On Fri, 21 Dec 2018 at 06:44, Tom Lane <t...@sss.pgh.pa.us> wrote: > I was distressed to discover via perf that 69% of the runtime of this > test now goes into match_eclasses_to_foreign_key_col(). That seems > clearly unacceptable.
Agreed. That's pretty terrible. I looked at this a bit and see that match_eclasses_to_foreign_key_col() is missing any smarts to skip equivalence classes that don't have ec_relids bits for both rels. With that added the run-time is reduced pretty dramatically. I've only tested with a debug build as of now, but I get: Unpatched: $ pgbench -n -T 60 -f query.sql postgres latency average = 18411.604 ms Patched: latency average = 8748.177 ms Going by my profiler this drops match_eclasses_to_foreign_key_col() down to just 10% of total planner time for this query. The new bms_is_member() call is pretty hot inside that function though. -- David Rowley http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services
speed_up_matching_fkeys_to_eclasses.patch
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