Re: BUG #15324: Non-deterministic behaviour from parallelised sub-query

From: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
To: Dilip Kumar <dilipbalaut(at)gmail(dot)com>
Cc: Stephen Frost <sfrost(at)snowman(dot)net>, Robert Haas <robertmhaas(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Marko Tiikkaja <marko(at)joh(dot)to>, Andres Freund <andres(at)anarazel(dot)de>, Andrew Fletcher <andy(at)prestigedigital(dot)com>, PostgreSQL mailing lists <pgsql-bugs(at)lists(dot)postgresql(dot)org>
Subject: Re: BUG #15324: Non-deterministic behaviour from parallelised sub-query
Date: 2018-09-14 05:00:03
Message-ID: CAA4eK1K9ds+R+Q2Z-cSWYr+Jo1djonDjjRB+uWYZajyytpKLNw@mail.gmail.com
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On Thu, Sep 13, 2018 at 8:42 PM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
>
> On Thu, Sep 13, 2018 at 6:18 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >> >>
> >> >
> >> > I have rebased the HEAD patch and done some cosmetic changes like
> >> > improved the test by giving aliases to table names and modified the
> >> > comment a bit, otherwise, the core logic remains the same. As the
> >> > back-branch patches are just the matter of rebasing them, I will do
> >> > that before commit.
> >> >
> >> > I am still waiting for input, but if there is none, my plan is to
> >> > commit this in a day or two and back-patch it as well. Along with
> >> > this, I would also like to back-patch commit
> >> > 655393a022bd653e2b48dbf20b69236981e35195 for the reasons mentioned
> >> > above.
> >>
> >> I have reviewed and tested the patch. The patch looks fine to me and
> >> behaviour is as expected.
> >>

Thanks, pushed.

> >
> > Do you agree with my proposal to backpatch commit - 655393a022 to 9.6?
> >
>
> Although it was not giving any wrong output. However, this was a bug,
> due to which, it may not select the best parallel plan or completely
> miss some of the parallel paths so I will vote for backpatching it.
>

Okay, pushed the back-patch patch.

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

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