# File lib/ancestry/class_methods.rb, line 163
    def rebuild_depth_cache!
      raise Ancestry::AncestryException.new("Cannot rebuild depth cache for model without depth caching.") unless respond_to? :depth_cache_column
      
      self.base_class.send(:with_exclusive_scope) do 
        self.base_class.find_each do |node|
          node.update_attribute depth_cache_column, node.depth
        end
      end
    end