@Override
 protected TypeComparator<PojoContainingTuple> createComparator(boolean ascending) {
   Assert.assertTrue(type instanceof CompositeType);
   CompositeType<PojoContainingTuple> cType = (CompositeType<PojoContainingTuple>) type;
   ExpressionKeys<PojoContainingTuple> keys =
       new ExpressionKeys<PojoContainingTuple>(new String[] {"theTuple.*"}, cType);
   boolean[] orders = new boolean[keys.getNumberOfKeyFields()];
   Arrays.fill(orders, ascending);
   return cType.createComparator(
       keys.computeLogicalKeyPositions(), orders, 0, new ExecutionConfig());
 }