Paul White takes us through a new trick the optimizer has learned:
The extended event
query_optimizer_batch_mode_agg_splitis provided to track when this new optimization is considered. The description of this event is:Occurs when the query optimizer detects batch mode aggregation is likely to spill and tries to split it into multiple smaller aggregations.
Other than that, this new feature hasn’t been documented yet. This article is intended to help fill that gap.
Read on as Paul fills that gap.