From: Tom Lane <tgl@sss.pgh.pa.us>
To: Etsuro Fujita <fujita.etsuro@lab.ntt.co.jp>
cc: Robert Haas <robertmhaas@gmail.com>,
        Pg Hackers <pgsql-hackers@postgresql.org>
Subject: Re: Oddity with parallel safety test for scan/join target in
 grouping_planner
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 <5C7908B9.5070407@lab.ntt.co.jp>
Comments: In-reply-to Etsuro Fujita <fujita.etsuro@lab.ntt.co.jp>
	message dated "Fri, 01 Mar 2019 19:26:01 +0900"
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Date: Fri, 08 Mar 2019 15:36:59 -0500
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Etsuro Fujita <fujita.etsuro@lab.ntt.co.jp> writes:
> (2019/02/28 0:52), Robert Haas wrote:
>> On Tue, Feb 26, 2019 at 7:26 AM Etsuro Fujita
>> <fujita.etsuro@lab.ntt.co.jp>  wrote:
>>> The parallel safety of the final scan/join target is determined from the
>>> grouping target, not that target, which [ is wrong ]

>> Your patch looks right to me.

> I think it would be better for you to take this one.  Could you?

I concur with Robert that this is a brown-paper-bag-grade bug in
960df2a97.  Please feel free to push (and don't forget to back-patch).

The only really interesting question is whether it's worth adding
a regression test for.  I doubt it; the issue seems much too narrow.
Usually the point of a regression test is to prevent re-introduction
of the same/similar bug, but what class of bugs would you argue
we'd be protecting against?

			regards, tom lane