Horton

Re: Built-in CTYPE provider

Jeremy Schneider <schneider@ardentperf.com>

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From: Jeremy Schneider <schneider@ardentperf.com>
To: pgsql-hackers@lists.postgresql.org, "Davis, Jeff" <jefdavj@amazon.com>
Date: 2023-12-21T00:04:39Z
Lists: pgsql-hackers 
On 12/20/23 3:47 PM, Jeremy Schneider wrote:
> On 12/5/23 3:46 PM, Jeff Davis wrote:
>> CTYPE, which handles character classification and upper/lowercasing
>> behavior, may be simpler than it first appears. We may be able to get
>> a net decrease in complexity by just building in most (or perhaps all)
>> of the functionality.
> 
> I'll be honest, even though this is primarily about CTYPE and not
> collation, I still need to keep re-reading the initial email slowly to
> let it sink in and better understand it... at least for me, it's complex
> to reason through. 🙂
> 
> I'm trying to make sure I understand clearly what the user impact/change
> is that we're talking about: after a little bit of brainstorming and
> looking through the PG docs, I'm actually not seeing much more than
> these two things you've mentioned here: the set of regexp_* functions PG
> provides, and these three generic functions. That alone doesn't seem
> highly concerning.

I missed citext, which extends impact to replace(), split_part(),
strpos() and translate().  There are also the five *_REGEX() functions
from the SQL standard which I assume are just calling the PG functions.

I just saw the krb_caseins_users GUC, which reminds me that PLs also
have their own case functions. And of course extensions. I'm not saying
any of this is in scope for the change here, but I'm just trying to wrap
my brain around all the places we've got CTYPE processing happening, to
better understand the big picture. It might help tease out unexpected
small glitches from changing one thing but not another one.

-Jeremy


-- 
http://about.me/jeremy_schneider

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.