Re: [HACKERS] [COMMITTERS] pgsql: Simplify plpgsql's check for simple expressions.

Tom Lane <tgl@sss.pgh.pa.us> writes:
> Simplify plpgsql's check for simple expressions.
> ...
> https://git.postgresql.org/pg/commitdiff/00418c61244138bd8ac2de58076a1d0dd4f539f3

The buildfarm members that are running force_parallel_mode = regress
are not happy with this.  Apparently, even a trivial SELECT <expression>
can be turned into a Gather plan if force_parallel_mode says so.

I assume (haven't looked) that I could hack the plpgsql code to prevent
generating a parallel plan when it's decided the command is a simple
SELECT.  But I wonder whether that's the right place to fix it.  Does
it ever make sense to parallelize a plan that can't possibly benefit?
IOW I am not sure that we should carry force_parallel_mode this far.
        regards, tom lane