Planner improvements

A collection of improvements to the EPAS planner.

The improvements include a higher assignment of parallel workers, a better row-estimate for Subquery Scan plan nodes when used in parallel, a better costing model for mixed workloads, and better row count estimates for joins where the statistics collector is not providing enough information.

Settings

swarm64da.enable_planner_improvements (boolean)

Enables or disables the planner improvements. The default is on.

swarm64da.maximize_parallel_workers (boolean)

Enables or disables overriding the number of parallel workers used during query execution and maintenance operations. The maximum is limited by the max_parallel_workers_per_gather setting for query execution and the max_parallel_maintenance_workers setting for maintenance operations. The default is on.