1. Create your migration

create_table :nodes do |t|
  t.text :name
  t.integer :parent_id
  t.references :parent
end
add_index :nodes, [:parent_id, :id], :unique => true

2. Create your model

class Node < ActiveRecord::Base
include Treeify
tree_config({:cols => [:name]})

validates_uniqueness_of :name
validates_uniqueness_of :parent_id, :scope=> :id
end

3. Create a tree of stuff

parent = Node.create(name: "parent node")

parent.children << Node.new(name: "child 1")

parent.children.first.children << Node.new(name: "child 2")

4. Retrieve tree of stuff

parent.descendent_tree

# which should give you something like this:
[
  {
    "id"=>168,
    "name"=>"child 1",
    "parent_id"=>167,
    "children"=>
      [
        {
          "id"=>169, 
          "name"=>"child 2", 
          "parent_id"=>168, 
          "children"=>[]
        }
      ]
  }
]

The SQL Generated looks something like this:

 SELECT "nodes".* FROM "nodes"  WHERE (nodes.id IN (WITH RECURSIVE cte (id, path)  AS (
       SELECT  id,
         array[id] AS path
       FROM    nodes
       WHERE   id = 8

       UNION ALL

       SELECT  nodes.id,
          cte.path || posts.id
       FROM    nodes
       JOIN cte ON nodes.parent_id = cte.id
     )
     SELECT id FROM cte
     ORDER BY path))  ORDER BY posts.id

I haven't done much in terms of benchmarking, but it seems like using a join would be better than using an IN() clause here. I'm looking to improve this in future versions.

In the spirit of keeping things simple, Treeify does just a few things:

1. Provides a has_many :children relationship which is a self-join that allows you to collect the direct descendents of any node.
2. On the flip side, it provides a belongs_to :parent relationship to get a node's parent, if one exists
3. The roots scope, which retrieves all parent records (their parent_id is null)
4. tree_config Allows you to pass in custom column names to be retrieved. THIS ~~~WILL~~~ HAS CHANGED as "config" isn't nearly generic enough to not cause conflicts with other libraries.
5. descendents Retrieves direct descendents of a node
6. descendent_tree Returns an array of hashes containing a tree-like structure of a given node's descendents and sub-descendents.

This all started off as a fork of acts_as_sane_tree, until I discovered it would be an enormous pain to port it directly over to be rails 4 compatible. I read through a few things, and decided it would be best just to huck some SQL into a few methods and shape the data as needed. For now, it works fine.

As I've stated before, I want to optimize the SQL and clean up the code to be less repetitive, and get some actual benchmarks going.

I'm not using the other gems that provide tree like retrieval because I don't agree so much with nested sets, adjacency lists, and while materialized paths aren't awful, Postgres provides functionality that performs much better.

The MIT License (MIT)

Copyright (c) 2015 Devin Joel Austin

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

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