On Fri, Apr 14, 2023 at 8:17 PM Tom Lane <tgl@xxxxxxxxxxxxx> wrote:
Federico <cfederico87@xxxxxxxxx> 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?
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 suppose breaking the restriction that only columns present on the insertion-table can be returned is a possible option that also solves another infrequent request.
Adding with ordinality to the values clause seems like an independent feature that has merit on its own for the same reason SRFs have that option.
Ultimately, though, whatever is supplying the rows to the insert is going to have to supply them in some order, and the returning clause can simply modify the executor to perform an initial pass over the input data in order to assign the ordering indexes before allowing for parallelism, and then sort again on the way out. User-space does/should not need to create data for this purpose. A top-level values query should not need to be specified with ordinality while subquery ones would be hidden from the mechanism, the parent query being responsible for any ordering that is desired.
David J.
