Sort
Classes
- RowOrder
- Nulls smallest unless placed, NaN largest, -0.0 = 0.0, strings by bytes; ties keep input order.
- SortColumn
- SortKey
- One reference's sort key over a batch: a rank per row (0 null, 1 value, 2 NaN) and the value it orders by within rank 1, compared with $flag (SORT_NUMERIC, SORT_STRING or SORT_REGULAR).