SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 1)
   ExpressionList (children 1)
    Function CAST (children 1)
     ExpressionList (children 2)
      Function tuple (children 1)
       ExpressionList (children 2)
        Literal \'a\'
        Function array (children 1)
         ExpressionList (children 1)
          Function map (children 1)
           ExpressionList (children 2)
            Literal \'b\'
            Literal \'42\'
      Literal \'Tuple(String, Array(Map(String, Variant(UInt32, FixedString(1000000)))))\'
