Storing an order object in a cookie based session


I have a simple e-commerce store and am running into a problem with the
edge rails cookie based sessions.

What I am trying to do is make the customer fill in their info, and
click “Review my Order”. The order object is contructed, and stored in
the session (if it passes validation). The is sent to another page
where they can confirm all their info and press the “finalize order”

The problem is that the order object is too large to fit in the session,
and I get a CGI::Session::CookieStore::CookieOverflow exception. The
addresses and other customer data overflow the 4k limit.

So, without switching session stores, whats the best way to fix this? I
don’t really want to store the order object in the session, but it
seemed like the easiest option.

I thought about only storing the posted params from the order form, but
that seems messy and doesn’t save much in the way data size. I thought
about saving the order to the database, but that seems wrong since the
customer has not actually agreed to place the order yet.

This is more or less what I am trying to do:

def review
session[:order] =[:order])

def finalize

How can I do this without “abusing” the session by storing ActiveRecord
object in it?