From: Tom Lane <tgl@sss.pgh.pa.us>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: Make pg_interpret_timezone_abbrev() check sp->defaulttype too.
Date: Thu, 16 Jan 2025 17:43:13 +0000
Message-ID: <E1tYTtg-001x3U-UB@gemulon.postgresql.org> (raw)
Make pg_interpret_timezone_abbrev() check sp->defaulttype too.
This omission caused it to not recognize the furthest-back zone
abbreviation when working with timezone data compiled with relatively
recent zic (2018f or newer). Older versions of zic produced a dummy
DST transition at the Big Bang, so that the oldest abbreviation could
always be found in the sp->types[] array; but newer versions don't do
that, so that we must examine defaulttype as well as the types[] array
to be sure of seeing all the abbreviations.
While this has been broken for six or so years, we'd managed not
to notice for two reasons: (1) many platforms are still using
ancient zic for compatibility reasons, so that the issue did not
manifest in builds using --with-system-tzdata; (2) the oldest
zone abbreviation is almost always "LMT", which we weren't
supporting anyway (but an upcoming patch will accept that).
While at it, update pg_next_dst_boundary() to use sp->defaulttype
as the time type for non-DST zones and times before the oldest
DST transition. The existing code there predates upstream's
invention of the sp->defaulttype field, and its heuristic for
finding the oldest time type has now been subsumed into the
code that sets sp->defaulttype.
Possibly this should be back-patched, but I'm not currently aware
of any visible consequences of this bug in released branches.
Per report from Aleksander Alekseev and additional investigation.
Discussion: https://postgr.es/m/CAJ7c6TOATjJqvhnYsui0=CO5XFMF4dvTGH+skzB--jNhqSQu5g@mail.gmail.com
Branch
------
master
Details
-------
https://git.postgresql.org/pg/commitdiff/bc10219b9c8931ff4f872b3e799da2208101c574
Modified Files
--------------
src/timezone/localtime.c | 40 ++++++++++++++++++++--------------------
1 file changed, 20 insertions(+), 20 deletions(-)
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To: pgsql-committers@postgresql.org
Cc: tgl@sss.pgh.pa.us, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Make pg_interpret_timezone_abbrev() check sp->defaulttype too.
In-Reply-To: <E1tYTtg-001x3U-UB@gemulon.postgresql.org>
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