Re: missing possibility to use alternative translated month names in to_char function

Hi Pavel,

On 8/18/26 8:47 PM, Pavel Stehule wrote:
> Hi
>
> so 15. 8. 2026 v 14:03 odesílatel Bernd Reiß <bd_reiss(at)gmx(dot)at <mailto:bd_reiss(at)gmx(dot)at>> napsal:
>
> Hi again,
>
> thanks for the updated patch.
> > TAMMON is not implemented, because glibc doesn't provide an
> > alternative form for abbreviated month names.
> > It is a question if it is better to raise an error, return a non
> > alternative name or just ignore this flag. I have not strong
> > opinion about this. Inside DCH_to_char the prefix TM is ignored when
> > it is not used. So I did the same.
> The Locale standard actually mentions abbreviated alternative month
> names as
> "ab_alt_mon" (see [1]). I tested this by setting your TAMMONTH strftime
> call to '%Ob'.
> If we set the locale to Russian and call the function for May this
> actually returns
> an abbreviated version of the month name:
>
> Breakpoint 1, cache_locale_time () at pg_locale.c:772
> 772           if (strftime_l(bufptr, MAX_L10N_DATA, "%Ob", timeinfo,
> locale) <= 0)
> (gdb) n
> 774                     bufptr += MAX_L10N_DATA;
> (gdb) print bufptr
> $4 = 0x7ffde4554630 "май"
>
> Compared to the TMMON form of May in Russian this actually makes a
> difference:
>
> postgres=# set lc_time='ru_RU.UTF8';
> SET
> postgres=# select to_char('2026-05-01'::date, 'TMMON');
>   to_char
> ---------
>   МАЯ
> (1 row)
>
> postgres=# select to_char('2026-05-01'::date, 'TAMMONTH');
>   to_char
> ---------
>   МАЙ
> (1 row)
>
> Again, TAMMONTH uses %Ob here. So I would argue for implementing the
> abbreviated
> forms too.
>
>
> I implemented it - please check

LGTM. I compiled it and it works as expected. I also like the introduction of
the get_localized_*_months functions. However, this leads to suffix_len being
declared and set but never used in the DCH_MONTH, DCH_Month, and DCH_month
cases (as well as for the abbreviated equivalents) in DCH_from_char. Passing
NULL and guarding in the functions would be an option to avoid this. However,
I don't feel strongly about this.

In DCH_to_char I think you forgot to refactor this if statement for the
MON/Mon/mon cases?

if (strlen(str) <= (n->key->len + TM_SUFFIX_LEN) * DCH_MAX_ITEM_SIZ)
strcpy(s, str);

>
> Please check updated patch
>

With the if statements cleaned up this is a +1 for Ready for Committer from me.

Best
Bernd