Code review comment for lp:~cedric-lebrouster/ocb-server/ocb-7.0-bug-1253052-parent-order

This patch looks a bit scary at first, mainly because you have to read it closely to convince yourself that it doesn't trigger a recomputation on every write().

#123-133 can be done in one SQL statement I think, given that we touch that code anyway such an optimization wouldn't hurt imho.