Re: Foreign join pushdown vs EvalPlanQual

On 2015/11/24 2:41, Robert Haas wrote:
> On Fri, Nov 20, 2015 at 12:11 AM, Kouhei Kaigai <kaigai@ak.jp.nec.com> wrote:
>> One subplan means FDW driver run an entire join sub-tree with local
>> alternative sub-plan; that is my expectation for the majority case.

> What I'm imagining is that we'd add handling that allows the
> ForeignScan to have inner and outer children.  If the FDW wants to
> delegate the EvalPlanQual handling to a local plan, it can use the
> outer child for that.  Or the inner one, if it likes.  The other one
> is available for some other purposes which we can't imagine yet.  If
> this is too weird, we can only add handling for an outer subplan and
> forget about having an inner subplan for now.  I just thought to make
> it symmetric, since outer and inner subplans are pretty deeply baked
> into the structure of the system.

I'd vote for only allowing an outer subplan.

Best regards,
Etsuro Fujita