Re: pg_upgrade Python version issue on openSUSE

=?utf-8?Q?Paul_F=C3=B6rster?= <paul.foerster@gmail.com> writes:
> On 26. Sep, 2020, at 16:07, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> However, I don't understand how "drop extension plpythonu"
>> worked for you, given your previous query showing that
>> that extension wasn't installed.

> just checked with another 12.4. It's the same:

> postgres=# select * from pg_available_extension_versions where installed;
>   name   | version | installed | superuser | relocatable |   schema   | requires |                           comment
                          
>
---------+---------+-----------+-----------+-------------+------------+----------+--------------------------------------------------------------
>  plperlu | 1.0     | t         | t         | f           | pg_catalog |          | PL/PerlU untrusted procedural
language
>  dblink  | 1.2     | t         | t         | t           |            |          | connect to other PostgreSQL
databasesfrom within a database 
>  plpgsql | 1.0     | t         | f         | f           | pg_catalog |          | PL/pgSQL procedural language
>  plperl  | 1.0     | t         | f         | f           | pg_catalog |          | PL/Perl procedural language
> (4 rows)

> postgres=# drop extension plpythonu ;
> DROP EXTENSION
> postgres=# create extension plpython3u ;
> CREATE EXTENSION

Actually, now that I think about it, you're querying the wrong view.
I'm too lazy to check the source code right now, but I'm pretty sure
that pg_available_extension_versions is mostly driven off what control
files exist in the on-disk libdir.  But that may have little to do with
what's in the system catalogs.  You should have checked pg_extension,
or just "\dx" in psql.

            regards, tom lane