Function get_best_fitting_window 

pub fn get_best_fitting_window(
    window_exprs: &[Arc<dyn WindowExpr>],
    input: &Arc<dyn ExecutionPlan>,
    physical_partition_keys: &[Arc<dyn PhysicalExpr>],
) -> Result<Option<Arc<dyn ExecutionPlan>>, DataFusionError>

Constructs the best-fitting windowing operator (a WindowAggExec or a BoundedWindowExec) for the given input according to the specifications of window_exprs and physical_partition_keys. Here, best-fitting means not requiring additional sorting and/or partitioning for the given input.

• A return value of None represents that there is no way to construct a windowing operator that doesn’t need additional sorting/partitioning for the given input. Existing ordering should be changed to run the given windowing operation.
• A Some(window exec) value contains the optimal windowing operator (a WindowAggExec or a BoundedWindowExec) for the given input.