Re: Support NOT VALID / VALIDATE constraint options for named NOT NULL constraints

Hi Alvaro,

I’ve consolidated all the changes and attached the latest version of the
patch, which
includes the updates submitted by Jian for pg_dump as well.

Patch 0001 contains changes to MergeWithExistingConstraint to fix the
marking on local constraints.
Patch 0002 includes support for NOT NULL NOT VALID, corresponding pg_dump
changes, test cases,
                   and documentation updates.

Please let me know if anything is missing or needs further adjustment.

Thanks,



On Thu, Apr 3, 2025 at 1:37 PM Alvaro Herrera <alvherre@alvh.no-ip.org>
wrote:

> On 2025-Apr-03, Peter Eisentraut wrote:
>
> > It occurred to me that we will also want to have NOT NULL NOT ENFORCED
> > constraints eventually.  As we have discussed elsewhere, the NOT
> > ENFORCED state is closely related to the NOT VALID state.  So that
> > should probably be considered in the design here.
>
> Yeah, I don't think there's time to shoehorn NOT ENFORCED status for
> not-null constraints.  I'd guess that it'd take at least a couple of
> weeks to make that work.
>
> > Reading up on this again now, I'm confused about putting the NOT VALID
> > state for not-null constraints into pg_attribute.  We have catalogued
> > not-null constraints now, so we can put metadata for them into
> > pg_constraint!  And we have NOT VALID and NOT ENFORCED flags in
> > pg_constraint already.
> >
> > So what is the purpose of the attnotnullvalid field?  In the latest
> posted
> > patch, I don't see this column used in the executor for the actual
> > constraint checking.  So is this all merely for clients to understand the
> > constraint metadata?  If we add more metadata for not-null constraints,
> do
> > we need to add a new pg_attribute flag for each one?  That doesn't seem
> > right.
>
> The new flag is there for quick access by get_relation_info.  We could
> easily not have it otherwise, because clients don't need it, but its
> lack would probably make planning measurably slower because it'd have to
> do syscache access for every single not-null constraint to figure out if
> it's valid or not.
>
> --
> Álvaro Herrera        Breisgau, Deutschland  —
> https://www.EnterpriseDB.com/
> "Hay quien adquiere la mala costumbre de ser infeliz" (M. A. Evans)
>


-- 
Rushabh Lathia