desc "Clean up Active Record sessions updated before ENV['EXPIRE_AT'] (defaults to 3 weeks ago)."
  task :clean_ar_sessions => :environment do 
    time = ENV['EXPIRE_AT'] || 3.weeks.ago.to_s(:db)
    rows = CGI::Session::ActiveRecordStore::Session.delete_all ["updated_at < ?", time]
    RAILS_DEFAULT_LOGGER.info "#{rows} session row(s) deleted."
  end