Re: Guidance on INSERT RETURNING order

On Fri, Apr 14, 2023, at 11:17 PM, Tom Lane wrote:
> Federico <cfederico87(at)gmail(dot)com> writes:
>> Would something like what was proposed by Mike Bayer be considered?
>
>>> A new token called "tuple_order" or something
>>>
>>> INSERT INTO table (a, b, c) VALUES ((1, 2, 3), (4, 5, 6), ...) RETURNING table.id, inserted.tuple_order
>>>
>>> tuple_order would be incrementing values 1, 2, 3, 4, 5, ... which correlate the each row delivered by RETURNING to each entry in the VALUES clause, in the order they were stated in that VALUES clause, that is entry (1, 2, 3) would be tuple_order 1, entry (4, 5, 6) would be tuple order 2, etc.
>
> As proposed, I don't think so. Something over in the RETURNING clause has
> exactly no connection to VALUES. What do you do if it's INSERT ... SELECT
> and there are several VALUES clauses down inside the SELECT?

in my "plan", the token would not be supported and an error would be raised.

>
> There is some prior art in this area, though. See the more-or-less
> SQL-standard WITH ORDINALITY option for functions-in-FROM. It seems to me
> that it could be plausible to attach WITH ORDINALITY to a VALUES clause,
> which would give you a rock-solid connection between the VALUES rows and
> the ordinality-column values, and then you could include that column in
> RETURNING.

I appreciate this idea! Any kind of keyword / syntax that frees us from having to round-trip additional data to the database and/or generate more complex syntaxes for certain kinds of default generation schemes would simplify the approach.