Re: NOT ENFORCED constraint feature

On 2025-Mar-27, Amul Sul wrote:

> On Thu, Mar 27, 2025 at 6:28 PM Peter Eisentraut <peter(at)eisentraut(dot)org> wrote:

> > That said, is there a simpler way? Patch 0003 appears to add a lot of
> > complexity. Could we make this simpler by saying, if you have otherwise
> > matching constraints with different enforceability, make this an error.
> > Then users can themselves adjust the enforceability how they want to
> > make it match.
>
> We can simply discard this patch, as it still reflects the correct
> behavior. It creates a new constraint without affecting the existing
> constraint with differing enforceability on the child. I noticed
> similar behavior with deferrability -- when it differs, the
> constraints are not merged, and a new constraint is created on the
> child. Let me know your thoughts so I can avoid squashing patch 0006.

I didn't read that patch and I don't know what level of complexity we're
talking about, but the idea of creating a second constraint beside an
existing one itches me. I'm pretty certain most users would rather not
end up with redundant constraints that only differ in enforceability or
whatever other properties. I failed to realize that this was happening
when adding FKs on partitioned tables, and I now think it was a mistake.
(As I said in some previous thread, I'd rather have this kind of
situation raise an error so that the user can do something about it,
rather than silently moving ahead with a worse solution like creating a
redundant constraint.)

--
Álvaro Herrera PostgreSQL Developer — https://www.EnterpriseDB.com/
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