On Wed, Jan 07, 2015 at 03:01:20PM -0500, Stephen Frost wrote:
> * Robert Haas (robertmhaas@gmail.com) wrote:
> > On Wed, Jan 7, 2015 at 4:04 AM, Dean Rasheed <dean.a.rasheed@gmail.com> wrote:
> > > I think the policies applied should depend on the path taken, so if it
> > > does an INSERT, then only the INSERT CHECK policy should be applied
> > > (after the insert), but if it ends up doing an UPDATE, I would expect
> > > the UPDATE USING policy to be applied (before the update) and the
> > > UPDATE CHECK policy to be applied (after the update). I would not
> > > expect the INSERT CHECK policy to be applied on the UPDATE path.
> >
> > I agree.
>
> I can certainly understand the appeal of this approach, but I don't
> think it makes sense. Consider what happens later on down the road,
> after the code has been written and deployed using INSERT .. ON CONFLICT
> UPDATE where 99% of the time only one path or the other is taken. Then
> the other path is taken and suddenly the exact same command and row ends
> up returning errors. Additional testing should have been done to check
> if that happens, of course, but I really don't like the idea that the
> exact same command, with the exact same policies, would succeed or fail,
> due to policies, based on the data in the database.
There's precedent. Unique constraints, for example.
Cheers,
David.
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