Re: Parallel Append implementation

On 16 February 2017 at 20:37, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:

> I'm not sure that it's going to be useful to make this logic very
> complicated. I think the most important thing is to give 1 worker to
> each plan before we give a second worker to any plan. In general I
> think it's sufficient to assign a worker that becomes available to the
> subplan with the fewest number of workers (or one of them, if there's
> a tie)

> without worrying too much about the target number of workers for that subplan.

The reason I have considered per-subplan workers is , for instance, so
that we can respect the parallel_workers reloption set by the user for
different tables. Or for e.g., subquery1 is a big hash join needing
more workers, and subquery2 is a small table requiring quite lesser
workers, it seems to make sense to give more workers to subquery1.