Re: Partitioning feature ...

We already have system triggers -- the FK triggers.  I don't think we've
had all that much trouble with them.
   

In the case of the FK triggers, it's intentional (and maybe even
documented) that users should be able to place their own triggers before
or after the FK triggers.

If it's documented I think it's well hidden ;-) ISTM that the fact that we implement FK constraints via triggers is really an implementation detail, not something the user should be encouraged to mess with.

 Is there a good reason why partitioning
triggers should be different?    

Probably not. ISTM that the scheme should turn tgisconstraint into a multi-valued item (tgkind: 'u' = userland, 'c'= constraint, 'p' = partition or some such).