Re: [HACKERS] EvalPlanQual behaves oddly for FDW queries involvingsystem columns

Hi Andres,

(2019/02/28 5:33), Andres Freund wrote:
> On 2015-05-12 14:24:34 -0400, Tom Lane wrote:
>> I did a very basic update of your postgres_fdw patch to test this with,
>> and attach that so that you don't have to repeat the effort.  I'm not sure
>> whether we want to try to convert that into something committable.  I'm
>> afraid that the extra round trips involved in doing row locking this way
>> will be so expensive that no one really wants it for postgres_fdw.  It's
>> more credible that FDWs operating against local storage would have use
>> for it.
>
> Fujita-san, do you know of any FDWs that use this?

No, I don't.

> I'm currently
> converting the EPQ machinery to slots, and in course of that I (with
> Horiguchi-san's help), converted RefetchForeignRow to return a slot. But
> there's currently no in-core user of this facility...  I guess I can
> rebase the preliminary postgres_fdw patch here, but it bitrotted
> significantly.

I'll rebase that patch and help the testing, if you want me to.

> I also feel like there should be some test coverage for
> an API in a nontrivial part of the code...

Yeah, but as mentioned above, the row-locking API is provided for FDWs 
operating against local storage, which we don't have in core, unfortunately.

Best regards,
Etsuro Fujita