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: Christoph Berg <myon@debian.org>
Cc: PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2019-06-04T15:27:31Z
Lists: pgsql-hackers 
Christoph Berg <myon@debian.org> writes:
> There is something wrong here. On Debian Buster/unstable, using
> system tzdata (2019a-1), if /etc/timezone is "Etc/UTC":

> 11.3's initdb adds timezone = 'UCT' to postgresql.conf
> 12beta1's initdb add timezone = 'Etc/UCT' to postgresql.conf

Hm, I don't have a Debian machine at hand, but I'm unable to
reproduce this using macOS or RHEL.  I tried things like

$ TZ=UTC initdb
...
selecting default timezone ... UTC
...

Is your build using --with-system-tzdata?  If so, which tzdb
release is the system on, and is it a completely stock copy
of that release?

Given the tie-breaking behavior in findtimezone.c,

 * ... Often there will be several
 * zones with identical rankings (since the IANA database assigns multiple
 * names to many zones).  We break ties arbitrarily by preferring shorter,
 * then alphabetically earlier zone names.

it's not so surprising that UCT might be chosen, but I don't
understand how Etc/UCT would be.

BTW, does Debian set up /etc/timezone as a symlink, by any chance,
rather than a copy or hard link?  If it's a symlink, we could improve
matters by teaching identify_system_timezone() to inspect it.

			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.