Hi, On 2017-07-26 20:12:56 +1200, Thomas Munro wrote: > Here is a new version of my parallel-aware hash join patchset.
Yay! Working on reviewing this. Will send separate emails for individual patch reviews. > 2. Simplified costing. There is now just one control knob > "parallel_synchronization_cost", which I charge for each time the > participants will wait for each other at a barrier, to be set high > enough to dissuade the planner from using Parallel Hash for tiny hash > tables that would be faster in a parallel-oblivious hash join. > Earlier ideas about modelling the cost of shared memory access didn't > work out. Hm. You say, "didn't work out" - could you expand a bit on that? I'm quite doubtful that justaccounting for barriers will be good enough. > I'll report on performance separately. Looking forward to that ;) Greetings, Andres Freund -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers