On 26 October 2017 at 23:42, Antonin Houska <a...@cybertec.at> wrote: > David Rowley <david.row...@2ndquadrant.com> wrote: > >> Method 1: >> >> In set_append_rel_size() detect when just a single subpath would be >> added to the Append path. > > I spent some time reviewing the partition-wise join patch during the last CF > and have an impression that set_append_rel_size() is called too early to find > out how many child paths will eventually exist if Append represents a join of > a partitioned table. I think the partition matching takes place at later stage > and that determines the actual number of partitions, and therefore the number > of Append subpaths.
I understand that we must wait until set_append_rel_size() is being called on the RELOPT_BASEREL since partitions may themselves be partitioned tables and we'll only know what's left after we've recursively checked all partitions of the baserel. I've not studied the partition-wise join code yet, but if we've eliminated all but one partition in set_append_rel_size() then I imagine we'd just need to ensure partition-wise join is not attempted since we'd be joining directly to the only partition anyway. -- David Rowley http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
