Re: [HACKERS] Add support for tuple routing to foreign partitions

On 2017/08/26 1:43, Robert Haas wrote:
> On Sun, Aug 20, 2017 at 11:25 PM, Etsuro Fujita
> <fujita.etsuro@lab.ntt.co.jp> wrote:
>>> I agree, but I wonder if we ought to make it work first using the
>>> existing APIs and then add these new APIs as an optimization.
>>
>> I'm not sure that's a good idea because that once we support INSERT
>> tuple-routing for foreign partitions, we would have a workaround: INSERT
>> INTO partitioned_table SELECT * from data_table where data_table is a
>> foreign table defined for an input file using file_fdw.
> 
> That's true, but I don't see how it refutes the point I was trying to raise.

My concern is: the existing APIs can really work well for any FDW to do 
COPY tuple-routing?  I know the original version of the patch showed the 
existing APIs would work well for postgres_fdw but nothing beyond.  For 
example: the original version made a dummy Query/Plan only containing a 
leaf partition as its result relation, and passed it to 
PlanForeignModify, IIRC.  That would work well for postgres_fdw because 
it doesn't look at the Query/Plan except the result relation, but might 
not for other FDWs that look at more stuff of the given Query/Plan and 
do something based on that information.  Some FDW might check to see 
whether the Plan is to do INSERT .. VALUES with a single VALUES sublist 
or INSERT .. VALUES with multiple VALUES sublists, for optimizing remote 
INSERT, for example.

Best regards,
Etsuro Fujita