On 8 May 2014 04:33, Kouhei Kaigai <kaigai@ak.jp.nec.com> wrote:
> In case when it replaced join relations by ForeignScan, it will be almost
> same as expected ForeignScan with join-pushed down. Unlike usual table scan,
> it does not have actual relation definition on catalog, and its result
> tuple-slot is determined on the fly.
> One thing different from the remote-join is, this ForeignScan node may have
> sub-plans locally, if FDW driver (e.g GPU execution) may have capability on
> Join only, but no relation scan portion.
> So, unlike its naming, I want ForeignScan to support to have sub-plans if
> FDW driver supports the capability.
From here, it looks exactly like pushing a join into an FDW. If we had
that, we wouldn't need Custom Scan at all.
I may be mistaken and there is a critical difference. Local sub-plans
doesn't sound like a big difference.
Have we considered having an Optimizer and Executor plugin that does
this without touching core at all?
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