Re: Tables cannot have INSTEAD OF triggers

On 2015-04-01 13:15:26 -0400, Tom Lane wrote:
> Andres Freund <andres(at)anarazel(dot)de> writes:
> > On 2015-04-01 12:46:05 -0400, Robert Haas wrote:
> >> So, the idea is that INSTEAD OF would behave like BEFORE but the tuple
> >> it returns wouldn't actually be inserted? That wasn't clear to me
> >> from the OP, but I guess it would be a reasonable way to go.
>
> > I'm not sure what the OP intended, but to me that's pretty much the only
> > reasonable definition of INSTEAD OF for tables that I can think of.
>
> If you have such a trigger, it's impossible to insert any rows, which
> means the table doesn't need storage, which means it may as well be a
> view, no? So this still seems to me like a wart not a useful feature.
> I think it would create confusion because a table with such a trigger
> would act so much unlike other tables.

For one you can't easily add partitions to a view (and
constraint_exclusion = partition IIRC doesn't work if you use UNION ALL),
for another there's WHEN for triggers that should allow dealing with
that.

Greetings,

Andres Freund