eager loading and polymorphic associations

There is a dedicated section about eager loading in the docs. A coworker discovered eager loading does not work in polymorphic associations the hard way :slight_smile: so I've written a patch that documents it:


There are at least a couple of tickets that implement something that would change that though:


What do you think?

-- fxn

Committed. Thanks Xavier!

#9640 will be dipping its toes into trunk soon too.