Horton

Re: [HACKERS] why not parallel seq scan for slow functions

Michael Paquier <michael.paquier@gmail.com>

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From: Michael Paquier <michael.paquier@gmail.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>, Jeff Janes <jeff.janes@gmail.com>, Thomas Munro <thomas.munro@enterprisedb.com>, Amit Khandekar <amitdkhan.pg@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2017-11-29T05:01:26Z
Lists: pgsql-hackers 
On Fri, Nov 10, 2017 at 4:42 AM, Robert Haas <robertmhaas@gmail.com> wrote:
> On Thu, Nov 9, 2017 at 3:47 AM, Amit Kapila <amit.kapila16@gmail.com> wrote:
>> I think I understood your concern after some offlist discussion and it
>> is primarily due to the inheritance related check which can skip the
>> generation of gather paths when it shouldn't.  So what might fit
>> better here is a straight check on the number of base rels such that
>> allow generating gather path in set_rel_pathlist, if there are
>> multiple baserels involved.  I have used all_baserels which I think
>> will work better for this purpose.
>
> Yes, that looks a lot more likely to be correct.
>
> Let's see what Tom thinks.

Moved to next CF for extra reviews.
-- 
Michael

Commits

  1. Rewrite the code that applies scan/join targets to paths.

  2. Teach create_projection_plan to omit projection where possible.

  3. Make the upper part of the planner work by generating and comparing Paths.