Sequel::ActiveRecordConnection

This is an extension for Sequel that allows it to reuse an existing ActiveRecord connection for database interaction. It works on ActiveRecord 4.2 or higher, and supports the built-in postgresql, mysql2 and sqlite3 adapters, as well as JDBC adapter for JRuby.

This can be useful if you're using a library that uses Sequel for database interaction (e.g. Rodauth), but you want to avoid creating a separate database connection. Or if you're transitioning from ActiveRecord to Sequel, and want the database connection to be shared.

Note that this is a best-effort implementation, so some discrepancies are still possible. That being said, this implementation passes Rodauth's test suite (for all adapters), which has some fairly advanced Sequel usage.

Installation

Add this line to your application's Gemfile:

gem "sequel-activerecord_connection", "~> 0.3"

And then execute:

$ bundle install

Or install it yourself as:

$ gem install sequel-activerecord_connection

Usage

Assuming you've configured your ActiveRecord connection, you can initialize the appropriate Sequel adapter and load the activerecord_connection extension:

require "sequel"

DB = Sequel.postgres(extensions: :activerecord_connection)

Now any Sequel operations that you make will internaly be done using the ActiveRecord connection, so you should see the queries in your ActiveRecord logs.

DB.create_table :posts do
  primary_key :id
  String :title, null: false
  Stirng :body, null: false
end

DB[:posts].insert(
  title: "Sequel::ActiveRecordConnection",
  body:  "Allows Sequel to reuse ActiveRecord's connection",
)
#=> 1

DB[:posts].all
#=> [{ title: "Sequel::ActiveRecordConnection", body: "Allows Sequel to reuse ActiveRecord's connection" }]

DB[:posts].update(title: "sequel-activerecord_connection")
#=> 1

The database extension supports postgresql, mysql2 and sqlite3 ActiveRecord adapters, just make sure to initialize the corresponding Sequel adapter before loading the extension.

DB = Sequel.postgres(extensions: :activerecord_connection) # for "postgresql" adapter
# or
DB = Sequel.mysql2(extensions: :activerecord_connection) # for "mysql2" adapter
# or
DB = Sequel.sqlite(extensions: :activerecord_connection) # for "sqlite3" adapter
# or
DB = Sequel.jdbc(extensions: :activerecord_connection) # for JDBC adapter

Transactions

This database extension keeps the transaction state of Sequel and ActiveRecord in sync, allowing you to use Sequel and ActiveRecord transactions interchangeably (including nesting them), and have things like ActiveRecord's and Sequel's transactional callbacks still work correctly.

ActiveRecord::Base.transaction do
  DB.in_transaction? #=> true
end

Sequel's transaction API is fully supported:

DB.transaction(isolation: :serializable) do
  DB.after_commit { ... } # executed after transaction commits
  DB.transaction(savepoint: true) do # creates a savepoint
    DB.after_commit(savepoint: true) { ... } # executed if all enclosing savepoints have been released
  end
end

One caveat to keep in mind is that using Sequel's transaction/savepoint hooks currently don't work if ActiveRecord holds the corresponding transaction/savepoint. This is because it's difficult to be notified when ActiveRecord commits or rolls back the transaction/savepoint.

DB.transaction do
  DB.after_commit { ... } # will get executed
end

DB.transaction do
  DB.transaction(savepoint: true) do
    DB.after_commit(savepoint: true) { ... } # will get executed
  end
end

ActiveRecord::Base.transaction do
  DB.after_commit { ... } # not allowed (will raise Sequel::ActiveRecordConnection::Error)
end

DB.transaction do
  ActiveRecord::Base.transaction(requires_new: true) do
    DB.after_commit(savepoint: true) { ... } # not allowed (will raise Sequel::ActiveRecordConnection::Error)
  end
end

Model

By default, the connection configuration will be read from ActiveRecord::Base. If you want to use connection configuration from a different model, you can can assign it to the database object after loading the extension:

class MyModel < ActiveRecord::Base
  connects_to database: { writing: :animals, reading: :animals_replica }
end

DB.activerecord_model = MyModel

Timezone

Sequel's database timezone will be automatically set to ActiveRecord's default timezone (:utc by default) when the extension is loaded.

If you happen to be changing ActiveRecord's default timezone after you've loaded the extension, make sure to reflect that in your Sequel database object, for example:

DB.timezone = :local

Tests

You'll first want to run the rake tasks for setting up databases and users:

$ rake db_setup_postgres
$ rake db_setup_mysql

Then you can run the tests:

$ rake test

When you're done, you can delete the created databases and users:

$ rake db_teardown_postgres
$ rake db_teardown_mysql

License

The gem is available as open source under the terms of the MIT License.

Code of Conduct

Everyone interacting in this project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.