anchor.diff:              (_, or_, Acc) ->
                   {skip, Acc};
               (Conditional, Filter, Acc) ->
  -            ?debugFmt("FILTER ~p", [Filter]),
  -            check_where_clause_is_possible_fold(DDL, Conditional, Filter, Acc)
  +                check_where_clause_is_possible_fold(DDL, Conditional, Filter, Acc)
           end, [], Filter1),
       lists:keystore(filter, 1, WhereProps, {filter,Filter2}).
   
  
positive.code: modify_where_key(TupleList, Field, NewVal) ->
      {Field, FieldType, _OldVal} = lists:keyfind(Field, 1, TupleList),
      lists:keyreplace(Field, 1, TupleList, {Field, FieldType, NewVal}).
  -include_lib("eunit/include/eunit.hrl").
  
  check_where_clause_is_possible(DDL, WhereProps) ->
      ?debugFmt("WHERE PROPS ~p", [WhereProps]),
      Filter1 = proplists:get_value(filter, WhereProps),
      {Filter2, _} = riak_ql_ddl:mapfold_where_tree(
          fun (_, and_, Acc) ->
  
negative.code:         false ->
              {eliminate, Acc}
      end;
  check_where_clause_is_possible_fold(_, _, Filter, Acc) ->
      {Filter, Acc}.
  
  is_field_nullable(FieldName, ?DDL{fields = Fields}) when is_binary(FieldName)->
      #riak_field_v1{optional = Optional} = lists:keyfind(FieldName, #riak_field_v1.name, Fields),
  