On Sun, 2024-06-16 at 11:27 +0200, Karsten Hilbert wrote:
> > the collations themselves
> > are defined by an external library, so the implementation is shared.
>
> Which in turn means I cannot at all truly _remove_ collations
> from a cluster at the SQL level, only make them invisible
> (and thereby not-to-be-used) inside a particular database by
> removing them from pg_collations via DROP COLLATION, right ?
As far as PostgreSQL is concerned, you can remove them.
You cannot remove the C library, but a PostgreSQL user can only use
the collation if there is a collation defined in PostgreSQL.
(Actually, that's not quite true: in CREATE DATABASE, you can use
ICU collations. That does not depend on the collations defined in
pg_collation.)
Also, there is nothing that keeps a user from running CREATE COLLATION
to create a collation in a schema where the user can CREATE objects.
I wouldn't try too hard to make it impossible for users to use a
collation you don't want. Dropping the collations is good enough to
keep a user from using the wrong collation by mistake.
Yours,
Laurenz Albe