Active Record, the sludge in Ruby

So I've been learning Ruby lately, and being a bug ORM guy I decided to checkout the source for active record and see how it works. There are some very serious issues here. Active record uses the dynamic mixin ability of Ruby to do its work, but that same logic kills itself in performance. To explain myself further I we should compare the active record model with JPA.

JPA
Java persistence architecture delegates all ORM work to the persistence manager, an external library that manages db entities. If I want an entity I ask the persistence manager for it, if I want to save, I do it through the persistence manager. When my app starts up the persistence manager looks at all my entities and my schema and creates the necessary object structure to do its ORM magic. The mapping/querying logic is done once and used by everyone.

ActiveRecord
Active record delegates all ORM work to the entity itself. Entities must know how to query/save themselves and if they are transient or persistent. They do this by mixing in methods to to the ruby-defined entities at runtime and then, when an instance of an entity is instantiated, created the necessary links to do its ORM stuff.

The disadvantage of active record is the function of ORM processes is spread throughout however many entities you have. It becomes hard to do things like locking, transactional caching and even transactional enlistment. If I have a 100 entities, each entity has to be concerned with cache invalidation and managing their relationships.


Until the ruby community either fixes this in active record, or comes out with a JPA/Hibernate -like ORM they will never be in the spotlight. If you talk to any ruby-evangelist they always bring up that Twitter uses RoR. And that is true, but if you read any of their posts to scale Twitter had to remove ActiveRecord from their deployment because it was just too slow.

So I think Ruby is cool but I really don't like active record. Anyone interested in porting hibernate to Ruby???