[rules-users] Rules with from always loops (Drools 4.0.7)

[Edson Tirelli]

    Michal is correct. Every time a "from" expression is executed, Drools
does not know if a result for the expression is new or not and it creates a
new fact handle, bypassing the no-loop.

    []s
    Edson

2009/2/13 Michal Bali <michalbali at gmail.com>

> This is what I think is going on:when you call update($fact1) it will
> first retract $fact1 which in turn retracts $fact2, the $fact1 is then
> inserted again which cause another 'from' evaluation and a NEW $fact2 is
> pulled -> no-loop doesn't work because Drools sees it as different data
> I am just guessing here ...
>
>
> On Fri, Feb 13, 2009 at 9:12 AM, Przemysław Różycki <P.Rozycki at amg.net.pl>wrote:
>
>> Hello,
>>
>> Doesn't really anyone have any logical explanation of why such a rule
>> loops?
>>
>> To remind the rule:
>>
>> rule "Hello World"
>>        no-loop
>>        when
>>                $fact1 : MyFactBean1(  )
>>                $fact2 : MyFactBean2(  ) from $fact1
>>        then
>>                System.out.println("Fired!!!");
>>                update($fact1);
>> end
>>
>> If I don't use 'from' everything is fine.
>> I really didn't find in a documentation, that 'from' causes any special
>> behaviour of the rule looping.
>>
>> Best regards,
>> --
>> Przemysław Różycki
>> AMG.net, A Bull Group Company
>> ul. Łąkowa 29
>> 90-554 Łódź
>> www.amg.net.pl
>>
>>
>>
>> Przemysław Różycki pisze:
>>
>>  Thanks for answer, Vikrant, but I don't think so. I have always used
>>> no-loop without any additions and it worked (when I didn't use from). BTW,
>>> if you comment a condition with from, then the rule does not loop. I also
>>> checked with "no-loop true" and result is the same.
>>>
>>> Best regards,
>>> Przemek
>>>
>>> Vikrant Yagnick pisze:
>>>
>>>> I have to quickly recheck the documentation by I think you have to write
>>>> "no-loop true". Just writing no-loop defaults to false I guess.
>>>>
>>>> -----Original Message-----
>>>> From: rules-users-bounces at lists.jboss.org [mailto:
>>>> rules-users-bounces at lists.jboss.org] On Behalf Of Przemyslaw Rózycki
>>>> Sent: Tuesday, February 10, 2009 3:24 PM
>>>> To: Rules Users List
>>>> Subject: [rules-users] Rules with from always loops (Drools 4.0.7)
>>>>
>>>> Hello,
>>>>
>>>> why does such a rule always loop? Even if no-loop is used?
>>>>
>>>> rule "Hello World"
>>>>        no-loop
>>>>        when
>>>>                $fact1 : MyFactBean1(  )
>>>>                $fact2 : MyFactBean2(  ) from $fact1
>>>>        then
>>>>                System.out.println("Fired!!!");
>>>>                update($fact1);
>>>> end
>>>>
>>>> The full code of my test application and drl is attached.
>>>>
>>>> Best regards,
>>>> --
>>>> Przemysław Różycki
>>>> AMG.net, A Bull Group Company
>>>> ul. Łąkowa 29
>>>> 90-554 Łódź
>>>> www.amg.net.pl
>>>>
>>>>
>>>> MASTEK LTD.
>>>> Mastek is in NASSCOM's 'India Top 20' Software Service Exporters List.
>>>> In the US, we're called MAJESCOMASTEK
>>>>
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-- 
 Edson Tirelli
 JBoss Drools Core Development
 JBoss, a division of Red Hat @ www.jboss.com
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