Horton

Re: why not parallel seq scan for slow functions

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: 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: 2017-11-09T19:42:17Z
Lists: pgsql-hackers 
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.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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.