eager load polymorphic rails
You need to add a custom belongs_to to your polymorphic model
class Shipment
  has_many :payments, as: :paymentable
end
class Payment  
  belongs_to :paymentable, polymorphic: true
  # Add a custom belongs_to that points to Shipment
  belongs_to :shipment, foreign_type: 'Shipment', foreign_key: 'paymentable_id'
end
