On the new query interface in Rails 3

There’s no doubt that the new query interface in Rails 3 is nice for simple queries. For example:

new_users = User.order('users.id DESC').limit(20).includes(:items)

Reads a lot more nicely than:

new_users = User.all :order => 'users.id DESC', :limit => 20, :include => :items

But I really don’t see it as a compelling alternative for complex queries. For these, nothing will ever beat dropping down to raw SQL.

Take an example from this weblog post by the mastermind of the new query system. He argues that this:

photo_counts = photos.
project(photos[:user_id], photos[:id].count)

Followed by this:


Is better than this:

SELECT users.*, photos_aggregation.cnt
FROM users
LEFT OUTER JOIN (SELECT user_id, count(*) as cnt FROM photos GROUP BY user_id) AS photos_aggregation
ON photos_aggregation.user_id = users.id

I’m afraid I just can’t agree with that. For me, when complex joins and subqueries are involved, the mental gymnastics required to convert the actual operations on the database (which are described with a perfect one-to-one correspondence by the SQL syntax) into the rather arcane, abstract Ruby equivalent, just aren’t worth the effort, and I can’t see how they ever will be.