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Allows Sequel to reuse an ActiveRecord connection
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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.

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 fairly advanced Sequel usage.


Add this line to your application's Gemfile:

gem "sequel-activerecord_connection"

And then execute:

$ bundle install

Or install it yourself as:

$ gem install sequel-activerecord_connection


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(test: false) # avoid creating a connection
DB.extension :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

  title: "Sequel::ActiveRecordConnection",
  body:  "Allows Sequel to reuse ActiveRecord's connection",
#=> 1

#=> [{ 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(test: false) # for "postgresql" adapter
# or
DB = Sequel.mysql2(test: false) # for "mysql2" adapter
# or
DB = Sequel.sqlite(test: false) # for "sqlite3" adapter


The database extension overrides Sequel transactions to use ActiveRecord transcations, which allows using ActiveRecord inside Sequel transactions (and vice-versa), and have things like ActiveRecord's transactional callbacks still work correctly.

DB.transaction do
  ActiveRecord::Base.transaction do
    # this all works

The following Sequel transaction options are currently supported:

  • :savepoint
  • :auto_savepoint
  • :rollback
ActiveRecord::Base.transaction do
  DB.transaction(savepoint: true) do # will create a savepoint
    DB.transaction do # will not create a savepoint
      # ...

The #in_transaction? method is supported as well:

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

Other transaction-related Sequel methods (#after_commit, #after_rollback etc) are not supported, because ActiveRecord currently doesn't provide transactional callbacks on the connection level (only on the model level).


To ensure Sequel compatibility, any ActiveRecord::StatementInvalid exceptions will be translated into Sequel exceptions:

DB[:posts].multi_insert [{ id: 1 }, { id: 1 }]
#~> Sequel::UniqueConstraintViolation

DB[:posts].insert(title: nil)
#~> Sequel::NotNullConstraintViolation

DB[:posts].insert(author_id: 123)
#~> Sequel::ForeignKeyConstraintViolation


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 }
DB.activerecord_model = MyModel


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


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


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

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