On Fri, May 12, 2017 at 12:38 PM, Robert Haas <robertmh...@gmail.com> wrote: > That is a good question. I think it basically amounts to this > question: is hash partitioning useful, and if so, for what?
Two words: parallel query. To get parallelism, one of the best approaches is dividing the data, then doing as much work as possible before combining it again. If you have hash partitions on some key, then you can do partition-wise joins or partition-wise aggregation on that key in parallel with no synchronization/communication overhead (until the final result). You've taken postgres pretty far in this direction already; hash partitioning will take it one step further by allowing more pushdowns and lower sync/communication costs. Some of these things can be done with range partitioning, too, but see my other message here: https://www.postgresql.org/message-id/CAMp0ubfNMSGRvZh7N7TRzHHN5tz0ZeFP13Aq3sv6b0H37fdcPg%40mail.gmail.com Regards, Jeff Davis -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers