On 2016/03/19 4:51, Robert Haas wrote:
On Thu, Mar 17, 2016 at 7:00 AM, Etsuro Fujita
<fujita.ets...@lab.ntt.co.jp> wrote:
So, I'd like to propose: (1) when tableoids are
requested from the remote server, postgres_fdw sets valid values for
them locally, instead (core should support that?)


Sure.

and (2) when any of
xmins, xmaxs, cmins, and cmaxs are requested, postgres_fdw gives up
pushing down foreign joins.  (We might be able to set appropriate values
for them locally the same way as for tableoids, but I'm not sure it's
worth complicating the code.)  I think that would be probably OK,
because users wouldn't retrieve any such columns in practice.

Now that seems like the wrong reaction.  I mean, aren't these just
going to be 0 or something?  Refusing to push the join down seems
strange.

OK, I'll modify the patch so that the join is pushed down even if any of xmins, xmaxs, cmins, and cmaxs are requested. Do you think which one should set values for these as well as tableoids, postgres_fdw or core?

Best regards,
Etsuro Fujita




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