sequel-activerecord_connection
This is a database extension for Sequel that makes it to reuse an existing Active Record connection for database interaction.
This can be useful if you want to use a library that uses Sequel (e.g. Rodauth or rom-sql), or you're transitioning from Active Record to Sequel, or if you just want to use Sequel for more complex queries, and you want to avoid creating new database connections.
It works on ActiveRecord 4.2+ and fully supports PostgresSQL, MySQL and SQLite,
both the native adapters and JDBC (JRuby). The SQL Server external adapter is
supported as well (tinytds
in Sequel), and there is attempted support for
Oracle enhanced (oracle
and in Sequel). Other adapters might work too, but
their integration hasn't been tested.
Why reuse the database connection?
At first it might appear that, as long as you're fine with the performance impact of your database server having to maintain additional open connections, it would be fine if Sequel had its own database connection. However, there are additional caveats when you try to combine it with Active Record.
If Sequel and Active Record each have their own connections, then it's not possible to combine their transactions. If we executed a Sequel query inside of an Active Record transaction, that query won't actually be executed inside a database transaction. This is because transactions are tied to the database connection; if one connection opens a transaction, this doesn't affect queries executed on a different connection, even if both connections are used in the same ruby process. With this library, transactions and queries can be seamlessly combined between Active Record and Sequel.
In Rails context, there are additional considerations for a Sequel connection
to play nicely. Connecting and disconnecting would have to go in lockstep with
Active Record, to make commands such as rails db:create
and rails db:drop
work. You'd also need to find a way for system tests and the app running in the
background to share the same database connection, which is something Sequel
wasn't designed for. Reusing Active Record's connection means (dis)connecting
and sharing between threads is all handled automatically.
Framework Agnostic
The only hard dependencies are:
...which means you can use it with any Rack / Ruby based framework: Rails / Roda / Sinatra etc. or even without a framework.
Installation
Add the gem to your project:
$ bundle add sequel-activerecord_connection
Usage
Assuming you've configured your ActiveRecord connection, you can initialize the
appropriate Sequel adapter and load the activerecord_connection
extension: e.g.
# Place in relevant initializer
# e.g. Rails: config/initializers/sequel.rb
require "sequel"
DB = Sequel.postgres(extensions: :activerecord_connection) # postgres
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.
Sequel.postgres(extensions: :activerecord_connection) # for "postgresql" adapter
Sequel.mysql2(extensions: :activerecord_connection) # for "mysql2" adapter
Sequel.sqlite(extensions: :activerecord_connection) # for "sqlite3" adapter
If you're on JRuby, you should be using the JDBC adapters:
Sequel.connect("jdbc:postgresql://", extensions: :activerecord_connection) # for "jdbcpostgresql" adapter
Sequel.connect("jdbc:mysql://", extensions: :activerecord_connection) # for "jdbcmysql" adapter
Sequel.connect("jdbc:sqlite://", extensions: :activerecord_connection) # for "jdbcsqlite3" 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
When registering transaction hooks, they will be registered on Sequel transactions when possible, in which case they will behave as described in the Sequel docs.
# Sequel: An after_commit transaction hook will always get executed if the outer
# transaction commits, even if it's added inside a savepoint that's rolled back.
DB.transaction do
ActiveRecord::Base.transaction(requires_new: true) do
DB.after_commit { puts "after commit" }
raise ActiveRecord::Rollback
end
end
#>> BEGIN
#>> SAVEPOINT active_record_1
#>> ROLLBACK TO SAVEPOINT active_record_1
#>> COMMIT
#>> after commit
# Sequel: An after_commit savepoint hook will get executed only after the outer
# transaction commits, given that all enclosing savepoints have been released.
DB.transaction(auto_savepoint: true) do
DB.transaction do
DB.after_commit(savepoint: true) { puts "after commit" }
raise Sequel::Rollback
end
end
#>> BEGIN
#>> SAVEPOINT active_record_1
#>> ROLLBACK TO SAVEPOINT active_record_1
#>> COMMIT
In case of (a) adding a transaction hook while Active Record holds the transaction, or (b) adding a savepoint hook when Active Record holds any enclosing savepoint, Active Record transaction callbacks will be used instead of Sequel hooks, which have slightly different behaviour in some circumstances.
# ActiveRecord: An after_commit transaction callback is not executed if any
# if the enclosing savepoints have been rolled back
ActiveRecord::Base.transaction do
DB.transaction(savepoint: true) do
DB.after_commit { puts "after commit" }
raise Sequel::Rollback
end
end
#>> BEGIN
#>> SAVEPOINT active_record_1
#>> ROLLBACK TO SAVEPOINT active_record_1
#>> COMMIT
# ActiveRecord: An after_commit transaction callback can be executed already
# after a savepoint is released, if the enclosing transaction is not joinable.
ActiveRecord::Base.transaction(joinable: false) do
DB.transaction do
DB.after_commit { puts "after savepoint release" }
end
end
#>> BEGIN
#>> SAVEPOINT active_record_1
#>> RELEASE SAVEPOINT active_record_1
#>> after savepoint release
#>> COMMIT
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
Normalizing SQL logs
Active Record injects values into queries using bound variables, and displays them at the end of SQL logs:
SELECT accounts.* FROM accounts WHERE accounts.email = $1 LIMIT $2 [["email", "[email protected]"], ["LIMIT", 1]]
Sequel interpolates values into its queries, so by default its SQL logs include them inline:
SELECT accounts.* FROM accounts WHERE accounts.email = '[email protected]' LIMIT 1
If you want to normalize logs to group similar queries, or you want to protect sensitive data from being stored in the logs, you can use the sql_log_normalizer extension to remove literal strings and numbers from logged SQL queries:
Sequel.postgres(extensions: [:activerecord_connection, :sql_log_normalizer])
SELECT accounts.* FROM accounts WHERE accounts.email = ? LIMIT ?
Note that the sql_log_normalizer
extension opens a database connection while
it's being loaded. If you're setting up Sequel in a Rails initializer, you'll
probably want to handle the database not existing, so that commands such as
rails db:create
continue to work.
DB = Sequel.postgres(extensions: :activerecord_connection)
begin
DB.extension :sql_log_normalizer
rescue ActiveRecord::NoDatabaseError
end
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
Support
Please feel free to raise a new disucssion in Github issues, or search amongst the existing questions there.
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.