Tom Lane schrieb am 27.05.2016 um 15:48:
Thomas Kellerer <spam_eater@xxxxxxx> writes:
while playing around with the parallel aggregates and seq scan in
9.6beta I noticed that Postgres will stop using parallel plans when
cpu_tuple_cost is set to a very small number.
If you don't reduce the parallel-plan cost factors proportionally,
it's not very surprising that reducing that would tend to bias the
planner away from using parallel plans. See parallel_setup_cost and
parallel_tuple_cost.
Ah, thanks. That makes sense.
The low value for cpu_tuple_cost was actually a typo.
Adjusting parallel_tuple_cost does bring back the parallel plan.
Thomas
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