Re: Allow parallel plan for referential integrity checks?

On Mon, Feb 7, 2022 at 5:26 AM Frédéric Yhuel <frederic.yhuel@dalibo.com> wrote:
> I noticed that referential integrity checks aren't currently
> parallelized. Is it on purpose?

It's not 100% clear to me that it is safe. But on the other hand, it's
also not 100% clear to me that it is unsafe.

Generally, I only added CURSOR_OPT_PARALLEL_OK in places where I was
confident that nothing bad would happen, and this wasn't one of those
places. It's something of a nested-query environment -- your criterion
#6. How do we know that the surrounding query isn't already parallel?
Perhaps because it must be DML, but I think it must be more important
to support parallel DML than to support this.

I'm not sure what the right thing to do here is, but I think it would
be good if your patch included a test case.

--
Robert Haas
EDB: http://www.enterprisedb.com