Re: Custom/Foreign-Join-APIs (Re: [v9.5] Custom Plan API)

On Wed, Mar 18, 2015 at 2:34 AM, Kouhei Kaigai <kaigai(at)ak(dot)jp(dot)nec(dot)com> wrote:
> So, overall consensus for the FDW hook location is just before the set_chepest()
> at standard_join_search() and merge_clump(), isn't it?

Yes, I think so.

> Let me make a design of FDW hook to reduce code duplications for each FDW driver,
> especially, to identify baserel/joinrel to be involved in this join.

Great, thanks!

One issue, which I think Ashutosh alluded to upthread, is that we need
to make sure it's not unreasonably difficult for foreign data wrappers
to construct the FROM clause of an SQL query to be pushed down to the
remote side. It should be simple when there are only inner joins
involved, but when there are all outer joins it might be a bit
complex. It would be very good if someone could try to write that
code, based on the new hook locations, and see how it turns out, so
that we can figure out how to address any issues that may crop up
there.

--
Robert Haas
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