anchor.diff:    int _rowsAffected;
     
     List<String> _columnNames;
  -  Map<String, int> _columnIndex;
  +  Map<Symbol, int> _columnIndex;
     
     _Query(this.sql);
     
  
positive.code:     
      _columnNames = _columns.map((c) => c.name).toList();
      
      _columnIndex = new Map<String, int>();
      for (var i = 0; i < _columnNames.length; i++) {
        _columnIndex[_columnNames[i]] = i;
      }
    }
    
  
negative.code:   }
    
    // Map column name to column index
    final Map<Symbol, int> _index;
    final List<String> _columnNames;
    final List _columnValues;
    
  