Miha Vrhovnik <miha(dot)vrhovnik(at)gmail(dot)com> writes:
> I'm so sorry, but I do not understand... Even if I force the schema in
> CREATE EXTENSION it still says that it already exists. (Tested on 12.4, but
> it's the same with 13, as I have tested it before)
> I'm missing something but the documentation doesn't state that I can only
> install extension once per database.
Extensions are not schema-qualified objects, so no, you cannot have
more than one instance per database.
regards, tom lane