FWIW In a recent project managed to circumvent this problem by
querying and pre-fetching all child items before starting the outer
loop(s). (I hope there's a simpler way!)
As I recall it would mean your code would look something like this:
(untested)
# Coax DM into preloading collections:
customers = Customer.all(:limit => 3)
customers.orders.reload
customers.orders.order_lines.reload
#For items you may need to prepare something like:
item_ids = customers.orders.lines.map{|l| l.item_id }
items = Item.all( :id => item_ids )
# Then try your original loops with a slight tweak for item.sku:
customers.each do |c|
c.orders.each do |o|
o.order_lines.each do |ol|
a = "#{c.name}: #{o.reference} #{ol.quantity} x
#{ items.first(:id => ol.item_id).sku }"
end
end
end
Food for thought anyway. Hopefully a more DM-savvy reader can improve
on this.
George
On Sep 30, 8:24 am, Marcel Hild <[email protected]> wrote:
> Hi,
> I recreated the model found
> athttp://datamapper.org/docs/find#nested_conditions
> When I want to print out all Customers with all Orders, including
> OrderLines and everything,
> Datamapper eager loads the first association (Customer.orders) but for
> the rest
> it will issue n queries.
>
> I created a gist which shows it athttp://gist.github.com/604156
>
> Is there a way to have more control of what is loaded or should I fire
> the query differently?
>
> thanks for any input
>
> marcel
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