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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