Re: CHECK Constraint Deferrable

On Monday, October 2, 2023, Andreas Joseph Krogh <andreas(at)visena(dot)com> wrote:

> På fredag 07. juli 2023 kl. 13:50:44, skrev Dilip Kumar <
> dilipbalaut(at)gmail(dot)com>:
>
> On Wed, Jul 5, 2023 at 3:08 PM Himanshu Upadhyaya
> <upadhyaya(dot)himanshu(at)gmail(dot)com> wrote:
> >
> > Hi,
> >
> > Currently, there is no support for CHECK constraint DEFERRABLE in a
> create table statement.
> > SQL standard specifies that CHECK constraint can be defined as
> DEFERRABLE.
>
> I think this is a valid argument that this is part of SQL standard so
> it would be good addition to PostgreSQL. So +1 for the feature.
>
> But I am wondering whether there are some real-world use cases for
> deferred CHECK/NOT NULL constraints? I mean like for foreign key
> constraints if there is a cyclic dependency between two tables then
> deferring the constraint is the simplest way to insert without error.
>
>
>
> The real-world use case, at least for me, is when using an ORM. For large
> object-graphs ORMs have a tendency to INSERT first with NULLs then UPDATE
> the “NOT NULLs” later.
>
> “Rewrite the ORM” is not an option for most of us…
>
Between this and Vik comment it sounds like we should probably require a
patch in this area to solve both the not null and check constraint deferral
omissions then, not just one of them (alternatively, let’s solve the not
null one first).

David J.