anchor.diff:          end, [], Filter1),
       lists:keystore(filter, 1, WhereProps, {filter,Filter2}).
   
  -check_where_clause_is_possible_fold(DDL, _Conditional, {'=',{field,FieldName,_},{const,?SQL_NULL}} = F, Acc) ->
  +check_where_clause_is_possible_fold(DDL, _, {'=',{field,FieldName,_},{const,?SQL_NULL}} = F, Acc) ->
       %% `IS NULL` filters
       %% if a column is marked NOT NULL, but the WHERE clause has IS NULL for that
       %% column then no results will ever be returned, so do not execute!
  
positive.code:         false ->
              {eliminate, Acc}
      end;
  check_where_clause_is_possible_fold(_, _, Filter, Acc) ->
      {Filter, Acc}.
  
  
negative.code:         S?SQL_SELECT.'WHERE'
      ).
  
  is_null_clause_on_non_null_column_is_impossible_test() ->
      DDL = get_ddl(
          "CREATE TABLE table1("
  