Eager loading polymorphic associations

after.rb

class Picture < ApplicationRecord
  belongs_to :employee , -> { left_joins(:picture).merge(Picture.of_employee) }, foreign_key: :imageable_id, inverse_of: :pictures
  belongs_to :product , -> { left_joins(:product).merge(Picture.of_product) }, foreign_key: :imageable_id, inverse_of: :pictures
  scope :of_employee, -> { where(imageable_type: "Employee") }
  scope :of_product, -> { where(imegeable_type: "Product") }
end

class Employee < ApplicationRecord
  has_many :pictures, -> { of_employee }, dependent: nil, foreign_key: :imageable_id, inverse_of: :employee
end

class Product < ApplicationRecord
  has_many :pictures, -> { of_product }, dependent: nil, foreign_key: :imageable_id, inverse_of: :product
end

before.rb

class Picture < ApplicationRecord
  belongs_to :imageable, polymorphic: true
end

class Employee < ApplicationRecord
  has_many :pictures, as: :imageable
end

class Product < ApplicationRecord
  has_many :pictures, as: :imageable
end