-> Parallel Seq Scan on fact_agg_2015_12 (cost=0.00..743769.76 rows=4221741 width=12)
Great! Thanks for testing this.
If you run EXPLAIN ANALYZE on this with the 6 workers, does the actual number of Gather rows come out at 105? I'd just like to get an idea of my cost estimate for the Gather are going to be accurate for real world data sets.