TypedUUID

A Typed UUID is an UUID with an enum embeded within the UUID.

UUIDs are 128bit or 16bytes. The hex format is represented below where x is a hex representation of 4 bits.

xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx

Where:

• M is 4 bits and is the Version
• N is 3 bits and is the Variant of the Version followed a bit

We modify this and use the following structure where the 7th & 8th bytes in the UUID are enum XORed with the result of XORing bytes 5 & 6 with bytes 9 & 10.

xxxxxxxx-YYYY-TTTT-ZZZZ-xxxxxxxxxxxx

Where:

• TTTT is the Type ENUM 0bNNNN_NNNN_NNNN_NNNN (0 - 65,535) XORed with (YYYY xor ZZZZ)
• YYYY bytes XORed with ZZZZ and the Type ENUM to produce the identifying bytes
• ZZZZ bytes XORed with YYYY and the Type ENUM to produce the identifying bytes

XORing bytes 5 & 6 with 9 & 10 and XORing again with bytes 5 & 6 of the Typed UUID will give us back the ENUM of the Type using soley the UUID.

Install

Add this to your Gemfile:

gem 'typed_uuid'

Once bundled you can add an initializer to Rails to register your types as shown below. This maps the table_names of the models to an integer between 0 and 255.

# config/initializers/uuid_types.rb

ActiveRecord::Base.register_uuid_types({
  listings:     0,
  buildings:    65_535
})

# Or:

ActiveRecord::Base.register_uuid_types({
  0         => :listings,
  65_535    => :buildings
})

Usage

In your migrations simply replace id: :uuid with id: :typed_uuid when creating a table.

class CreateProperties < ActiveRecord::Migration[5.2]
  def change    
    create_table :properties, id: :typed_uuid do |t|
      t.string "name", limit: 255
    end
  end
end