On Wed, Oct 4, 2017 at 11:34 AM, Robert Haas <robertmh...@gmail.com> wrote: > + Enables or disables the query planner's use of partition-wise join > + plans. When enabled, it spends time in creating paths for joins > between > + partitions and consumes memory to construct expression nodes to be > used > + for those joins, even if partition-wise join does not result in the > + cheapest path. The time and memory increase exponentially with the > + number of partitioned tables being joined and they increase linearly > + with the number of partitions. The default is <literal>off</>. > > I think this is too scary and too much technical detail. I think you > could just say something like: Enables or disables use of > partition-wise join, which allows a join between partitioned tables to > be performed by joining the matching partitions. Partition-wise join > currently applies only when the join conditions include all the > columns of the partition keys, which must be of the same data type and > have exactly matching sets of child partitions. Because > partition-wise join planning can use significantly increase CPU time > and memory usage during planning, the default is <literal>off</>.
Not enough caffeine, obviously: should have been something like -- Because partition-wise join can significantly increase the CPU and memory costs of planning... -- 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
