A UUID PROTOTYPE

This is a prototype which use uuid datatype with postgresql and rails 4.1.9.

What is uuid datatype and why we use this?

"A UUID is an identifier that is unique across both space and time, with respect to the space of all UUIDs. Since a UUID is a fixed size and contains a time field, it is possible for values to rollover (around A.D. 3400, depending on the specific algorithm used)."

"Unless you're accepting IDs on, say, an Internet-wide scale, or with an untrusted environment where malicious individuals might be able to do something bad in the case of an ID collision, it's just not something you should worry about."

Installation

rails new proto_uuid_app

And change database in Gemfile

gem "pg"

Run

bundle install

How to use uuid type

rails g migration enable_uuid_extension

class EnableUuidExtension < ActiveRecord::Migration
  def change
    enable_extension 'uuid-ossp'
  end
end

Use uuid type with your model

rails g model user

class CreateUsers < ActiveRecord::Migration
  def change
    create_table :users, id: :uuid do |t|
      t.string :name
      t.timestamps
    end
  end
end

Now, you can create a user with auto-generated id as a UUID type.

UUID as a different field

If you want to use uuid as an extra field

class AddUuidToUsers < ActiveRecord::Migration
  def change
    add_column :users, :uuid, :uuid, default: 'uuid_generate_v4()'
  end
end

Add another model and relate to user model

rails g model course

class CreateCourses < ActiveRecord::Migration
  def change
    create_table :courses, id: :uuid do |t|
      t.string :name
      t.uuid :user_id
      t.timestamps
    end
  end
end

Be sure that, user_id field of course is uuid type because a user's id is also uuid type.

Also, you want to look at:

• http://www.postgresql.org/docs/9.4/static/uuid-ossp.html
• http://andrzejonsoftware.blogspot.com.tr/2013/12/decentralise-id-generation.html
• https://github.com/rails/rails/blob/master/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb#L338-L342
• http://en.wikipedia.org/wiki/Universally_unique_identifier#Random%5FUUID%5Fprobability%5Fof%5Fduplicates