Hi Pavel,
I've looked into your patch and provide the review below.
Threads I found touching TMMONTH + glibc:
https://www.postgresql.org/message-id/CALSKcLS3Zi4o0Ak5pNOheqmAiKWcez%2B%2BqwKvyPccvOz2v62QZQ%40mail.gmail.com
(Russian)
https://www.postgresql.org/message-id/14717914.JAiOoc7IO7%40utklippan
I did not come across a prior thread proposing an implementation of what
this patch does. Worth noting that in the utklippan thread above, Tom Lane
suggested that a new format code or modifier would be the palatable way to
address a similar problem.
Contents & Purpose
==================
This patch gives users control over the case (genitive vs. nominative)
to use when pulling localized month names from glibc via the function
to_char(). The author proposes to add a TAMMONTH option for formatting
dates.
Intended behaviour: TMMONTH uses the genitive form (if applicable to the
language; equivalent to %B) while TAMMONTH uses the nominative
(equivalent to %OB).
The patch contains regression test cases. It also adds a corresponding
entry in the documentation.
Initial Run
===========
The patch applies cleanly to HEAD. The regression tests all pass
successfully against the new patch, but fail against pre-patched HEAD,
so the test cases are sane and do cover the new behavior.
Manual Testing
==============
The provided examples all work fine. However, I realized that the
shortened form TAMMON falls back to English instead of honouring
lc_time:
postgres=# set lc_time to 'de_DE.UTF-8';
SET
postgres=# SELECT to_char(date '2026-03-01'::date, 'DD TMMON');
SELECT to_char(date '2026-03-01'::date, 'DD TAMMON');
to_char
---------
01 MÄR
(1 row)
to_char
---------
01 MAR
(1 row)
It looks like only the full-month cases (DCH_MONTH/Month/month) were
wired up for
TAM; the abbreviated cases (DCH_MON/Mon/mon) still test IS_SUFFIX_TM
only, so TAM
silently drops to the default English abbreviation. I'd expect TAMMON to
stay
localized.
Code Review
===========
I am not sure if this condition can be ever true:
+ if (IS_SUFFIX_TM(n->suffix) && IS_SUFFIX_TAM(n->suffix))
In case this is not possible the subsequent error message will never be
thrown and the whole block is dead code.
However, if there is a reason for this check, it would be nice to
have a comment mention it.
One thing I am not entirely sure about is this line:
+ if (strftime_l(bufptr, MAX_L10N_DATA, "%OB", timeinfo, locale) <= 0)
+ strftimefail = true;
As far as I checked %OB is not supported on Windows:
https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/strftime-wcsftime-strftime-l-wcsftime-l?view=msvc-170
I was, however, not able to confirm this on a Windows machine right now.
I might be able to do so on the weekend.
However, the same problem exists with older glibc versions not supporting
%OB. As far as I understand strftime_l this will lead to it returning 0 and
therefore setting strftimefail to true always. Since this if statement
is evaluated
unconditionally I expect this to also influence the behaviour of TM.
Nitpicking & Conclusion
=======================
I feel like the documentation could explicitly mention the difference
between TMMONTH and TAMMONTH (i.e., mentioning genitive and nominative
like the Locale docs you mentioned do). I also think it would be
beneficial to
mention that this linguistic detail is specific to certain languages.
Furthermore, in general I feel like the code could have more comments.
The single comment /* TAM suffix - localized alternative month name */
I would rather put outside the if-else block and set TAM directly in
relation
to TM there.
All in all, this topic seems to have been a pain point for many people
as the discussion threads mentioned in the beginning attest. The patch
offers a solution to make glibc behaviour more predictable for users.
I see a very real use case here.
Best
Bernd
On 12/08/2026 09:13, Pavel Stehule wrote:
Hi
út 11. 8. 2026 v 17:14 odesílatel Pavel Stehule
<[email protected]> napsal:
út 11. 8. 2026 v 17:06 odesílatel Pavel Stehule
<[email protected]> napsal:
Hi
My customer reported an interesting issue. He needs translated
month name, and then he use
to_char(current_date, 'tmmonth');
Unfortunately, glibc returns nouns in the genitive case
instead of the nominative case.
This is a glibc feature from the 2.28 release. Genitive case
makes sense, when the result holds a day, but without it, it
is messy.
glibc has alternative month names, that can be taken by usage
placeholder '%OB' of function strftime.
https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/V1_chap07.html
- see alt_mon.
Can we enhance prefixes (maybe tmo) to be possible to use
alternative names?
example:
pavel@nemesis:~/src/orafce$ date +'%B'
srpna
pavel@nemesis:~/src/orafce$ date +'%OB'
srpen
pavel@nemesis:~/src/orafce$ LANG=C date +'%OB'
August
attached patch that implements 'TAM' modifier for data/timestamp
formatting
Regards
Pavel
Regards
Pavel
