[rules-users] How to design a rule using collect for filtering? Thanks.

[Edson Tirelli]

   No single simple answer here. You need to check what would better fit
your use case.
   The thing is: it is not possible to limit the number of matches to a
collect statement... all matching instances WILL match it and be collected.

   No really "clean" way I can think about, but a few possible options
(haven't executed them, but shall work):

1. Simply execute the actions multiple times in the consequence:

when
   eventList : LinkedList( $size : size >= 5 ) from collect( Event(text
matches ".*rule5.*" ))
*then
   for( int i = 0; i < $size/5; i++ )
*
       System.out.println("rule5 is fired " + eventList.size());
end

2. Flag used facts:

when
    eventList : LinkedList( size >= 5 ) from collect( Event(text matches
".*rule5.*", processed == false ))
*then
*   System.out.println("rule5 is fired " + eventList.size());
*    for( int i = 0; i < 5; i++ ) {
       Event e = **(Event) eventList.get( i );**
       e.setProcessed( true );
       update( e );
*
   }
end

2. Retract used facts:

when
    eventList : LinkedList( size >= 5 ) from collect( Event(text matches
".*rule5.*" ))
*then
*   System.out.println("rule5 is fired " + eventList.size());
*    for( int i = 0; i < 5; i++ ) {
       Event e = **(Event) eventList.get( i );**
       retract( e );
 *
   }
end

    Hope it helps.

    Edson

2007/8/10, Anh Vuong <anhtvuong at yahoo.com>:
>
> Hi,
> I'd like to use keyword collect to do my filtering but its behaviour
> confused me, please advise. I greatly appreciate your help.
>
> Problem 1:
>
> when
> eventList : LinkedList(size == 5)
> from collect( Event(text matches
> ".*rule5.*" ))
> *then* System.out.println(
> "rule5 is fired " + eventList.size());
> I still do not see any log msg after adding 5+ events. Is something wrong
> with my rule?
>
> Problem 2:
>
> when
> event: Event(text matches ".*rule5.*" ))
> eventList : LinkedList(size == 5)
> from collect( Event(text == event.text)
>  *then* System.out.println(
> "rule5 is fired " + eventList.size());
> After adding 5 events, I see 5 log msg instead of one as I'd expect.
> If I add more events, I will see more log. How do I tell LHS  to reset the
> count from 0.
> Basically, I want to take 1 event out of 5 similar events (suppressing
> filtering). So if there are 10 similar events, my RHS should activate 2
> times, not 10 times.
>
> Thanks,
> -av
>
>
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-- 
  Edson Tirelli
  Software Engineer - JBoss Rules Core Developer
  Office: +55 11 3529-6000
  Mobile: +55 11 9287-5646
  JBoss, a division of Red Hat @ www.jboss.com
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