SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 2)
   ExpressionList (children 1)
    Function materialize (alias m) (children 1)
     ExpressionList (children 1)
      Function map (children 1)
       ExpressionList (children 4)
        Literal \'foo\'
        Literal UInt64_1
        Literal \'bar\'
        Literal UInt64_2
   ExpressionList (children 2)
    Identifier m.keys
    Identifier m.values
