Re: Not Null Constraint vs Query Planning

On Mon, Mar 2, 2020, 12:30 Vik Fearing <vik(at)postgresfriends(dot)org> wrote:

> On 02/03/2020 18:09, Don Seiler wrote:
> > The REAL reason for this is that I'm wondering if I created a NOT NULL
> > check constraint with "NOT VALID" would that then NOT be considered in
> such
> > a "short-circuit" case until I ran the VALIDATE CONSTRAINT on it?
> Perhaps I
> > should have just asked this in its own thread but I started diving into
> the
> > query plan thing.
>
> You cannot do this because NOT NULL isn't a real constraint (meaning it
> does not appear in pg_constraint). There have been several attempts to
> make it a real constraint over the years but so far nothing has come of
> them

Using the check constraint method seemed to allow for the "not valid" step.
I'm curious what the difference is between a NOT NULL check constraint
versus setting the column to NOT NULL (assuming both are validated).

Don.