On Thu, Aug 31, 2017 at 3:36 AM, Amit Langote <langote_amit...@lab.ntt.co.jp> wrote: > ISTM, the primary motivation for the EIBO patch at this point is to get > the partitions ordered in a predictable manner so that the partition-wise > join patch and update partition key patches could implement certain logic > using O (n) algorithm rather than an O (n^2) one.
That's part of it, but not the whole thing. For example, BASIC partition-wise join only needs a predictable order, not a bound-ordered one. But the next step is to be able to match up uneven bounds - e.g. given [1000, 2000), [3000, 4000), [5000, 6000) on one side and [1100, 2100), [2900,3900), and [5500,5600) on the other side, we can still make it work. That greatly benefits from being able to iterate through all the bounds in order. > Neither of them depend > on the actual order in the sense of, say, sticking a PathKey to the > resulting Append. Perhaps, the patch to"Make the optimiser aware of > partitions ordering" [1] will have to consider this somehow; maybe by > limiting its scope to only the cases where the root partitioned table is > range partitioned. I think that doing a depth-first traversal as I've done here avoids the need to limit it to that case. If we did a breadth-first traversal anything that was subpartitioned would end up having the subpartitions at the end instead of in the sequence, but the depth-first traversal avoids that issue. -- 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
