SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 1)
   ExpressionList (children 2)
    Function materialize (alias x) (children 1)
     ExpressionList (children 1)
      Function array (children 1)
       ExpressionList (children 1)
        Function toNullable (children 1)
         ExpressionList (children 1)
          Literal UInt64_1
    Function arrayElement (alias y) (children 1)
     ExpressionList (children 2)
      Identifier x
      Function toNullable (children 1)
       ExpressionList (children 1)
        Literal UInt64_1
