Re: incorrect (incomplete) description for "alter domain"

On Mon, Jul 29, 2024 at 11:17:41AM -0400, Tom Lane wrote:
> I wrote:
> > I think the page is technically correct, but I'm inclined to duplicate
> > this text from the CREATE DOMAIN page:
>
> > where domain_constraint is:
> > [ CONSTRAINT constraint_name ]
> > { NOT NULL | NULL | CHECK (expression) }
>
> > rather than making readers go look that up.
>
> Actually, there *is* a bug in the description, because experimentation
> shows that CREATE DOMAIN accepts NULL in this syntax (as advertised)
> but ALTER DOMAIN does not. We could alternatively decide that that's
> a code bug and make ALTER DOMAIN take it, but I don't think it's worth
> any effort (and this behavior may actually have been intentional, too).
> I think we should just add
>
> where domain_constraint is:
>
> [ CONSTRAINT constraint_name ]
> { NOT NULL | CHECK (expression) }
>
> to the ALTER DOMAIN page, and then remove the claim that it's
> identical to CREATE DOMAIN.

I have written the attached patch to document this. I assume this
should be backpatched to PG 12.

--
Bruce Momjian <bruce(at)momjian(dot)us> https://momjian.us
EDB https://enterprisedb.com

When a patient asks the doctor, "Am I going to die?", he means
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