Reducing N+1 queries by eager loading

I read through the documentation and couldn't find a built-in solution to this problem. When certain models are serialized we need to make sure that the query to retrieve that entity always adds an includes to avoid all the lazy loaded N+1 queries. We can do this via records as long as the request is on the resources controller. If it's not then I couldn't see a place to extend it.

Let me give an example

class ProjectResource
  has_one :company
end

class CompanyResource
  attribute :plan_start_at

  def plan_start_at
    @model.subscription.created_at
  end
end

As you'll notice each time a company is rendered it is going to retrieve a value out of it's subscription. However, the problem comes in when we request a URL like this

/api/projects?include=company

It's using the records method off of the projects resource and even when it goes to process the include on company it's not calling records on the company resource so we end up with a separate query for every companies subscription.

Now, from what I can tell maybe this is supposed to be taken care of by also requesting the subscription like this

/api/projects?include=company,company.subscription

However this doesn't completely work since I don't need the subscription object and requesting the subscription isn't a concern of the client (since we simply need the subscription in order to calculate a property on the company.)

Start by tracing the resources controller, the records method, and the include processing described for ProjectResource and CompanyResource. Reproduce the /api/projects?include=company case and compare it with company.subscription; done means dependent data used by computed attributes is eager loaded without requiring clients to request that relationship.