Hello, I'm developing in MAL accessing commands and functions from C++ over the MAPI-library. My task is to delete some BUNs from a BAT. The problem: The BAT with some deleted BUNs has a different order than before. I do it the following way: c:bat[:oid,:int] := bbp.bind("joe"); slice:bat[:oid,:int] := algebra.slice(c,4,6); bat.delete(c,slice); The original BAT "joe": #-----------------# # h t # name # oid int # type #-----------------# [ 0@0, -1 ] [ 1@0, 2 ] [ 2@0, 3 ] [ 3@0, -1 ] [ 4@0, -2 ] <- to be deleted [ 5@0, 5 ] <- to be deleted [ 6@0, -2 ] <- to be deleted After delete: The original BAT "joe": #-----------------# # h t # name # oid int # type #-----------------# [ 3@0, -1 ] <- not in right order, why? [ 0@0, -1 ] [ 1@0, 2 ] [ 2@0, 3 ] Why is this so and how can I prevent MonetDB to change the order, while deleting BUNs. The order is important, because I'd like to work with position and slices to read my BUNs. Thanks for helping!