Help: cant get count for has_many :through

Rails
1

I have 3 tables, that provide a restful mechanism for creating history
for products. There is a list of (almost static) states that are linked
to a product via a progressions table.

eg states
1 ordered
2 processed
3 sent

PROBLEM
Im interested in getting the release list for a given state, eg
State.find_by_name(‘ordered’).products

When i progress a product to processed, that product will still appear
in the ordered list. At the moment i am doing the following, its rather
clumsy:

@processed_products = State.find_by_name('processed').products
@ordered_products = State.find_by_name('ordered').products -
@processed_products

This works fine, but now i need to get a count for the tabs (like in
google), and running all those selects seems over kill and SLOW. Ive
been looking at creating a query on the progression object using a
combination of order and distinct, or perhaps an association extension.

But just cant work it out…

TABLES
states
id
name

products
id
name
etc

progressions
id
state_id
product_id
created_by
created_at

2

Im thinking the only way around this is to add a column closed_at

then set this in a before_save model callback

then create an association extension called current the adds the
condition. closed_at = nil.

Any thoughts?