The other day I had to display the number of children items an object had so I decided to do the following:
@customers = Customer.find(:all, :include=>[:receive_payments])
<%= customer.receive_payments.count %>
While this worked for what I needed, it executed the following sql every iteration:
SELECT count(*) AS count_all FROM "receive_payments" WHERE ("receive_payments".customer_ref_list_id = E'850000-1071531366')
I thought this wasn’t right considering I used an association, however when you use count, it forces the use of count(*) on the database. This is where size comes in!!!!
<%= customer.receive_payments.size %>
Now we get the same results without the extra database counts!