Hello,
The attached small patch is what I have in mind now.
fdwroutine->ExecForeignScan may be unset if the FDW does nothing
special. And all the FDW routine needs is the node.
> Subject: [PATCH] Allow substitute ExecScan body for ExecForignScan
>
> ForeignScan node may return joined tuple. This joined tuple cannot be
> handled properly by ExecScan during EQP recheck. This patch allows
> FDWs to give a special treat to such tuples.
regards,
> > One thing I can agree is, ForeignScan is enforced to use ExecScan,
> > thus some FDW driver may concern about this hard-wired logic.
> > If we try to make ForeignScan unbound from the ExecScan, I like to
> > suggest to revise ExecForeignScan, just invoke a callback; then
> > FDW driver can choose whether ExecScan is best or not.
>
> Agreed. Calling ExecScan unconditionally from ForeignScan is the
> cause of the root(?) cause I mentioned. Since there'd be no
> difference in data structure between Foreign(Join&Node), calling
> fdwroutine->ExecForeignScan() or something instaed of ExecScan()
> from ExecForeignScan could be the alternative and most promising
> solution for all problems in focus now.
--
Kyotaro Horiguchi
NTT Open Source Software Center
