anchor.diff:  %% from the row.
   -spec compile_select_col(DDL::#ddl_v1{}, ColumnSpec::any()) ->
                                   #single_sel_column{}.
  -compile_select_col(DDL, {{window_agg_fn, FnName}, [FnArg1]}) ->
  +compile_select_col(DDL, {{window_agg_fn, FnName}, [FnArg1]}) when is_atom(FnName) ->
       case riak_ql_window_agg_fns:start_state(FnName) of
           stateless ->
               {ColTypes1, IsValid1, Fn} = compile_select_col_stateless(DDL, FnArg1),
  
positive.code: 
  %% extract stateful functions from the selection
  -spec extract_stateful_functions2(selection(), integer(), [selection_function()]) ->
          {selection() | {return_state, integer()}, [selection_function()]}.
  extract_stateful_functions2({Op, ArgA1, ArgB1}, FinaliserLen, Fns1) ->
      {ArgA2, Fns2} = extract_stateful_functions2(ArgA1, FinaliserLen, Fns1),
      {ArgB2, Fns3} = extract_stateful_functions2(ArgB1, FinaliserLen, Fns2),
  
negative.code:     lists:keyreplace(Field, 1, TupleList, {Field, FieldType, NewVal}).
  
  -ifdef(TEST).
  -include_lib("eunit/include/eunit.hrl").
  
  %%
  %% Helper Fns for unit tests
  