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

>>>>> "Christoph" == Christoph Berg <myon(at)debian(dot)org> writes:

>> Etc/UCT is now a backward-compatibility link to Etc/UTC, instead of
>> being a separate zone that generates the abbreviation "UCT", which
>> nowadays is typically a typo. Postgres will still accept "UCT" as an
>> input zone name, but it won't output it.

Christoph> There is something wrong here. On Debian Buster/unstable,
Christoph> using system tzdata (2019a-1), if /etc/timezone is
Christoph> "Etc/UTC":

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

Christoph> Is that expected behavior?

It's clearly not what users expect and it's clearly the wrong thing to
do, though it's the expected behavior of the current code:

* On most systems, we rely on trying to match the observable behavior of
* the C library's localtime() function. The database zone that matches
* furthest into the past is the one to use. 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.

I believe I pointed out a long, long time ago that this tie-breaking
strategy was insane, and that the rule should be to prefer canonical
names and use something else only in the case of a strictly better
match.

If TZ is set or if /etc/localtime is a symlink rather than a hardlink or
copy of the zone file, then PG can get the zone name directly rather
than having to do the comparisons, so the above comment doesn't apply;
that gives you a workaround.

--
Andrew (irc:RhodiumToad)