ktds: explain how we apply orders

keytransform/keytransform.go

@@ -115,7 +115,14 @@ orders:
 			continue
 		case dsq.OrderByKey, *dsq.OrderByKey,
 			dsq.OrderByKeyDescending, *dsq.OrderByKeyDescending:
+			// if the key transform preserves order, we can delegate
+			// to the child datastore.
 			if orderPreserving {
+				// When sorting, we compare with the first
+				// Order, then, if equal, we compare with the
+				// second Order, etc. However, keys are _unique_
+				// so we'll never apply any additional orders
+				// after ordering by key.
 				child.Orders = child.Orders[:i+1]
 				break orders
 			}