Eager load differently nested polymorphic

Question

Using Rails 3.2. My models are nested in such a way:

• Review => Reviewable (Country or Shop)
• Country => CountryDay => Shop => Photos
• Shop => Photo

Answer 1

I think I had the same problem just now. I got an ActiveRecord::EagerLoadPolymorphicError when trying to load associations. My solution was to put together a custom join statement which I've put into a scope for easier usage.

Untested, but this may get you going:

class Review < ActiveRecord::Base
  scope :eagerly_loaded, -> {
    joins('
      INNER JOIN shops 
      ON (reviews.reviewable_type = "Shop" AND reviews.reviewable_id = shops.id)
      INNER JOIN countries 
      ON (reviews.reviewable_type = "Country" reviews.reviewable_id = countries.id)
    ')
  }
end

You then use @user.reviews.eagerly_loaded. Make sure to use a matching .group()-statement to only get the ones you need.