Robert Haas ccd8f97922 postgres_fdw: Consider requesting sorted data so we can do a merge join. ... When use_remote_estimate is enabled, consider adding ORDER BY to the query we sending to the remote server so that we can use that ordered data for a merge join. Commit f18c944b61 arranges to push down the query pathkeys, which seems like the case mostly likely to be a win, but testing shows this can sometimes win, too. For a regular table, we know which indexes are present and therefore test whether the ordering provided by each such index is useful. Here, we take the opposite approach: guess what orderings would be useful if they could be generated cheaply, and then ask the remote side what those will cost. Ashutosh Bapat, with very substantial cosmetic revisions by me. Also reviewed by Rushabh Lathia.		2015-12-22 13:46:40 -05:00
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postgres_fdw.sql	postgres_fdw: Consider requesting sorted data so we can do a merge join.	2015-12-22 13:46:40 -05:00