SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 1)
   ExpressionList (children 1)
    Function in (children 1)
     ExpressionList (children 2)
      Literal UInt64_1
      Subquery (children 1)
       SelectWithUnionQuery (children 1)
        ExpressionList (children 1)
         SelectQuery (children 1)
          ExpressionList (children 1)
           Function file (children 1)
            ExpressionList (children 1)
             Function materialize (children 1)
              ExpressionList (children 1)
               Literal \'a\'
