This gem provides the railtie that allows sequel to hook into Rails (5.2.x, 6.x, 7.x, 8.x) and thus behave like a rails framework component. Just like activerecord does in rails, sequel-rails uses the railtie API to hook into rails. The two are actually hooked into rails almost identically.

The code for this gem was initially taken from the excellent dm-rails project.

This was originally a fork of brasten's sequel-rails that has been updated to support newer versions of rails.

Since January 2013, we've become the official maintainers of the gem after brasten proposed us.

Using sequel with Rails (5.2.x, 6.x, 7.x, 8.x) requires a few minor changes.

First, add the following to your Gemfile (after the Rails lines):

# depending on you database
gem "pg"        # for PostgreSQL
gem "mysql2"    # for MySQL
gem "sqlite3"   # for Sqlite

gem "sequel-rails"

... be sure to run "bundle install" if needed!

Secondly, you'll need to require the different Rails components separately in your config/application.rb file, and not require ActiveRecord. The top of your config/application.rb will probably look something like:

# require 'rails/all'

# Instead of 'rails/all', require these:
%w(
  action_cable/engine
  action_controller/railtie
  action_mailer/railtie
  action_view/railtie
  active_job/railtie
  rails/test_unit/railtie
).each do |railtie|
  begin
    require railtie
  rescue LoadError
  end
end

Then you need to get rid of ActiveRecord and ActiveStorage configurations, that is if you didn't generate the new app with -O (or the long form --skip-active-record):

For example in a fresh Rails 7, you would need to remove those lines:

config/environments/development.rb
line 37:  # config.active_storage.service = :local
line 54:  # config.active_record.migration_error = :page_load
line 57:  # config.active_record.verbose_query_logs = true

config/environments/production.rb
line 41:  # config.active_storage.service = :local
line 92:  # config.active_record.dump_schema_after_migration = false

Starting with sequel-rails 0.4.0.pre3 we don't change default Sequel behaviour nor include any plugin by default, if you want to get back the previous behaviour, you can create a new initializer (eg: config/initializers/sequel.rb) with content:

require "sequel_rails/railties/legacy_model_config"

Rake db:* mappings are currently not supported in Rails 7, so you'll need to use the sequel:* tasks instead. For example, to migrate your database, you'll need to run rails sequel:migrate instead of rails db:migrate.

The rake command to create your db requires that Sequel does not attempt to connect to load models before creating the db. Add this to your config/application.rb

# config/application.rb
if defined?(Rake.application)  && Rake.application.top_level_tasks.include?('sequel:create')
  config.sequel.skip_connect = true
end

After those changes, you should be good to go!

1. Connection management:

   sequel-rails will initiate the Sequel connection mechanism based on your configuration in database.yml.

2. Generators:

   You can use them just like ActiveRecord's ones:

   Migration:

   rails generate migration create_admin_users
   # Or
   rails generate migration CreateAdminUsers

   Model:

   rails generate model User email:string

   Observer:

   rails generate observer User

   Session:

   rails generate sequel:session_migration

3. Rake tasks similar to ActiveRecord, see Available sequel specific rake tasks

4. Add some Sequel and sequel-rails specific exceptions to ActionDispatch's rescue_responses

   Sequel::Plugins::RailsExtensions::ModelNotFound is mapped to :not_found

   Sequel::NoMatchingRow is mapped to :not_found

   Sequel::ValidationFailed is mapped to :unprocessable_entity

   Sequel::NoExistingObject is mapped to :unprocessable_entity

5. Add a i18n_scope method to Sequel::Model which respond with "sequel". This is used by ActiveModel.

6. Adding Sequel to ActiveSupport::LogSubscriber. This is what allows you to see SQL queries in the log and also allows us to implement the next item.

7. Add a hook in ActionController::Base so that the sum of SQL queries time for the current action is reported as DB for the controller's line in logs.

8. Provide a ActionDispatch::Session::SequelStore similar to the ActiveRecord one, which stores sessions in database backed by a Sequel model.

You can configure some options with the usual rails mechanism, in config/application.rb and/or in config/environments/*.rb.

    # Allowed options: :sql, :ruby.
    config.sequel.schema_format = :sql

    # Allowed options: true, false, default false
    config.sequel.allow_missing_migration_files = true

    # Whether to dump the schema after successful migrations.
    # Defaults to false in production and test, true otherwise.
    config.sequel.schema_dump = true

    # These override corresponding settings from the database config.
    config.sequel.max_connections = 16
    config.sequel.search_path = %w(mine public)

    # Configure whether database's rake tasks will be loaded or not.
    #
    # If passed a String or Symbol, this will replace the `db:` namespace for
    # the database's Rake tasks.
    #
    # ex: config.sequel.load_database_tasks = :sequel
    #     will results in `rake db:migrate` to become `rake sequel:migrate`
    #
    # Defaults to true
    config.sequel.load_database_tasks = false

    # This setting disabled the automatic connect after Rails init
    config.sequel.skip_connect = true

    # Configure if Sequel should try to 'test' the database connection in order
    # to fail early
    config.sequel.test_connect = true

    # Configure what should happend after SequelRails will create new connection with Sequel (applicable only for the first new connection)
    # config.sequel.after_connect = proc do
    #   Sequel::Model.plugin :timestamps, update_on_create: true
    #   Sequel::Model.db.extension :pg_array, :pg_hstore # database specific extension
    #   Sequel.extension :pg_hstore_ops # sequel specific extension
    # end

    # Configure what should happend after new connection in connection pool is created (applicable only for all connections)
    # to fail early
    # config.sequel.after_new_connection = proc do |db|
    #   db.execute('SET statement_timeout = 30000;')
    # end

    # If you want to use a specific logger
    config.sequel.logger = MyLogger.new($stdout)

The connection settings are read from the file config/database.yml and is expected to be similar to ActiveRecord's format.

Here's some examples:

1. For PostgreSQL:

   development:
     adapter: postgresql
     database: a_database_name
     user: user_name # Also accept 'username' as key, if both are present 'username' is used
     password: password
     host: 10.0.0.2 # Optional
     port: 5432 # Optional
     owner: owner_name # Optional
     encoding: utf8 # Optional, also accept 'charset' as key, if both are present 'encoding' is used (defaults to 'utf8')
     maintenance_db: template2 # Optional
     locale: en_US.UTF-8 # Optional, equivalent to setting 'collation' and 'ctype' to the same value
     collation: en_US.UTF-8 # Optional
     ctype: en_US.UTF-8 # Optional
     template: template1 # Optional
     tablespace: non_default_tablespace_name # Optional
     max_connections: 20 # Optional, also accept 'pool' as key, if both are present 'max_connections' is used (default to nil, Sequel default is 4)
     url: "postgres://myuser:mypass@host/somedatabase" # Optional, if present it's passed to `Sequel.connect` with other config as options
                                                       # If url is not set in config file, environment variable `DATABASE_URL` is used

2. For MySQL:

   development:
     adapter: mysql # Also accept mysql2
     database: a_database_name
     user: user_name # Also accept 'username' as key, if both are present 'username' is used
     password: password
     host: 10.0.0.2 # Optional
     port: 5432 # Optional
     charset: latin1 # Optional (defaults to 'utf8')
     collation: latin1_general_ci # Optional (defaults to 'utf8_unicode_ci')
     url: "mysql://myuser:mypass@host/somedatabase" # Optional, if present it's passed to `Sequel.connect` with other config as options
                                                    # If url is not set in config file, environment variable `DATABASE_URL` is used

3. For SQLite:

   development:
     adapter: sqlite # Also accept sqlite3
     database: db/mydatabase.sqlite # Path to db relative to Rails root

For in memory testing:

     development:
      adapter: sqlite # Also accept sqlite3
      database: ":memory:"

There are 2 options how to set after_connect hooks in config/application.rb

1. config.sequel.after_connect will be called only on the first new connection. It can be used for enabling plugins or to set some global sequel settings.

  config.sequel.after_connect = proc do
    Sequel::Model.plugin :timestamps, update_on_create: true
    Sequel::Model.db.extension :pg_array, :pg_hstore # database specific extension
    Sequel.extension :pg_hstore_ops # sequel specific extension
  end

2. config.sequel.after_new_connection will be called after every new connection in connection pool is created. It can be used to run some specific SET commands on every new connection. It's using default after_connect hook in sequel. https://sequel.jeremyevans.net/rdoc/classes/Sequel/ConnectionPool.html#attribute-i-after_connect

 config.sequel.after_new_connection = proc do |db|
   db.execute('SET statement_timeout = 30000;')
 end

If you want to enable plugins for all your models, you should use the after_connect configuration option in config/application.rb (0.6.2+):

    config.sequel.after_connect = proc do
      Sequel::Model.plugin :timestamps, update_on_create: true
    end

This will ensure that these plugins are loaded before any Sequel models are loaded. Loading plugins into Sequel::Model after subclasses are already created is not supported by Sequel. You can also load extensions in after_connect or perform any custom actions that you need.

Please note: some plugins require a dataset to work, which means they can't be added via Sequel::Model.plugin, they need to be added to a Sequel::Model subclass whose underlying table exists.

If you want to store your session in the database you can use the provided session store backed by a Sequel model. Edit your config/initializers/session.rb file and replace the existing code with:

YourAppName::Application.config.session_store :sequel_store

You can then generate a migration for the session table using the provided generator:

rails generate sequel:session_migration
rake db:migrate

Optionally if you want to use your own Sequel model to handle the session, you can do so in your config/initializers/session.rb:

ActionDispatch::Session::SequelStore.session_class = MyCustomSessionModelClass

To get a list of all available rake tasks in your rails3 app, issue the usual in you app's root directory:

rake -T

or if you don't have hooks in place to run commands with bundle by default:

bundle exec rake -T

Once you do that, you will see the following rake tasks among others. These are the ones that sequel-rails added or replaced:

rake db:create[env]                   # Create the database defined in config/database.yml for the current Rails.env
rake db:create:all                    # Create all the local databases defined in config/database.yml
rake db:drop[env]                     # Drop the database defined in config/database.yml for the current Rails.env
rake db:drop:all                      # Drops all the local databases defined in config/database.yml
rake db:force_close_open_connections  # Forcibly close any open connections to the test database
rake db:migrate                       # Migrate the database to the latest version
rake db:migrate:down                  # Runs the "down" for a given migration VERSION.
rake db:migrate:redo                  # Rollbacks the database one migration and re migrate up.
rake db:migrate:reset                 # Resets your database using your migrations for the current environment
rake db:migrate:up                    # Runs the "up" for a given migration VERSION.
rake db:reset                         # Drops and recreates the database from db/schema.rb for the current environment and loads the seeds.
rake db:schema:dump                   # Create a db/schema.rb file that can be portably used against any DB supported by Sequel
rake db:schema:load                   # Load a schema.rb file into the database
rake db:seed                          # Load the seed data from db/seeds.rb
rake db:setup                         # Create the database, load the schema, and initialize with the seed data
rake db:test:prepare                  # Prepare test database (ensure all migrations ran, drop and re-create database then load schema). This task can be run in the same invocation as other task (eg: rake db:migrate db:test:prepare).
rake db:sessions:clear                # Delete all sessions from the database
rake db:sessions:trim[threshold]      # Delete all sessions older than `threshold` days (default to 30 days, eg: rake db:session:trim[10])

• Fork the project.
• Make your feature addition or bug fix.
• Add specs for it. This is important so I don't break it in a future version unintentionally.
• Commit, do not mess with rakefile, version, or history. (if you want to have your own version, that is fine but bump version in a commit by itself I can ignore when I pull)
• Send me a pull request. Bonus points for topic branches.

• Jonathan Tron (@JonathanTron) - Current maintainer
• Joseph Halter (@JosephHalter) - Current maintainer

Original project:

• Brasten Sager (@brasten) - Project creator

Improvements have been made by those awesome contributors:

• Benjamin Atkin (@benatkin)
• Gabor Ratky (@rgabo)
• Joshua Hansen (@binarypaladin)
• Arron Washington (@radicaled)
• Thiago Pradi (@tchandy)
• Sascha Cunz (@scunz)
• Brian Donovan (@eventualbuddha)
• Jack Danger Canty (@JackDanger)
• Ed Ruder (@edruder)
• Rafał Rzepecki (@dividedmind)
• Sean Sorrell (@rudle)
• Saulius Grigaliunas (@sauliusg)
• Jacques Crocker (@railsjedi)
• Eric Strathmeyer (@strathmeyer)
• Jan Berdajs (@mrbrdo)
• Robert Payne (@robertjpayne)
• Kevin Menard (@nirvdrum)
• Chris Heisterkamp (@cheister)
• Tamir Duberstein (@tamird)
• shelling (@shelling)
• a3gis (@a3gis)
• Andrey Chernih (@andreychernih)
• Nico Rieck (@gix)
• Alexander Birkner (@BirknerAlex)
• kr3ssh (@kressh)
• John Anderson (@djellemah)
• Larivact (@Larivact)
• Jan Berdajs (@mrbrdo)
• Lukas Fittl (@lfittl)
• Jordan Owens (@jkowens)
• Pablo Herrero (@pabloh)
• Henre Botha (@henrebotha)
• Mohammad Satrio (@tyok)
• Gencer W. Genç (@gencer)
• Steve Hoeksema (@steveh)
• Jester (@Jesterovskiy)
• ckoenig (@ckoenig)
• Rolf Timmermans (@rolftimmermans)
• Olivier Lacan (@olivierlacan)
• Dustin Byrne (@dsbyrne)
• Michael Coyne (@mjc-gh)
• p-leger (@p-leger)
• Semyon Pupkov (@artofhuman)
• Ben Koshy (@BKSpurgeon)
• Janko Marohnić (@janko)
• Adrián Mugnolo (@xymbol)
• Ivan (@AnotherRegularDude)
• kamilpavlicko (@kamilpavlicko)
• Stefan Vermaas (@stefanvermaas)
• Yuri Smirnov (@tycooon)
• Mickael Kurmann (@elbouillon)
• Radoslaw Wojnarowski (@rwojnarowski)
• David Kelly (@opensourceame)
• PikachuEXE (@PikachuEXE)

The dm-rails team wrote most of the original code, I just sequel-ized it, but since then most of it has been either adapted or rewritten.

Copyright (c) 2010-2022 The sequel-rails team. See LICENSE for details.