On 07/26/2011 09:08 AM, Robert Haas wrote:
On Tue, Jul 26, 2011 at 4:12 AM, Nikhil Sontakke
<nikhil.sonta...@enterprisedb.com>  wrote:
Yeah.  I think it's good that there's a barrier to blindly dropping a
constraint that may be important to have on children, but there should
be a way to override that.
Hmmm, but then it does open up the possibility of naive users shooting
themselves in the foot. It can be easy to conjure up a
parent-only-constraint that does not gel too well with its children. And
that's precisely why this feature was added in the first place..
Yeah, but I think we need to take that chance.  At the very least, we
need to support the equivalent of a non-inherited CHECK (false) on
parent tables.

Indeed. I usually enforce that with a trigger that raises an exception, but of course that doesn't help at all with constraint exclusion, and I saw a result just a few weeks ago (I forget the exact details) where it appeared that the plan chosen was significantly worse because the parent table wasn't excluded, so there's a non-trivial downside from having this restriction.



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