ActiveRecordUuid

active_record_uuid is a nice gem that add uuid supports to your activerecord models (MySQL). It allows you to store uuid in various formats: binary (16 bytes), base64 (24 bytes), hexdigest (32 bytes), or string (36 bytes), and query back with uuid string.

The performance issues arises when you store primary key in large data size. You have two options:

use auto-increment primary key along with uuid column
use uuid primary key, but store in binary format

You have various choices when storing uuid:

binary format, 16 bytes
base64 format, 24 bytes (encode uuid into base64)
hexdigest, 32 bytes string (compact uuid format, without dash)
string, 36 bytes string (full length uuid)

Check this out for more detail, http://www.mysqlperformanceblog.com/2007/03/13/to-uuid-or-not-to-uuid/.

Installation

Add this line to your application's Gemfile:

gem 'active_record_uuid'

And then execute:

$ bundle

Or install it yourself as:

$ gem install active_record_uuid

Upgrade from version 0.0.1

ActiveRecordBase::UuidBase and UuidBaseHelper are depreciated. Right now, you can configure your model by using has_uuid and inherit from ActiveRecord::Base. Check out the usage below.

Upgrade from version 0.1.0

uuid_config is fine, but I like to use has_uuid and passing in options instead.

Usage

If you need to use uuid column as primary key, don't add any :primary_key in migration file, because it will make that column as auto-increment integer primary key. Instead, do something like this:

create_table :posts, :force => true, :id => false do |t|
  t.string :uuid, :limit => 36
  t.string :text
  t.timestamps
end

$ rake db:add_primary_keys            # Add primary keys to all models
$ rake db:add_primary_key[model_name] # Add primary key to a model

Migration

In order for the gem to work well, you need to specify the column type and limit correctly according to your has_uuid (store_as option).

create_table :posts, :force => true, :id => false do |t|
  t.binary :uuid, :limit => 16 # `must set to the correct value`
  t.string :text
  t.timestamps
end

class Post < ActiveRecord::Base
  has_uuid :primary_key => true, :store_as => :binary
end

General configuration options

You can configure using ActiveRecordUuid.configure, and it will apply to any models which use has_uuid. Each model can overwrite the general options by passing options into has_uuid. The following are default values:

ActiveRecordUuid.configure do
  column      :uuid           # :uuid is default
  primary_key true            # false is default
  association false           # false is default
  generator   :timestamp      # :timestamp is default
  store_as    :string         # :string is default
  hook        :before_create  # :before_validation is default
end

There's a config generator that generates the default configuration file into config/initializers directory. Run the following generator command, then edit the generated file.

$ rails g active_record_uuid:config

Model configuration

To use uuid in your model, call has_uuid in your model.

class Post < ActiveRecord::Base
  has_uuid :primary_key => true, :hook => :before_create
end

# create a post with auto-generated uuid
post = Post.new(:text => "Manual uuid")
post.save
post.uuid   # "79f8a42e-ae60-11e1-9aa9-0026b90faf3c"

# create a post with manual uuid
post = Post.new(:text => "Manual uuid")
post.uuid = "79f8a42e-ae60-11e1-9aa9-0026b90faf3c"
post.save

# assign a uuid
post.assign_uuid

# assign a uuid and save immediately
post.assign_uuid!

# check the uuid value is valid or not
post.uuid_valid?

# generate a new uuid
Post.generate_uuid

Binary uuid model (example)

class PostBinary < ActiveRecord::Base
  has_uuid :primary_key => true, :store_as => :binary
end

post = PostBinary.create(:text => "Binary uuid1")
# INSERT INTO `post_binaries` (`created_at`, `text`, `updated_at`, `uuid`) VALUES ('2012-06-20 17:32:47', 'Binary uuid1', '2012-06-20 17:32:47', x'4748f690bac311e18e440026b90faf3c')

post.uuid # "4748f690-bac3-11e1-8e44-0026b90faf3c"

# it works as usual for finding records
PostBinary.find_by_uuid(post.uuid)
PostBinary.where(:uuid => post.uuid)
PostBinary.find(post)
PostBinary.find(post.uuid)
PostBinary.find([post.uuid])
post.comments.create(:text => "Comment 1")

# access the value that stored in db
post.reload
post.attributes_before_type_cast["uuid"]["value"]

Avaliable options inside `has_uuid`

`column` option

Set the column name to store uuid value.

`primary_key` option

Specify whether the value of column is primary key or not.

`generator` option

Specify which generator amongs [:random, :timestamp] used to generate uuid value.

`store_as` option

Specify which format to store. Possible values are [:binary, :base64, :hexdigest, :string].

`hook` option

Specify the activerecord hook [:after_initialize, :before_validation, :before_create] to generate uuid value. Assign it to :after_intialize when you want to associate this record to its children.

`assoication` option

When you set this option to true, it expects you have foreign_keys with _uuid. Therefore, you don't have to pass :foreign_key option inside association methods

class Author < ActiveRecord::Base
  has_uuid :primary_key => true, :association => true
  has_and_belongs_to_many :posts
end

class Post < ActiveRecord::Base
  has_uuid :primary_key => true, :association => true
  has_many :comments
  has_one  :comment
  has_and_belongs_to_many :authors
end

class Comment < ActiveRecord::Base
  has_uuid :primary_key => true, :association => true
  belongs_to :post
end

# overwrite :foreign_key option and add additional option
class Post < ActiveRecord::Base
  has_uuid :primary_key => true, :association => true
  has_many :comments, :foreign_key => "comment_id", :inverse_of => :post
end

Testing

This gem will set the format for dumping the database schema to :sql. This means that it is no longer dump the schema to ruby code but database-independent version, db/structure.sql. Therefore, you would not have any problems when running the tests.