Not that I have your attention! I've been having a discussion with a
respected colleague here:
http://phpbuilder.com/board/showthread.php?t=10340411 (Rails vs. PHP)
He's basically saying that Rails won't be able to scale because
referential integrity and tranactions are done in the application rather
than the database. Please read the referenced thread for much more info.
Transactions are handled by the db.
And RoR doesn't prevent you from doing RI in the db. However, you
kindof need it in the app layer as well, for simple error handling and
so on, which certainly adds some overhead. Yay for mysql..
My main grief from a scalability pov is lack of support for prepared
statements / bind variables. That's 30-80% more load on your db, which
is the hardest layer to scale out.
However, i think it's being worked on..