Deleting old user sessions from Rails database

purge_old_sessions.rb

# app/modes/session.rb
class Session < ActiveRecord::Base
  named_scope :unactive_for, lambda{|period| {:conditions => ['sessions.updated_at <= ?', Time.now - period]}}

  def self.purge_older_than period
    unactive_for(period).find_in_batches do |sessions|
      sessions.each{|s| "#{s.id}: s.destroy"}
    end
  end
end

# Rakefile
desc "Will delete user sessions unactive for specified period as DAYS. Which defaults to 14."
task :purge_old_sessions => [:environment] do
  days = if days = ENV['DAYS']
             days.to_i
           else
             14
           end

  puts "Deleting user sessions last updated more than #{days} days ago. #{Session.unactive_for(days.days).count} in total."
  Session.purge_older_than(days.days)
  puts "Complete"
end