Dear Drools users,

I'm new to Drools but loving it so far. I have a question about accumulate and window:lengt:

What I want: "Display the average order value considering the last 200 orders for one type of product. I want have at least 10 orders for one product before drawing any conclusions"

How I solved it now, it's not working as I want it:

I now insert product objects to be able to group the orders per product. The first problem is that the list of products is not unique but every insert creates a new product object (even though the product object has already been inserted for that productId), so the second rule is triggered way too often. I don't actually want to insert this product object, but I don't know how else to group on product otherwise. Any help on this part is greatly appreciated.

The second problem is that the window doesn't seem to use all the orders matching the product, it just limits the rule to use the last 200 orders, not the last 200 orders for that product. Is there a way to make this smarter?

(I can't share our source code, so this might not compile)

declare Product

    productId : String;

end

delcare Order

    @role(event)

    productId: String;

    price: int;

end

rule "Turn purchase into order"

when

    p : Purchase()

then

    insert ( new Product(p.productId) )

    insert ( new Order(p.productId, p.price)

rule "Count average price"

when

    $product : Product ()

    accumulate(

        Order(productId == $product.productId, $pr : price ) over window:length(200);

        $avg : average( $pr ),

        $count: count($pr);

        $count > 10, $avg < 10)

then

    "The average price for product $product.productId is $avg"