UUID primary keys in Rails 3

Gemfile

# Gemfile
…
gem 'uuidtools' 
…

migrations.rb

# db/migrate/20110422210841_create_sites.rb
# 1.  :id => false
# 2.  :uuid 
#
class CreateSites < ActiveRecord::Migration
  def self.up
    create_table(:sites, :id => false) do |t|
      t.string :uuid, :limit => 36, :primary => true
      t.timestamps
    end
  end

  def self.down
    drop_table :sites
  end
end

site.rb

# app/models/site.rb
class Site < ActiveRecord::Base
  include Extensions::UUID
end

uuid.rb

# app/models/extensions/uuid.rb
#
module Extensions
  module UUID
    extend ActiveSupport::Concern

    included do
      # old rails versions 
      set_primary_key 'uuid'
      # later rails versions, untested:
      # self.primary_key = 'the_name'

      before_create :generate_uuid
      
      def generate_uuid
        self.id = UUIDTools::UUID.random_create.to_s
      end
    end
  end
end

This isn't the best idea to let rails handle the UUID's. Race conditions are possible and collisions are possible. It's probably best to let MySQL or Postgres handle it via the built in function UUID(). I'm going to do a write up about it soon and how to accomplish UUID's with rails.

I was using this approach for a long time, but now after upgrading it stops working. I also get

Got this when i did run some spec:
DEPRECATION WARNING: Calling set_primary_key is deprecated. Please use self.primary_key = 'the_name' instead.

and morover i get new error

uninitialized constant RSpec::Matchers::Extensions::UUID

in rspec tests when trying to use routing paths, which used to work.

Is there a update to this approach? (hopefully not radically different]

@warmwaffles you should probably read more about UUIDs and primary key uniqueness ;-)

When possible and you don't mind the database lock-in, do it in the database.

Sometimes, when you have an async API that pushes customer data e.g. on a MQ/redis. You need to generate and return the UUID on the customer-facing system. You can't wait/block for the full, async database round-trip.

If you are using Ruby 1.9.3+ you can just call SecureRandom.uuid. You also don't need gem 'uuidtools'.

Thanks for this.

For Rails 3.1+ check ActiveUUID