so you are using drools to build on-the-fly queries based on user input. You could probably do this via "static" rules. Since you basically have 4 variables (price, avg_user_rating, num_ratings, category), you could write 4 rules, one each that filters based on one of the 4 variables and then chain the execution through salience:

rule price:
salience 1
when
        $p: Product(price in param)
then
        add $p to result

rule avg_user_rating:
salience 2
when
        $p: Product(avg_user_rating > param)
then
        add $p to result


and so on




From:        soumya_sd <soumya_sd@yahoo.com>
To:        rules-users@lists.jboss.org,
Date:        05/09/2012 08:43 AM
Subject:        Re: [rules-users] Is there a faster way of doing this in Drools ?
Sent by:        rules-users-bounces@lists.jboss.org

---

Vincent Legendre wrote
>
> Users changing rules IS the correct use-case of drools (I would even say
> that if rules never change, drools is likely to be worse than pure java).
> What others said is "changing the rules at each request by regenerating
> and recompiling" is not.
>
> I can't imagine that users may change rules at each request, so you must
> have, at least for some time (thus a lot of requests), a stable rule base.
> What is costly is to compile rules, but you already know that.
> So the idea is to keep in some kind of cache the actual rules, and only
> recompile them when they change.
>
> The source of rules does not matter : you can generate the DRL according
> to your configuration, or make you users directly write rules (with
> guvnor, which will fits well if your rules are only basic filters).
>
> The optimisation you have to do is to keep your compiled rules somewhere
> (by serializing your KnowlegdePackages or simply keep it in a kind of
> map), and reuse it until your source change : you have to find a way to
> detect that rules (or the config that is used to generate them) have
> changed, and then recompile a new up-to-date KnowledgePackage.
>
>

Thank you for your insights.

At this point I'm designing for the worst case i.e., I'm assuming the rules
with change with every request.

Moreover, this can happen on a regular basis in the system I'm trying to
design.

Product
{
 price
 ave_user_rating
 num_ratings
 category
 
}

User wants to see Product with with the following rules

at t=t_1 : If product.category in {A,B}.

at t=t_2 : If product.category in {A,B} AND price < 100

at t=t_3 :  If product.category in {A,B}  AND price < 100 AND num_ratings >
100

You can imagine the user changing these rules in a span of less than a
minute.

I understand that Drools is designed for cases when rules changes often. But
can it support something like the one I described above where rules are
changing at a much faster rate?


Thanks.






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