A drop in replacement for acts_as_tree with super fast ancestors and subtree access
Ruby
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README.rdoc

acts_as_tree_with_dotted_ids

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

Example:

root
 \_ child1
      \_ subchild1
      \_ subchild2

Usage:

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"

Improvements

The plugin adds the following instance methods:

  • ancestor_of?(node)

  • self_and_ancestors

  • descendant_of?(node)

  • all_children

  • depth

The following methods of have been rewritten to take advantage of the dotted IDs:

  • root

  • ancestors

  • siblings

  • self_and_sibblings

Migration

If you already have an acts_as_tree model, you can easily upgrade it to take advantage of the dotted IDs.

  1. 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.

  2. Call MyTreeModel.rebuild_dotted_ids! and you are ready to go.

Compatibility

From version 1.2.0, this gem is only compatible with Rails 4.x and up.

Thanks

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