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Subject: Re: Order changes in PG16 since ICU introduction
From: "Daniel Verite" <daniel@manitou-mail.org>
To: "Jeff Davis" <pgsql@j-davis.com>
Cc: Peter Eisentraut
 <peter.eisentraut@enterprisedb.com>,
 Andrew Gierth <andrew@tao11.riddles.org.uk>,
 Tom Lane <tgl@sss.pgh.pa.us>,
 pgsql-hackers@lists.postgresql.org
In-Reply-To: <5111ffef640ec7ed5b75d9791dd18d821e96c31e.camel@j-davis.com>
Date: Tue, 06 Jun 2023 15:09:59 +0200
Message-Id: <45f0cd77-9c85-4c5e-9396-adbccdb635e2@manitou-mail.org>
Archived-At: <https://www.postgresql.org/message-id/45f0cd77-9c85-4c5e-9396-adbccdb635e2%40manitou-mail.org>
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	Jeff Davis wrote:

> New patch series attached. I plan to commit 0001 and 0002 soon, unless
> there are objections.
>=20
> 0001 causes the "C" and "POSIX" locales to be treated with
> memcmp/pg_ascii semantics in ICU, just like in libc. We also
> considered a new "none" provider, but it's more invasive, and we can
> always reconsider that in the v17 cycle.

FWIW I don't quite see how 0001 improve things or what problem it's
trying to solve.

0001 creates exceptions throughout the code so that when an ICU
collation has a locale name "C" or "POSIX" then it does not behave
like an ICU collation, even though pg_collation.collprovider=3D'i'
To me it's neither desirable nor necessary that a collation that
has collprovider=3D'i' is diverted to non-ICU semantics.

Also in the current state, this diversion does not apply to initdb.

"initdb --icu-locale=3DC" with 0001 applied reports this:

   Using language tag "en-US-u-va-posix" for ICU locale "C".
   The database cluster will be initialized with this locale configuration:
     provider:	  icu
     ICU locale:  en-US-u-va-posix
     LC_COLLATE:  fr_FR.UTF-8
     [...]

and "initdb --locale=3DC" reports this:

   Using default ICU locale "fr_FR".
   Using language tag "fr-FR" for ICU locale "fr_FR".
   The database cluster will be initialized with this locale configuration:
     provider:	  icu
     ICU locale:  fr-FR
     LC_COLLATE:  C
     [...]

Could you elaborate a bit more on what 0001 is meant to achieve, from
the point of view of the user?


Best regards,
--=20
Daniel V=E9rit=E9
https://postgresql.verite.pro/
Twitter: @DanielVerite