Re: creating objects in pg_catalog

Robert Haas <robertmhaas@gmail.com> writes:
> Right now, you can't directly create a relation (table, index,
> composite type) in the pg_catalog schema, but you can create a
> non-relation (function, domain, etc.) in the pg_catalog schema.

Surely this is true only for superusers.  Superusers can do whatever
they want anyway, no?

> Tabula raza, I'd argue for getting tough on this, and error out on any
> attempt to get a user-created SQL object into pg_catalog by any means,
> unless allow_system_table_mods is set.

allow_system_table_mods is mainly intended to prevent people from
altering the schemas of system catalogs, since it's more than likely
that the backend C code will fail (nastily) to cope with such changes.
I don't think it follows that we should prevent superusers from doing
things that are perfectly safe, like adding new functions in pg_catalog.

It's very likely that the specific restrictions enforced by
allow_system_table_mods could stand a fresh look, but I don't agree
with the idea of radically changing its charter.  Nor do I think we
need to put training wheels on superusers for any changes that aren't
demonstrably likely to result in unrecoverable database corruption.
        regards, tom lane