SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 1)
   ExpressionList (children 1)
    Function arraySort (children 1)
     ExpressionList (children 1)
      Function arrayUnion (children 1)
       ExpressionList (children 3)
        Literal Array_[NULL, NULL, NULL, UInt64_1]
        Literal Array_[UInt64_1, NULL, NULL]
        Literal Array_[UInt64_1, UInt64_2, UInt64_3, NULL]