Updating several records at once in rails

Have you tried using update_all ?

http://api.rubyonrails.org/classes/ActiveRecord/Relation.html#method-i-update_all

It sounds like you are looking for ActiveRecord::Base.update_all - from the documentation:

Updates all records with details given if they match a set of conditions supplied, limits and order can also be supplied. This method constructs a single SQL UPDATE statement and sends it straight to the database. It does not instantiate the involved models and it does not trigger Active Record callbacks or validations.

Product.last_day_of_freshness.update_all(:stale => true)

Actually, since this is rails 2.x (You didn't specify) - the named_scope chaining may not work, you might need to pass the conditions for your named scope as the second parameter to update_all instead of chaining it onto the end of the Product scope.