Re: pgsql: Add parallel-aware hash joins.

So this patch has been in place for two weeks, the buildfarm has still
got the measles, and we're entering the January commitfest with a lot
of other work to get done. I realize that the two weeks were mostly
holiday time, but it's time to have some urgency about clearing the
buildfarm failures.

As best I understand, the remaining failures simply arise from
an unstable regression test case and aren't teaching us anything
of value. I propose that for the moment, we simply remove the
failing query from join.sql. We can put it back when there's
reason to think it will pass everywhere.

regards, tom lane