On Tue, Dec 1, 2015 at 11:30 AM, Bruce Momjian <br...@momjian.us> wrote: > On Tue, Nov 3, 2015 at 06:05:11PM +0000, Robert Haas wrote: >> postgres_fdw: Add ORDER BY to some remote SQL queries. >> >> If the join problem's entire ORDER BY clause can be pushed to the >> remote server, consider a path that adds this ORDER BY clause. If >> use_remote_estimate is on, we cost this path using an additional >> remote EXPLAIN. If not, we just estimate that the path costs 20% >> more, which is intended to be large enough that we won't request a >> remote sort when it's not helpful, but small enough that we'll have >> the remote side do the sort when in doubt. In some cases, the remote >> sort might actually be free, because the remote query plan might >> happen to produce output that is ordered the way we need, but without >> remote estimates we have no way of knowing that. >> >> It might also be useful to request sorted output from the remote side >> if it enables an efficient merge join, but this patch doesn't attempt >> to handle that case. > > Does this complete FDW join pushdown?
It's the most important part, but we may want to do other things. See http://www.postgresql.org/message-id/CAFjFpRfeKHiCmwJ72p4=zvuzrqsau9tbfyw7vwr-5ppvrcb...@mail.gmail.com -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-committers mailing list (pgsql-committers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-committers
