[Gordonjcp]

> in fact RDBMSes are highly optimized pieces of software that are especially good at combining sets of data. Much better than ORMs, anyway,

ORMs are just a wrapper around RDBMSes. If your ORM is producing incredibly stupid SQL to query the DB with, you might want to check that you're not modelling your data in a stupid way.

I am by no means an expert, but in general I have found that if the ORM is doing something particularly crazy, it's because my underlying assumptions about the data model is wrong.