BUG #18251: Incorrect DROP VIEW pg_catalog.* behavior

Hi,

On Sun, Dec 17, 2023 at 09:44:33AM +0000, PG Bug reporting form wrote:

When i try to drop and create system view, i get following behavior:

postgres=# DROP VIEW pg_catalog.pg_config;
DROP VIEW

postgres=# CREATE OR REPLACE VIEW pg_catalog.pg_config AS
SELECT pg_config.name, pg_config.setting
FROM pg_config() pg_config(name, setting);
ERROR: permission denied to create "pg_catalog.pg_config"
DETAIL: System catalog modifications are currently disallowed.

That's somewhat expected. System catalog modifications are only prevented
globally at the creation side, I guess mostly because we don't want user to
e.g. create an index or a trigger on a system catalog just to realize that it
won't be maintained, and things like that.

The fact that you can drop a system view is because you're using a superuser
connection, and there are so many things you can do as a superuser to mess up
the instance so there wouldn't be much value disallowing just this specific
case.

I'm not sure, but it's look strange.
When i connect to template1, i can use droped views. But if drop view on
template1 problem repeats.

That's not surprising. You always need to use a database to create a new one.
The only different between a template database and a normal database is the
permissions needed on the source database side.