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Comment by moe | Hacker News Reader

What is it with these mainstay frameworks that they never adopt the mature ORM on their respective platform but instead keep growing their own, less than half-baked alternative?

We have this in django vs SQLAlchemy and Rails vs datamapper.

The arguments that I've heard were mostly that the respective ORMs either weren't around when the framework started and/or that anyone "can just plug their preferred ORM in anyways". Neither really cuts it for me. Even in java-land (yes, java!) they make more sense in that regard - everyone just uses hibernate.

Well, however other than this unrelated rant (triggered by the mention of the removal of a most basic ORM-wart...); Good work django guys. :-)

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I love SQLAlchemy - it's an amazing piece of software, and I use it often. So why wouldn't I argue for Django to switch?

* I love Django's ORM, too. It's far simpler, much easier to teach to new users, and results in code that "scans" better. It's only able to achieve that ease-of-use by sacrificing features -- a classic trade-off. Neither approach is more "right."

* SQLAlchemy didn't exist when we wrote Django. Yes, you've just dismissed that argument, but I can't. There are thousands -- probably tens of thousands -- of Django sites out there, and I'm not so quick to break backwards compatibility just for the new shiny.

* Finally, and most importantly, SQLAlchemy has some fundamentally different goals than Django's ORM. SQLAlchemy aims to provide an API to represent SQL in Python. Django aims to provide a persistance layer for objects. The difference between these philosophies is important: the use of a relational database is almost an implementation detail for Django, but it's SQLAlchemy's raison d'être. This isn't just academic: it means, for example, that Django's ORM will one day support non-relational databases (work here's already begun), but SQLAlchemy won't.

Your last point is by far the most important. It looks like one of the goals for Django 1.4 will be more separation between the ORM and relational databases. Alex Gaynor speaks at length about the innards of today's querysets and how he suggests it could be changed to make sense with NoSQL: http://nosql.mypopescu.com/post/904840384/django-and-nosql-d...

Wow, actually had an article starred on this in the trusty Reader. http://jmoiron.net/blog/about-sqlalchemy-and-djangos-orm/

Money quote for me: "SQLAlchemy is a toolkit for python programmers who want or need to use a database to write programs that do so. Django's ORM is a tool for python programmers to quickly model business-level data relationships and use a database for persistent storage. This is really an important distinction; the Django ORM interface is focused on the application's data model, whereas SQLAlchemy's interface is focused on the underlying data store."

I feel that Django's ORM is one the main reasons for its success. Yes, it's limited and simplistic compared to something like Hibernate -- but that's actually a blessing in this context. People love Django because it makes it so simple to build an application quickly. Without the built-in ORM, things like admin and generic views would be harder to implement and certainly wouldn't work anywhere nearly as nicely out of the box.

Django's ORM existed before SQLAlchemy, and ActiveRecord existed before DataMapper.

Wasn't one of the major reasons for the giant Rails 3 switchover to allow datamapper or other ORM's to be used in place of activerecord?

Don't know about the Rails world so much. But Django's "loose coupling" allows you to use a different ORM if you see fit as well. Though that's to be dosed with salt to taste... you lose some fun automagic stuff like manage.py <load/dump>data, contrib.admin, sessions

A quick stackexchange search yielded a link here http://lethain.com/entry/2008/jul/23/replacing-django-s-orm-...

It's not so much that they couldn't be used before, but the coupling was so tight that there was a high burden on the maintainers to fix things when they broke.

With the creation of a stable internal API for all of these kinds of things, DataMapper can now be just as much of a first class citizen as ActiveRecord.

I love Django's ORM.

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