Re: [HACKERS] PG 10 release notes

On Wed, Apr 26, 2017 at 07:38:05PM +0530, Amit Kapila wrote:
> >> I have already mentioned the commit id (5e6d8d2b).  Text can be "Allow
> >> queries containing subplans to execute in parallel".  We should also
> >> mention in some way that this applies only when the query contains
> >> uncorrelated subplan.
> >
> > Sorry but I don't know what that means, and if I don't know, others
> > might not either.
> >
> 
> regression=# explain (costs off) select count(*) from tenk1 where
> (two, four) not in     (select hundred, thousand from tenk2 where
> thousand > 100);
>                       QUERY PLAN
> ------------------------------------------------------
>  Finalize Aggregate
>    ->  Gather
>          Workers Planned: 2
>          ->  Partial Aggregate
>                ->  Parallel Seq Scan on tenk1
>                      Filter: (NOT (hashed SubPlan 1))
>                      SubPlan 1
>                        ->  Seq Scan on tenk2
>                              Filter: (thousand > 100)
> (9 rows)
> 

Oh, so non-correlated subqueries can be run in parallel.  Yes, that is
something we should have in the release notes.  How is this?
Author: Robert Haas <rhaas@postgresql.org>2017-02-14 [5e6d8d2bb] Allow parallel workers to execute subplans.Allow
non-correlatedsubqueries to be run in parallel (Amit Kapila)
 

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