The best way to combine two active record queries

Question

What difference between two approaches shown below and what is better:

        user.photos & Photo.public

and

        user.photos.where('photos.id IN (?)', Photo.public.select(:id))

Is there better way to combine two active record queries ?

Answer 1

The first will be using an array join, the second is doing two queries, neither is as efficient as adding another scope to your Photo model:

 # Photo Model
  scope :public, where {:public => true }
  scope :user, lambda { |user| where("user_id = ?", user) }

  # Controller
  Photo.public.user(user)

Answer 2

Given that Photo#public is a scope, ex.:

scope :public, -> { where(:public => true) }

You can simply write

user.photos.public

Answer 3

如果您不能使用新范围，我建议您：

user.photos.merge(Photo.public)