Horton

Re: Built-in CTYPE provider

Jeff Davis <pgsql@j-davis.com>

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From: Jeff Davis <pgsql@j-davis.com>
To: Peter Eisentraut <peter@eisentraut.org>, Daniel Verite <daniel@manitou-mail.org>
Cc: Robert Haas <robertmhaas@gmail.com>, Jeremy Schneider <schneider@ardentperf.com>, pgsql-hackers@postgresql.org
Date: 2024-03-27T22:13:55Z
Lists: pgsql-hackers 
On Tue, 2024-03-26 at 08:04 +0100, Peter Eisentraut wrote:
> The patch set v27 is ok with me, modulo (a) discussion about initcap 
> semantics, and (b) what collation to assign to ucs_basic, which can
> be 
> revisited later.

I held off on the refactoring patch for lc_{ctype|collate}_is_c().
There's an explicit "NB: pg_newlocale_from_collation is only supposed
to be called on non-C-equivalent locales" comment in DefineCollation().

What I'd like to do is make it possible to create valid pg_locale_t
objects out of C locales, which can be used anywhere a real locale can
be used. Callers can still check lc_{collate|ctype}_is_c() for various
reasons; but if they did call pg_newlocale_from_collation on a C locale
it would at least work for the pg_locale.h APIs. That would be a
slightly simpler and safer API, and make it easier to do the collation
version check consistently.

That's not very complicated, but it's a bit invasive and probably out
of scope for v17. It might be part of another change I had intended for
a while, which is to make NULL an invalid pg_locale_t, and use a
different representation to mean "use the server environment". That
would clean up a lot of checks for NULL.

For now, we'd still like to add the version number to the builtin
collations, so that leaves us with two options:

(a) Perform the version check in lc_{collate|ctype}_is_c(), which
duplicates some code and creates some inconsistency in how the version
is checked for different providers.

(b) Don't worry about it and just commit the version change in v27-
0001. The version check is already performed correctly on the database
without changes, even if the locale is "C". And there are already three
built-in "C" collations: "C", "POSIX", and UCS_BASIC; so it's not clear
why someone would create even more of them. And even if they did, there
would be no reason to give them a warning because we haven't
incremented the version, so there's no chance of a mismatch.

I'm inclined toward (b). Thoughts?

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.