The Complexity of Active Record Transactions

I’ve recently picked up the sequel-activerecord_connection gem again to make some reliability improvements around database transactions. For context, this gem extends Sequel with the ability to reuse Active Record’s database connection, which should lower the barrier for trying out Sequel in apps that use Active Record.After pushing some fixes, I was thinking how working on this gem has greatly increased my familiarity with the internals of database transaction implementations of both Active Record and Sequel. Since there aren’t any existing articles on this topic, I thought it would be useful to share the knowledge I gathered over the past few months.