On Wed, Dec 21, 2016 at 6:36 AM, Ashutosh Bapat <ashutosh.ba...@enterprisedb.com> wrote: > I am starting this as a separate thread for this since the declarative > partitioning thread has many issues reported and it's better to keep > this discussion separate from the issues reported on that thread. > > While expanding inheritance, any inheritance hierarchy is flattened > out including partition hierarchy. Partition-wise joins can be > employed if the joining tables have the same partitioning scheme and > have equi-join clauses on the partition keys. If two multi-level > partitioned tables are joined, the partition-wise join can be > percolated down to the levels up to which the partition schemes match > and suitable clauses are available. E.g. if two multi-level > partitioned table have matching partitioning schemes at the top-most > level, but not below that, we may join the topmost level partitions > pair-wise, but not partitions on the lower levels. In general, we may > use partition-wise join for the matching parts of partition hierarchy > and in the parts that do not match, use join between append relations. > Not always it will be efficient to execute partition-wise joins upto > the last levels of partition hierarchy, even if partition-wise join > can be employed. It might be possible that executing partition-wise > joins for only certain parts of partition hierarchy is efficient and > join of appends is efficient in the rest of the parts. > > In order to decide whether partition-wise join is efficient for a join > between given partitioned partition, we need to identify its > subpartitions. Similarly when a join between partitioned partition can > not use partition-wise join but some other partitions can, we need to > identify the subpartitions of that partition, so that they can be > appended together before joining. That information is lost while > expanding RTE. It looks like we need to retain partitioning hierarchy > in order to implement partition-wise joins between multi-level > partitioned tables. > > An earlier version of Amit's partition support patches had code to > retain partitioning hierarchy but it seems it was removed per > discussion at . I agree with that decision.
I can't quite figure out what the point of this email is. What did you want to discuss? -- 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