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From: "Daniel Verite" <daniel@manitou-mail.org>
To: "Laurenz Albe" <laurenz.albe@cybertec.at>
Cc: Ron Johnson <ronljohnsonjr@gmail.com>,
 pgsql-general@lists.postgresql.org
Subject: Re: Choosing default collation/ctype
In-Reply-To: <bdce746ad6052774fbc0de138e7c4fcc77886e77.camel@cybertec.at>
Date: Tue, 05 May 2026 13:16:14 +0200
Message-Id: <f7b3c538-8e78-47f4-82f1-2e54e8da2f0b@manitou-mail.org>
Archived-At: <https://www.postgresql.org/message-id/f7b3c538-8e78-47f4-82f1-2e54e8da2f0b%40manitou-mail.org>
Precedence: bulk

	Laurenz Albe wrote:

> > So if you target Postgres 17+, C.UTF-8 from the builtin provider is
> > a better choice for UTF-8 databases than "C" .
>=20
> Yes, "builtin" and the "C" collation is the best default value.

But my point was that, no, it's not.
Let's show a concrete example with Postgres 18:

postgres=3D# create database dbc=20
template=3D'template0'
locale_provider=3D'builtin'
builtin_locale=3D'C'   ;
CREATE DATABASE

postgres=3D# \c dbc
You are now connected to database "dbc" as user "postgres".

dbc=3D# select upper('=E9t=E9');
 upper=20
-------
 =E9T=E9
(1 row)

It is not the correct uppercasing. On the other hand the "C.UTF-8"
locale, as opposed to "C", produces the correct result.

postgres=3D# create database dbcutf8=20
template=3D'template0'
locale_provider=3D'builtin'
builtin_locale=3D'C.UTF-8' ;
CREATE DATABASE

postgres=3D# \c dbcutf8
You are now connected to database "dbcutf8" as user "postgres".

dbcutf8=3D# select upper('=E9t=E9');
 upper=20
-------
 =C9T=C9
(1 row)


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