This is an extension to Rails good old acts_as_tree which uses an extra “dotted_ids” column which stores the path of the node as a string of record IDs joined by dots, hence the name.
This optimization solves performance issues related to in-database tree structure by allowing for direct O(1) ancestor/child verification and O(N) subtree access with one single query.
class Category < ActiveRecord::Base acts_as_tree_with_dotted_ids :order => "name" end
root \_ child1 \_ subchild1 \_ subchild2
root = Category.create("name" => "root") child1 = root.children.create("name" => "child1") subchild1 = child1.children.create("name" => "subchild1") root.parent # => nil child1.parent # => root root.children # => [child1] root.children.first.children.first # => subchild1 child1.ancestors_of?(subchild2) # => true subchild1.descendant_of?(root) # => true root.id # 1 child1.id # 2 subchild1.id # 3 root.dotted_ids # "1" child1.dotted_ids # "1.2" subchild1.dotted_ids # "1.2.3"
The plugin adds the following instance methods:
The following methods of have been rewritten to take advantage of the dotted IDs:
If you already have an acts_as_tree model, you can easily upgrade it to take advantage of the dotted IDs.
Just add the dotted_ids column to your table. In most case a string should be enough (it's also better for the indexing) but if your tree is very deep you may want to use a text column.
Call MyTreeModel.rebuild_dotted_ids! and you are ready to go.
Tested with Rails 2.x and MySQL 5.x as well as SQLite.
Gem packaging and Rails 3 compatibility by Thomas Maurer – github.com/tma
Kudos to all the contributors to the original plugin.
Copyright © 2007 David Heinemeier Hansson, released under the MIT license
Copyright © 2008 Xavier Defrang, released under the MIT license