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: Stephen Frost <sfrost@snowman.net>, Robert Haas <robertmhaas@gmail.com>, Alvaro Herrera <alvherre@2ndquadrant.com>, Andres Freund <andres@anarazel.de>, Christoph Berg <myon@debian.org>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2019-06-20T21:59:56Z
Lists: pgsql-hackers 
Andrew Gierth <andrew@tao11.riddles.org.uk> writes:
> Tom's "fix" of backpatching 23bd3cec6 (which happened on Friday 14th)
> addressed only a subset of cases, as far as I know working only on Linux
> (the historical convention has always been for /etc/localtime to be a
> copy of a zonefile, not a symlink to one). I only decided to write (and
> if need be commit) my own followup fix after confirming that the bug was
> unfixed in a default FreeBSD install when set to UTC, and there was a
> good chance that a number of other less-popular platforms were affected
> too.

I think your info is out of date on that.

NetBSD uses a symlink, and has done for at least 5 years: see
set_timezone in
http://cvsweb.netbsd.org/bsdweb.cgi/src/usr.sbin/sysinst/util.c?only_with_tag=MAIN

macOS seems to have done it like that for at least 10 years, too.
I didn't bother digging into their source repo, as it's likely that
System Preferences isn't open-source; but *all* of my macOS machines
have symlinks there, and some of those link files are > 10 years old.

I could not easily find OpenBSD's logic to set the zone during install,
if they have any; but at least their admin-facing documentation says to
create the file as a symlink:
https://www.openbsd.org/faq/faq8.html#TimeZone
and there are plenty of similar recommendations found by Mr. Google.

In short, I think FreeBSD are holdouts not the norm.  I note that
even their code will preserve /etc/localtime's symlink status if
it was a symlink to start with: see install_zoneinfo_file in
https://github.com/freebsd/freebsd/blob/master/usr.sbin/tzsetup/tzsetup.c

			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.