new_nds = (nds - old_nodes).sort.uniq
unless new_nds.empty?
- db_nds = Node.where(:id => new_nds, :visible => true)
+ # NOTE: nodes are locked here to ensure they can't be deleted before
+ # the current transaction commits.
+ db_nds = Node.where(:id => new_nds, :visible => true).lock("for share")
if db_nds.length < new_nds.length
missing = new_nds - db_nds.collect(&:id)