Re: ALTER COLUMN ... SET EXPRESSION to alter stored generated column's expression

On Mon, Dec 18, 2023 at 3:01 PM Peter Eisentraut <peter(at)eisentraut(dot)org>
wrote:

> On 11.12.23 13:22, Amul Sul wrote:
> >
> > create table t1 (a int, b int generated always as (a + 1) stored);
> > alter table t1 add column c int, alter column b set expression as (a
> > + c);
> > ERROR: 42703: column "c" does not exist
> >
> > I think intuitively, this ought to work. Maybe just moving the new
> > pass
> > after AT_PASS_ADD_COL would do it.
> >
> >
> > I think we can't support that (like alter type) since we need to place
> > this new
> > pass before AT_PASS_OLD_INDEX & AT_PASS_OLD_CONSTR to re-add indexes and
> > constraints for the validation.
>
> Could we have AT_PASS_ADD_COL before AT_PASS_OLD_*? So overall it would be
>
> ...
> AT_PASS_ALTER_TYPE,
> AT_PASS_ADD_COL, // moved
> AT_PASS_SET_EXPRESSION, // new
> AT_PASS_OLD_INDEX,
> AT_PASS_OLD_CONSTR,
> AT_PASS_ADD_CONSTR,
> ...
>
> This appears to not break any existing tests.
>

(Sorry, for the delay)

Agree. I did that change in 0001 patch.

Regards,
Amul