Rails destroy all but newest n records

Question

How do I destroy all but the newest n records using Rails\' ActiveRecord?

I can get the newest n records using order and limit but how do I destroy the inverse?

Answer 1

Previous answers use find or last require the creation of ActiveModel, which take extra computation time.

I think using pluck is better, since it only creates an Array of ids.

ids = Foo.limit(n).order('id DESC').pluck(:id)
Foo.where('id NOT IN (?)', ids).destroy_all