*******************************************************
  * This is very experimental code, and has not been    *
  * tested on a wide range of databases.                *
  *                                                     *
  * Please exercise caution!                            *
  *                                                     *
  * Patches and suggestions for improvement may be      *
  * submitted to the mailing list on rubyforge.         *
  *******************************************************

= acts_as_materialized_tree

Allows you to create a model which forms a "materialized tree", that is, one
where each node contains an explicit path. This allows for efficient subtree
searches [expensive in acts_as_tree] and insertion and removal of children
[expensive in acts_as_nested_set]

Requires ActiveRecord 2.1.x or later.

=== Example

In your model:

  class Foo < ActiveRecord::Base
    acts_as_materialized_tree
  end

  a = Foo.find(1)
  p a.children.count                     # count done via SQL
  p a.descendants.find(:name=>'brian')   # search in subtree only

In your migration:

  create_table :foos do |t|
    t.string   :path,       :null => false, :default => ""
    t.integer  :next_child, :null => false, :default => 0
  end
  add_index :foos, :path, :unique => true

See ActiveRecord::Acts::MaterializedTree::ClassMethods and
ActiveRecord::Acts::MaterializedTree::InstanceMethods for more information.

Copyright (C) 2008 Brian Candler <B.Candler@pobox.com>. Released under the
MIT licence.