Re: parallel.sgml for Gather with InitPlans

On Mon, May 7, 2018 at 11:34 PM, Amit Kapila <amit.kapila16@gmail.com> wrote:
> Is this correct?  See below example:

That's not a counterexample to what I wrote.  When parallelism is
used, the InitPlan has to be attached to a parallel-restricted node,
and it is: Gather.  It's true that in the serial plan it's attached to
the Seq Scan, but that doesn't prove anything.  Saying that something
is parallel-restricted is a statement about where parallelism can be
used; it says nothing about what happens without parallelism.

> I think we can cover InitPlan and Subplans that can be parallelized in
> a separate section "Parallel Subplans" or some other heading.  I think
> as of now we have enabled parallel subplans and initplans in a
> limited, but useful cases (as per TPC-H benchmark) and it might be
> good to cover them in a separate section.  I can come up with an
> initial patch (or I can review it if you write the patch) if you and
> or others think that makes sense.

We could go that way, but what I wrote is short and -- I think -- accurate.

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