Question

I have a User model in which

default_scope :order => 'created at desc'

I currently have fifty records, ids 1 through 50.

User.first returns User id: 50.

User.first(2) returns User id: 50 and User id: 49

User.last returns User id: 1

This all makes sense. However,

User.last(2) returns User id: 49 and User id: 50, in that order. Why is that? And how do I return User id: 1 and User id: 2?

Answer 1

This is a common mistake. User.last(1) and User.last() are not exactly same. User.last(1) would give you an array of a single record while User.last() would return that record object.

Again, both these methods would behave entirely differently if you have a default_scope in your User model.

User.last just works on your default scope, reversing its order. So the SQL query it fires is:

SELECT * FROM users ORDER BY created_at ASC LIMIT 1

On the other hand, User.last(1) is similar to writing User.order('id desc').limit(1). And with your default_scope in action, the order by id desc would come second to the default one. So the SQL it fires would be:

SELECT * FROM users ORDER BY created_at desc, id desc LIMIT 1

So what you really need to do here is remove the default scope using User.unscoped as Kien has mentioned.
Personally, I avoid using default scope ordering and use explicit scoping instead.