Horton

Re: Built-in CTYPE provider

Jeff Davis <pgsql@j-davis.com>

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From: Jeff Davis <pgsql@j-davis.com>
To: Jeremy Schneider <schneider@ardentperf.com>, Daniel Verite <daniel@manitou-mail.org>
Cc: Robert Haas <robertmhaas@gmail.com>, pgsql-hackers@postgresql.org
Date: 2024-01-09T22:31:59Z
Lists: pgsql-hackers 
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

Commits

  1. Support PG_UNICODE_FAST locale in the builtin collation provider.

  2. Support Unicode full case mapping and conversion.

  3. Fix test failures when language environment is not UTF-8.

  4. Add unicode_strtitle() for Unicode Default Case Conversion.

  5. Use version for builtin collations.

  6. Fix convert_case(), introduced in 5c40364dd6.

  7. Inline basic UTF-8 functions.

  8. Support C.UTF-8 locale in the new builtin collation provider.

  9. Fix another warning, introduced by 846311051e.

  10. Address more review comments on commit 2d819a08a1.

  11. Fix unreachable code warning from commit 2d819a08a1.

  12. Introduce "builtin" collation provider.

  13. Catalog changes preparing for builtin collation provider.

  14. Unicode case mapping tables and functions.

  15. Add Unicode property tables.

  16. Documentation update for Standard Collations.

  17. Cleanup for unicode-update build target and test.

  18. Shrink Unicode category table.

  19. Make some error strings more generic

  20. pg_upgrade: copy locale and encoding information to new cluster.

  21. Update Unicode data to Unicode 15.0.0

  22. Create a new type category for "internal use" types.