Re: missing warning in pg_import_system_collations

On 10/09/2021 01:37, Tom Lane wrote:
> Another approach we could take is to deem the comment incorrect and
> just remove it, codifying the current behavior of silently ignoring
> unrecognized encodings.  The reason that seems like it might be
> appropriate is that the logic immediately below this bit silently
> ignores encodings that are known but are frontend-only:
> 
>              if (!PG_VALID_BE_ENCODING(enc))
>                  continue;        /* ignore locales for client-only encodings */
> 
> It's sure not very clear to me why one case deserves a message and the
> other not.  Perhaps they both do, which would lead to adding another
> DEBUG1 message here.

I'm not an expert in locales, but I think it makes some sense to be 
silent about encodings we have consciously decided to ignore as we have 
them in our tables, but marked them as frontend-only 
(!PG_VALID_BE_ENCODING(enc)).
Just like it makes sense to do give a debug-level warning about 
encodings seen in locale -a output but not recognized by us at all 
(pg_get_encoding_from_locale(localebuf, false) < 0).

Therefore I think your patch with duplicated error message is better 
than what we have currently. I don't see how adding debug-level messages 
about skipping frontend-only encodings would be of any significant use here.

Unless someone more experienced in locales' subtleties would like to 
chime in.

-- 
Anton Voloshin
Postgres Professional, The Russian Postgres Company
https://postgrespro.ru