May be I have not put the question right. We have a drool rule that is running
extremely slow for large sets of data. The rule is something like:
For every object A, perform action if there does not exist an object B such
that A.id = B.id.
And the corresponding drool rule is as follows:
when
A()
not(exists B(A.id = id))
then
action......
The performance is bad because of not exists clause here. We have got OOM
exceptions with relatively large amounts of data for this rule. To improve
performance, we basically hacked the rule/code into something like this:
Create a global variable x that is a HashSet of all ids of object A, and the
drool rule now is:
global java.util.HashSet x;
when
B()
eval
(
! (x.contains(b.id) )
)
then
action.....
This obviously is performing much better with hashes involved. But, I don't
like the fact that we have to write the logic of this rule at two places. I
would rather create this variable x (don't care whether it is global or
temporarily bound) in the rule itself and use it in the condition to help
performance and have all logic for the rule at one place.
Is there a way to generate this hashset x in the condition part of the rule
itself? Yes, I understand that I am trying to mix up the procedural part of
code with drool code. But, I was just wondering if this is possible to keep the
java code clean and have the intelligence of information that the rule needs to
be evaluated in the rule itself.
Hope this clears some doubts.
Thanks
Malay Shah
-----Original Message-----
From: rules-users-boun...@lists.jboss.org
[mailto:rules-users-boun...@lists.jboss.org] On Behalf Of Greg Barton
Sent: Friday, August 21, 2009 4:44 PM
To: Rules Users List
Subject: Re: [rules-users] populating global variable in Condition Section?
This is a galactically bad idea. Using a global in this way is inherently
unsafe as there's no guarantee that ebtween the time you set the var and when
it's used later in the condition that the value is the same. What is your
reason for wanting to use a global in this way? You should use a temporary
bound variable instead.
--- On Fri, 8/21/09, Shah, Malay <malay.s...@morganstanley.com> wrote:
> From: Shah, Malay <malay.s...@morganstanley.com>
> Subject: [rules-users] populating global variable in Condition Section?
> To: rules-users@lists.jboss.org
> Date: Friday, August 21, 2009, 3:19 PM
>
>
>
>
>
>
> Hi,
>
> Is it possible
> to populate a global variable in
> the condition section of the
> drool rule, and use it later in the condition itself?
> I currently have a
> global HashSet variable that I construct before firing the rule, but I
> would like this code of constructing this global variable to be with
> the drool rule itself. Any help on this would be much appreciated.
>
> Thanks
>
> Malay
>
>
>
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