Rails: includes with polymorphic association

Question

I read this interesting article about Using Polymorphism to Make a Better Activity Feed in Rails.

We end up with something like

class Activity < A         


        

Answer 1

Does this generate a valid SQL query or does it fail because events can't be JOINed with tags and images can't be JOINed with guests?

class Activity < ActiveRecord::Base
  self.per_page = 10

  def self.feed
    includes(subject: [:guests, :tags]).order(created_at: :desc)
  end
end

# in the controller

Activity.feed.paginate(page: params[:page])

This would use will_paginate.