PgLtree

Gem that allows use ltree in ActiveRecord models.

It uses a implementation based around PostgreSQL's ltree data type, associated functions and operators.

Author	Andrei Panamarenka
Version	1.1.7 (March 20, 2018)
License	Released under the MIT license.

Support

• Ruby 2.*
• Rails >= 4, < 5.3
• Pg adapter (gem 'pg') >= 0.17, < 2

Installation

Add this line to your application's Gemfile:

gem 'pg_ltree', '1.1.7'

And then execute:

$ bundle

Add ltree extension to PostgreSQL:

class AddLtreeExtension < ActiveRecord::Migration
  def change
    enable_extension 'ltree'
  end
end

Update your model:

class AnyModel < ActiveRecord::Migration
  def change
    add_column :any_model, :path, :ltree

    add_index :any_model, :path, using: :gist
  end
end

Run migrations:

$ bundle exec rake db:migrate

Usage

  class AnyModel < ActiveRecord::Base
    ltree :path
    # ltree :path, cascade: false # Disable cascade update and delete
  end

  root     = AnyModel.create!(path: 'Top')
  child    = AnyModel.create!(path: 'Top.Science')
  subchild = AnyModel.create!(path: 'Top.Science.Astronomy')

  root.parent   # => nil
  child.parent # => root
  root.children # => [child]
  root.children.first.children.first # => subchild
  subchild.root # => root

For find a lots of additional information about PgLtee see:

• Wiki
• List of methods for work with LTree
• Module SCOPE FOR (For not uniq path in tree)