Re: WIP: Upper planner pathification

I wrote:
> Amit Kapila <amit.kapila16@gmail.com> writes:
>> I think here we should use rel->consider_parallel to set parallel_safe as
>> is done in create_mergejoin_path.

> Well, the "rel" is going to be an upperrel that will have been
> manufactured by fetch_upper_rel, and it will contain no useful
> information about parallelism, so I'm not real sure what that
> would buy.

Ah, after further study I found where this issue is handled for
joinrels.  I think you're probably right that it'd be a good idea
to include rel->consider_parallel when setting parallel_safe in
upper paths.  In the short term that will have the effect of
marking all upper paths as parallel-unsafe, but that's at least a
safe default that we can improve later.
        regards, tom lane