On Tue, Apr 21, 2015 at 9:38 AM, Amit Kapila <amit.kapil...@gmail.com> wrote: > On Mon, Apr 20, 2015 at 10:08 PM, Robert Haas <robertmh...@gmail.com> wrote: >> >> On Tue, Apr 7, 2015 at 11:58 PM, Amit Kapila <amit.kapil...@gmail.com> >> wrote: >> > One disadvantage of retaining parallel-paths could be that it can >> > increase the number of combinations planner might need to evaluate >> > during planning (in particular during join path evaluation) unless we >> > do some special handling to avoid evaluation of such combinations. >> >> Yes, that's true. But the overhead might not be very much. In the >> common case, many baserels and joinrels will have no parallel paths >> because the non-parallel paths is known to be better anyway. Also, if >> parallelism does seem to be winning, we're probably planning a query >> that involves accessing a fair amount of data, > > Am I understanding right that by above you mean to say that retain the > parallel and non-parallel path only if parallel-path wins over non-parallel > path?
Yes. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
