Consider the following polymorphic relationship:
class Comment
belongs_to :commentable, polymorphic: true
end
class User
has_many :posts
has_many :groups
end
class Group
belongs_to :user
has_many :comments, as: :commentable
end
class Post
belongs_to :user
has_many :comments, as: :commentable
end
Essentially a user has post comments and group comments. I want to return user total comments. One way of achieving this is:
posts = @user.posts.map {|c| c.comments}.flatten
groups = @user.groups.map {|c| c.comments}.flatten
However, this is database intensive. It is possible to eager load here like this:
Comment.includes(:commentable).where(commentable: {user_id: self.id})
# ActiveRecord::EagerLoadPolymorphicError: Cannot eagerly load the polymorphic association :commentable
