Re: What is the extent of FDW join pushdown support in 9.5?

> The 9.5 release notes contain this promising but cryptic item:
> 
> - Allow foreign data wrappers and custom scans to implement join
> pushdown (KaiGai Kohei)
> 
> As phrased, this seems to mean, "it can be done, but we haven't done
> it".  But there is no link to any documentation that explains how to do
> this.  The commit that appears to have added this feature touches
> postgres_fdw, but neither the documentation nor the tests show anything
> about this feature, and I haven't been able to reproduce anything that
> would seem to indicate anything like this is at work.
> 
> So what is the actual extent of this feature?
>
It says these enhancement on interface allows extensions to implement
join operation in their own way (including remote join in case of FDW),
however, enhancement of postgres_fdw is not yet upstreamed.

So, how about the description below? It focuses on interface enhancement.

- Allow extensions to implement join in their own way using foreign data wrappers and customer scan interface.

Thanks,
--
NEC Business Creation Division / PG-Strom Project
KaiGai Kohei <kaigai@ak.jp.nec.com>