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 UInt64_42
      Literal \'Tuple(String, Array(Map(String, Variant(LowCardinality(UInt64), String))))\'
