Re: Built-in CTYPE provider

On Tue, 2024-01-09 at 14:17 -0800, Jeremy Schneider wrote:
> I think we missed something in psql, pretty sure I applied all the
> patches but I see this error:
>
> =# \l
> ERROR:  42703: column d.datlocale does not exist
> LINE 8:   d.datlocale as "Locale",
>

Thank you. I'll fix this in the next patch set.

> This is interesting. Jeff your original email didn't explicitly show
> any
> other initcap() results, but on Ubuntu 22.04 (glibc 2.35) I see
> different results:
>
> =# SELECT initcap('axxE áxxÉ DŽxxDŽ Džxxx džxxx');
>          initcap
> --------------------------
>  Axxe Áxxé DŽxxdž DŽxxx DŽxxx
>
> =# SELECT initcap('axxE áxxÉ DŽxxDŽ Džxxx džxxx' COLLATE C_UTF8);
>          initcap
> --------------------------
>  Axxe Áxxé Džxxdž Džxxx Džxxx

The reason for this difference is because libc doesn't support
titlecase. In the next patch set, I'll not use titlecase (only
uppercase/lowercase even for initcap()), and then it will match libc
100%.

> The COLLATE sql syntax feels awkward to me. In this example, we're
> just
> using it to attach locale info to the string, and there's not
> actually
> any collation involved here. Not sure if COLLATE comes from the
> standard, and even if it does I'm not sure whether the standard had
> upper/lowercase in mind.

The standard doesn't use the COLLATE clause for case mapping, but also
doesn't offer any other mechanism to, e.g., get case mapping according
to the "tr_TR" locale.

I think what Postgres does here, re-purposing the COLLATE clause to
allow tailoring of case mapping, is imperfect but reasonable. My
proposal doesn't change that.

Regards,
Jeff Davis