| From: | Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com>, Kouhei Kaigai <kaigai(at)ak(dot)jp(dot)nec(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, Shigeru Hanada <shigeru(dot)hanada(at)gmail(dot)com> |
| Subject: | Re: Foreign join pushdown vs EvalPlanQual |
| Date: | 2015-11-24 03:44:38 |
| Message-ID: | 5653DD26.9040606@lab.ntt.co.jp |
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| Lists: | pgsql-hackers |
On 2015/11/24 2:41, Robert Haas wrote:
> On Fri, Nov 20, 2015 at 12:11 AM, Kouhei Kaigai <kaigai(at)ak(dot)jp(dot)nec(dot)com> wrote:
>> One subplan means FDW driver run an entire join sub-tree with local
>> alternative sub-plan; that is my expectation for the majority case.
> What I'm imagining is that we'd add handling that allows the
> ForeignScan to have inner and outer children. If the FDW wants to
> delegate the EvalPlanQual handling to a local plan, it can use the
> outer child for that. Or the inner one, if it likes. The other one
> is available for some other purposes which we can't imagine yet. If
> this is too weird, we can only add handling for an outer subplan and
> forget about having an inner subplan for now. I just thought to make
> it symmetric, since outer and inner subplans are pretty deeply baked
> into the structure of the system.
I'd vote for only allowing an outer subplan.
Best regards,
Etsuro Fujita
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