Re: Foreign join pushdown vs EvalPlanQual

From: Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>
To: fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp
Cc: kaigai(at)ak(dot)jp(dot)nec(dot)com, robertmhaas(at)gmail(dot)com, tgl(at)sss(dot)pgh(dot)pa(dot)us, pgsql-hackers(at)postgresql(dot)org, shigeru(dot)hanada(at)gmail(dot)com
Subject: Re: Foreign join pushdown vs EvalPlanQual
Date: 2015-11-05 01:02:16
Message-ID: 20151105.100216.227427686.horiguchi.kyotaro@lab.ntt.co.jp
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Hi, I've caught up again.

> OK, so if we all agree that the joined-tuple optimization is just an
> option for the case where all the component tables use ROW_MARK_COPY,
> I'd propose to leave that for 9.6.

I still think that ExecScan is called under EPQ recheck without
EQP tuple for the *scan*.

The ForeignScan can be generated for a join and underlying
foreign scans and such execution node returns what the core
deesn't expect for any scan node. This is what I think is the
root cause of this problem.

So, as the third way, I propose to resurrect the abandoned
ForeinJoinState seems to be for the unearthed requirements. FDW
returns ForeignJoinPath, not ForeignScanPath then finally it
becomes ForeignJoinState, which is handeled as a join node with
no doubt.

What do you think about this?

regards,

--
Kyotaro Horiguchi
NTT Open Source Software Center

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