ruby on rails manys' many

Question

I am wondering how to do this without double each loop. Assume that I have a user model and order model, and user has_many orders.

Now I have a users array which class is User::ActiveRecord_Relation

How can I get the orders of these users in one line?

Answer 1

Actually, the best way to do that is :

users.includes(:orders).map(&:orders)

Cause you eager load the orders of the users (only 2 sql queries)

Or

Order.where(user_id: users.pluck(:id))

is quite good too in term of performance