rails generate migration enable_pgcrypto_extension

enable_pgcrypto_extension.rb

# enable_pgcrypto_extension.rb
class EnablePgcryptoExtension < ActiveRecord::Migration[5.1]
  def change
    enable_extension 'pgcrypto'
  end
end

# config/application.rb
config.generators do |g|
  g.orm :active_record, primary_key_type: :uuid
end

# 20160918103122_create_users.rb
class CreatePosts < ActiveRecord::Migration[5.1]
  def change
    create_table :posts, id: :uuid do |t|
      t.string :title

      t.timestamps
    end
  end
end

add_column :posts, :id, default: "uuid_generate_v4()", null: false

class EnablePgcryptoExtension < ActiveRecord::Migration[5.1]
  def change
    enable_extension 'uuid-ossp'
    enable_extension 'pgcrypto'
  end
end