WET
America/        CET             Europe/         MST7MDT         posixrules
Antarctica/     CST6CDT         Factory         PST8PDT         zone.tab
Arctic/         EET             HST             Pacific/
Asia/           EST             Indian/         SystemV/
Atlantic/       EST5EDT         MET             UTC

No zone1970.tab.  I do not think we can rely on that file being there,
since zic itself doesn't install it; it's up to packagers whether or
where to install the "*.tab" files.

In general, the point I'm trying to make is that our policy should be
"Ties are broken arbitrarily, and if you don't like the choice that initdb
makes, here's how to fix it".  As soon as we try to break some ties in
favor of somebody's idea of what is "right", we are in for neverending
problems with different people disagreeing about what is "right", and
insisting that their preference should be the one the code enforces.
Let's *please* not go there, or even within hailing distance of it.

(By this light, even preferring UTC over UCT is a dangerous precedent.
I won't argue for reverting that, but I don't want to go further.)

			regards, tom lane

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.