Re: pgsql: Add a new GUC and a reloption to enable inserts in parallel-mode

On Wed, Mar 24, 2021 at 2:00 AM Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:
>
> On 2021-Mar-23, Robert Haas wrote:
>
> > Likewise, the XXX comment you added to max_parallel_hazard_walker
> > claims that some of the code introduced there is to compensate for an
> > unspecified bug in the rewriter. I'm a bit skeptical that the comment
> > is correct, and there's no way to find out because the comment doesn't
> > say what the bug supposedly is, but let's just say for the sake of
> > argument that it's true. Well, you *could* have fixed the bug, but
> > instead you hacked around it, and in a relatively expensive way that
> > affects every query with a CTE in it whether it can benefit from this
> > patch or not. That's not a responsible way of maintaining the core
> > PostgreSQL code.
>
> I think the CTE bug is this one:
>
> https://www.postgresql.org/message-id/flat/CAJcOf-fAdj=nDKMsRhQzndm-O13NY4dL6xGcEvdX5Xvbbi0V7g(at)mail(dot)gmail(dot)com
>
> while I can't disagree with the overall conclusion that it seems safer
> to revert parallel INSERT/SELECT given the number of alleged problems,
>

Agreed. I'll revert the patch and respond to some of the points here
with my thoughts.

--
With Regards,
Amit Kapila.