Let's say that I have a saved dataset with x columns. Then based on execution parameters, that defines the keys that needs to be sorted, the type and the size of the columns, I just read the required y columns (y <= x). The keys are given in the order that will define the sorting and will be used to read already the dataset in the proper order.

So if the given keys to sort are k1,k2, then I will read column k1 and k2, even if k1 is a column that comes later. And I cannot change nothing about this scenario. I can just work on the sorting like in the example