Re: Foreign join pushdown vs EvalPlanQual

I wrote:
>> As Robert mentioned in [1], I think that if we're inside EPQ,
>> pushed-down quals and/or pushed-down joins should be locally rechecked
>> in the same way as other cases such as IndexRecheck. So, I'll propose
>> the updated version of the patch.

On 2015/10/16 18:48, Kouhei Kaigai wrote:
> You have never answered my question for two months.
>
> I never deny to execute the pushed-down qualifiers locally.
> It is likely the best tactics in most cases.
> But, why you try to enforce all the people a particular manner?
>
> Here are various kind of FDW drivers. How do you guarantee it is
> the best solution for all the people? It is basically impossible.
> (Please google "Probatio diabolica")
>
> You try to add two special purpose fields in ForeignScan;
> fdw_recheck_plan and fdw_recheck_quals.
> It requires FDW drivers to have pushed-down qualifier in a particular
> data format, and also requires FDW drivers to process EPQ recheck by
> alternative local plan, even if a part of FDW drivers can process
> these jobs by its own implementation better.
>
> I've repeatedly pointed out this issue, but never get reasonable
> answer from you.
>
> Again, I also admit alternative plan may be reasonable tactics for
> most of FDW drivers. However, only FDW author can "decide" it is
> the best tactics to handle the task for their module, not us.
>
> I don't think it is a good interface design to enforce people to
> follow a particular implementation manner. It should be discretion
> of the extension.

I think that if you think so, you should give at least one concrete
example for that. Ideally accompanied by a demo of how that works well.

Best regards,
Etsuro Fujita