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RE: Order changes in PG16 since ICU introduction

Regina Obe <lr@pcorp.us>

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From: "Regina Obe" <lr@pcorp.us>
To: "'Tom Lane'" <tgl@sss.pgh.pa.us>, "'Peter Eisentraut'" <peter.eisentraut@enterprisedb.com>
Cc: "'Sandro Santilli'" <strk@kbt.io>, <pgsql-hackers@lists.postgresql.org>, "'Jeff Davis'" <pgsql@j-davis.com>
Date: 2023-04-21T17:37:25Z
Lists: pgsql-hackers 
> Peter Eisentraut <peter.eisentraut@enterprisedb.com> writes:
> > If the database is created with locale provider ICU, then lc_collate
> > does not apply here, so the result might be correct (depending on what
> > locale you have set).
> 
> FWIW, an installation created under LANG=C defaults to ICU locale en-US-u-
> va-posix for me (see psql \l), and that still sorts as expected on my
RHEL8 box.
> We've not seen buildfarm problems either.
> 
> I am wondering however whether this doesn't mean that all our carefully
> coded fast paths for C locale just went down the drain.  Does the ICU code
> have any of that?  Has any performance testing been done to see what
impact
> this change had on C-locale installations?  (The current code coverage
report
> for pg_locale.c is not encouraging.)
> 
> 			regards, tom lane

Just  another metric.

On my mingw64 setup, I built a test database on PG16 (built with icu
support) and PG15 (no icu support)

CREATE DATABASE test TEMPLATE=template0 ENCODING = 'UTF8' LC_COLLATE = 'C'
LC_CTYPE = 'C';

I think the above is the similar setup we have when testing.

On PG15 

SELECT '+' <  '-' ;  returns true

On PG 16 returns false

For PG 16, to strk's point, you have to do: to get a true
SELECT '+' COLLATE "C" <  '-'  COLLATE "C";


I would expect since I'm initializing my db in collate C they would both
behave the same

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Introduce "builtin" collation provider.

  2. ICU: do not convert locale 'C' to 'en-US-u-va-posix'.

  3. initdb: change default --locale-provider back to libc.

  4. CREATE DATABASE: make LOCALE apply to all collation providers.

  5. Remove read-only server settings lc_collate and lc_ctype

  6. ICU: use uloc_getDefault() for initdb.

  7. Doc fixes for commit 1e16af8ab5.

  8. Doc: fix some rendering problems in the PDF docs build.

  9. Doc improvements for language tags and custom ICU collations.

  10. ICU: check for U_STRING_NOT_TERMINATED_WARNING.

  11. Reduce icu_validation_level default to WARNING.

  12. Revert "ICU: do not convert locale 'C' to 'en-US-u-va-posix'."

  13. Fix initdb --no-locale.

  14. Avoid character classification in regex escape parsing.