Re: Efficient XPath 2.0 expression to return each <row

If this is a real task support effort and not just a learning exercise and you're using Oxygen then I would follow Graydon's lead and use XQuery 3 to build a map that can then give you a quick answer.

  for $row in /airports/row
  group by $id := $row/navaid
  where $row[2]
  return $row