From: | Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> |
---|---|
To: | k(dot)knizhnik(at)postgrespro(dot)ru |
Cc: | robertmhaas(at)gmail(dot)com, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: FDW and parallel execution |
Date: | 2017-04-04 10:29:09 |
Message-ID: | 20170404.192909.129892049.horiguchi.kyotaro@lab.ntt.co.jp |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
Hi,
At Sun, 02 Apr 2017 16:30:24 +0300, Konstantin Knizhnik <k(dot)knizhnik(at)postgrespro(dot)ru> wrote in <58E0FCF0(dot)2070603(at)postgrespro(dot)ru>
> Hi hackers and personally Robet (you are the best expert in both
> areas).
> I want to ask one more question concerning parallel execution and FDW.
> Below are two plans for the same query (TPC-H Q5): one for normal
> tables, another for FDW to vertical representation of the same data.
> FDW supports analyze function and is expected to produce the similar
> statistic as for original tables.
<big explain>
> The plans look very similar, but first one is parallel and second -
> not.
> My FDW provides implementation for IsForeignScanParallelSafe which
> returns true.
> I wonder what can prevent optimizer from using parallel plan in this
> case?
Parallel execution requires partial paths. It's the work for
GetForeignPaths of your FDW.
regards,
--
Kyotaro Horiguchi
NTT Open Source Software Center
From | Date | Subject | |
---|---|---|---|
Next Message | Mithun Cy | 2017-04-04 10:33:47 | Re: [POC] A better way to expand hash indexes. |
Previous Message | Amit Kapila | 2017-04-04 10:29:05 | Re: Page Scan Mode in Hash Index |