After updating to Redmine 3.3 we began to encounter broken issue trees quite often. Root and parent ids are ok, but lft and rgt values get messed up somehow. We have ~250k issues so using @Issue.rebuild_tree!@ is a rather expensive task with enormous overhead as 99.99% of nested sets are ok and it is usually one or two that get broken from time to time.

I suppose having a possibility to rebuild only a single nested set would be very useful in such situations. Below is the code I'm using to do so now - just added it to /lib/redmine/nested_set/issue_nested_set.rb

def rebuild_single_tree!(root_id)
  root = Issue.find(root_id)
  if root.blank? || !root.parent_id.blank?
    p "Wrong root specified"
    return
  end
  transaction do           
    where(root_id: root_id).update_all(:lft => nil, :rgt => nil)
    where(root_id: root_id, parent_id: nil).update_all(["lft = ?, rgt = ?", 1, 2])
    rebuild_nodes(root_id)    
  end
end