Re: Parallel Seq Scan

From: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Kouhei Kaigai <kaigai(at)ak(dot)jp(dot)nec(dot)com>, Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com>, Gavin Flower <GavinFlower(at)archidevsys(dot)co(dot)nz>, Jeff Davis <pgsql(at)j-davis(dot)com>, Andres Freund <andres(at)2ndquadrant(dot)com>, Amit Langote <amitlangote09(at)gmail(dot)com>, Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>, Fabrízio Mello <fabriziomello(at)gmail(dot)com>, Thom Brown <thom(at)linux(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Parallel Seq Scan
Date: 2015-09-26 07:39:54
Message-ID: CAA4eK1Ka72sm1QR3oBGdkhJTKYk3KHi-nB6AszewsRMiFYfdLA@mail.gmail.com
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On Sat, Sep 26, 2015 at 5:52 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>
> On Fri, Sep 25, 2015 at 12:00 AM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
wrote:
> > I think initPlan will work with the existing patches as we are always
> > executing it in master and then sending the result to workers. Refer
> > below code in funnel patch:
>
> Sure, *if* that's what we're doing, then it will work. But if an
> initPlan actually attaches below a funnel, then it will break.
>

Currently, it's considered for initPlan of only left tree of Funnel, however
if we want to push multiple nodes under Funnel, then it won't work as
it is. I think even if we want to make that work, we would need to
traverse the whole tree under Funnel and do what currently is done for
each of the initPlan we encounter. In general, I think the idea of
passing the results of initPlan to workers seems like the right way
of dealing with initPlans and by the way this was a suggestion made
by you sometime back.

With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com

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