Re: Identity columns should own only one sequence

On Sun, Apr 14, 2019 at 05:51:47PM +0200, Laurenz Albe wrote:
> test=> INSERT INTO ser (id) VALUES (DEFAULT);
> ERROR: more than one owned sequence found

Yes this should never be user-triggerable, so it seems that we need to
fix and back-patch something if possible.

> I propose that we check if there already is a dependent sequence
> before adding an identity column.

That looks awkward. Souldn't we make sure that when dropping the
default associated with a serial column then the dependency between
the column and the sequence is removed instead? This implies more
complication in ATExecColumnDefault().

> The attached patch does that, and also forbids setting the ownership
> of a sequence to an identity column.
>
> I think this should be backpatched.

Could you add some test cases with what you think is adapted?
--
Michael