From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
cc: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>,
        PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: More tzdb fun: POSIXRULES is being deprecated upstream
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Comments: In-reply-to Robert Haas <robertmhaas@gmail.com>
	message dated "Fri, 19 Jun 2020 16:02:03 -0400"
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Date: Fri, 19 Jun 2020 16:22:04 -0400
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Robert Haas <robertmhaas@gmail.com> writes:
> On Fri, Jun 19, 2020 at 3:55 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> What I'm concerned about is that people depending on the existing
>> behavior are likely to wake up one fine morning and discover that it's
>> broken after a routine tzdata update.  I think that it'd be a better
>> user experience for them to see a release-note entry in a PG update
>> release explaining that this will break and here's what to do to fix it.

> I was assuming that if you did an update of the tzdata, you'd notice
> if posixrules had been nuked. I guess that wouldn't help people who
> are using the system tzdata, though.

Yeah, exactly.  We can control this easily enough for PG-supplied tzdata
trees, but I think a significant majority of actual users are using
--with-system-tzdata builds, because we've been telling packagers to
do it that way for years.  (Nor does changing that advice seem like
a smart move.)

> It might be nice to know what
> Debian, RHEL, etc. plan to do about this, but I'm not sure how
> practical it is to find out.

There's probably no way to know until it happens :-(.  We can hope
that they'll be conservative, but it's hard to be sure.  It doesn't
help that the bigger players rely on glibc: if I understand what
Eggert was saying, nuking posixrules would bring tzcode's behavior
into closer sync with what glibc does, so they might well feel it's
a desirable change.

			regards, tom lane