On 2016-01-25 8:35 PM, Peter Geoghegan wrote:
> On Mon, Jan 25, 2016 at 2:00 AM, Marko Tiikkaja <marko@joh.to> wrote:
>> FWIW, I would've expected to be able to do RETURNING excluded.foo which
>> would have been NULL in case of INSERT, and the value from the updated tuple
>> otherwise. But that doesn't seem to work.
>
> The problem with that approach is that it makes both the target table
> and the excluded pseudo table visible from within RETURNING. If we
> were to do that, virtually every use of INSERT with both an ON
> CONFLICT DO UPDATE clause and a RETURNING clause breaks. That's
> because any unqualified column reference becomes ambiguous ("Did you
> mean target.foo or excluded.foo?").
Surely there's a way to make this work so that EXCLUDED is a special
tuple whose fields are normally not in scope, but can be accessed
explicitly.
But this discussion belongs to -HACKERS, as you said upthread.
.m