Eager loading of polymorphic associations in ActiveRecord

Question

This is my first time using Rails and I was wondering if it\'s possible to load a has one polymorphic association in one SQL query? The models and associations between them are

Answer 1

After digging through the Rails source I've discovered that you can force a join by referencing a table other than the current model in either the select, conditions or order clauses.

So, if I specify an order on the Asset table:

Image.first(
      :conditions => {:id => id},
      :include => :asset,
      :order => "asset.id"
)

The resulting SQL will use a left outer join and everything in one statement. I would have preferred an inner join, but I guess this will do for now.