order-by optimization via max-heap popping instead of final sort

A performance suggestion, based on unproven, rough reading of the code...

When doing an ORDER BY ... OFFSET x LIMIT y, a max-heap that can grow to size x+y is maintained. At the very end, a final sort.Sort() is performed on the collected items.

If that's the correct understanding, this might be optimized where instead of a final sorting of the items (which can have up to x+y number of entries), the max-heap can instead be Pop()'ed by y number of times to retrieve the sorted results.