Re: wCTE: why not finish sub-updates at the end, not the beginning?

"Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov> writes:
> Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Given that we've decided to run the modifying sub-queries all with
>> the same command counter ID, they are logically executing "in
>> parallel".

>> Just run the main plan and let it pull tuples from the CTEs as
>> needed.

> On the face of it, that sounds like it has another benefit you
> didn't mention -- it sounds like it's much more conducive to
> allowing parallel processing, if (when?) we eventually move in that
> direction. It might even be a good case for an initial, limited
> implementation.

Yeah. Most of the executor is in principle parallelizable at the
plan-node level (ignoring the obvious and severe implementation
problems with parallelizing *anything* in the backend). It's not
good for wCTE to be creating a user-visible assumption that certain
things will happen in a predefined order.

regards, tom lane