On Mon, Mar 13, 2017 at 7:46 AM, Robert Haas <robertmh...@gmail.com> wrote: > On Mon, Mar 13, 2017 at 4:59 AM, Amit Khandekar <amitdkhan...@gmail.com> > wrote: >> I agree that we should preferably have the non-partial plans started >> first. But I am not sure if it is really worth ordering the partial >> plans by cost. The reason we ended up not keeping track of the >> per-subplan parallel_worker, is because it would not matter much , >> and we would just equally distribute the workers among all regardless >> of how big the subplans are. Even if smaller plans get more worker, >> they will finish faster, and workers would be available to larger >> subplans sooner. > > Imagine that the plan costs are 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, and 10 > and you have 2 workers. > > If you move that 10 to the front, this will finish in 10 time units. > If you leave it at the end, it will take 15 time units.
Oh, never mind. You were only asking whether we should sort partial plans. That's a lot less important, and maybe not important at all. The only consideration there is whether we might try to avoid having the leader start in on a plan with a large startup cost. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers