scopes.rb

scope :approved_for_slideshow,  ->{
  includes(:promo).
  where('promos.show_in_slideshow is not false').
  where('approved_for_slideshow_at is not null')
}


----- vs -----
  
scope :approved_for_slideshow,  ->{
  where('approved_for_slideshow_at is not null')
}

scope :including_slideshow_promos,  ->{
  includes(:promo).
  where('promos.show_in_slideshow is not false')
}