[rules-users] Using collect to group by

[Heyns, Juan]

Hello,



I am trying to achieve something like a SQL statement equivalent of:



SELECT    r.property1 AS p1, r.property2 AS p2,
SOME_CALCULATION(r.property3) AS p3

FROM      right AS r

GROUP BY  p2, p3



I am not sure if this is valid SQL since I am grouping by a calculated
value, but that aside.



I am asserting the Rights objects into the working memory and then would
like to execute a rule on the objects based

on a grouping of objects. The first property is directly accessible from
the object right.getProperty2() but the

second property is only accessible through a lookup
MyClass.staticMethod(right.getProperty3()).



As far as I have it the rule should make use of something like collect
or accumulate but I do not know how to

achieve this without also asserting the properties objects into the
memory as well. And even if I assert the properties

objects into the working memory I do not know how to group by the second
property.



rule "Calculate something"

     no-loop

     when

           $rights: ArrayList( )

                   from collect( Right( ) );



     then

           // execute rule

end



Could you please give me some assistance?



Regards

Juan



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