Example of using UUIDs for primary keys in ActiveRecord

example.rb

require 'active_record'
ActiveRecord::Base.establish_connection adapter: 'postgresql', database: 'josh_test'
ActiveRecord::Schema.define do
  self.verbose = false
  enable_extension 'pgcrypto'
  create_table :conversations, id: :uuid do |t|
    t.string :topic
  end
  create_table :messages, id: :uuid do |t|
    t.uuid :conversation_id, null: false, index: true
    t.string :body
  end
end

class Conversation < ActiveRecord::Base
  has_many :messages
end

class Message < ActiveRecord::Base
  belongs_to :conversation
end

Conversation.create! messages: [Message.new(body: 'hello'), Message.new(body: 'world')]
pp Message.first.conversation.messages.order(body: :asc).to_a