The alternative you're attempting using "from" is potentially less efficient than the first one you tried. :) Can you alter the CurrentFact objects to hold current and previous state?  That way you avoid the matching step altogether. rule "Interesting Event" when $currentFact: CurrentFact(state=="somethingNew", previousState=="somethingOld") then //do something //update currentFact.previousState to reflect the state of the newFact end ----- Original Message ----- From: rogelio_sevilla1 <rogelio.sevilla1(a)gmail.com&gt; To: rules-users(a)lists.jboss.org Cc: Sent: Thursday, August 2, 2012 7:19 PM Subject: [rules-users] Avoid caching method results within non fact objects Good day everyone, I'm having a problem here and I'm not sure if I'm using the right approach. Currently I have a couple of rules where I inject A LOT of objects as facts. These objects change their states quite commonly and I have to make decisions when the previous state has a particular value comparing it to the current state.  Something like this (just an example, sorry if there are typos) rule "Interesting Event" when $currentFact: CurrentFact(state=="somethingNew") $previousFact: PreviousFact($currentFact.id == id && state=="somethingOld") then //do something //update previousFact to reflect the state of the newFact end The problem that I had with this is that I had SOOO much facts within the rules session (thousands of objects with a lot of data that I need within the session too) that the fireAllRules method started to take too much time to complete. So, what I did is to store the previous facts of the objects within a Wrapper class that contains a hashmap with all of these states. Something like: PreviousStateHolder{ private static HashMap<String,PreviousFact> previousFacts; public void insertPreviousState(){ ... } public boolean containsPreviousState(CurrentState currentState){ ... } public boolean deletePreviousState(){ ... } .. other management methods } And my new rules look like rule "Interesting Event" when $currentFact: CurrentFact(state=="somethingNew") $previousFact: PreviousFact(state=="somethingOld")                     from PreviousStateHolder.retrievePreviousState($currentFact) then //do something //update previousFact to reflect the state of the newFact end The problem is that drools caches the result returned by the retrievePreviousState()  method, so, it does not matter if the PreviousStateHolder member changes; drools always caches the result. I have tried to put my invocations within eval() but I still get the same problem (cached results). I know they are being cached because I put a breakpoint within the methods, and the first time the fireAllRules gets executed, they get hit. But then, the consequence of these rules keep getting executed even if the retrievePreviousState() does not reflect the value needed to do so. Am I doing something wrong?? Is there another approach that does not involve inserting all of these states as facts within my session?? Thanks a lot in advance -- View this message in context: http://drools.46999.n3.nabble.com/Avoid-caching-method-results-within-non... Sent from the Drools: User forum mailing list archive at Nabble.com. _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users

Thanks Laune and Greg, Yes, I'm pretty positive that the amount of facts are the real problem in my situation. Currently I have only 3 rules, and the first one is in charge of creating the previous state from a current fact in case it has not been created. If the session receives a current fact for the first time, this rule creates the previous state object so it can be updated within other rules. I have something like this (just a example, sorry for typos): rule "State Generator" when $currentFact : CurrentFact() not PreviousFact(id == $currentFact.id) then PreviousFact previousFact = new PreviousFact(); previousFact.cloneThis($currentFact) insert(previousFact) <-- this takes a lot of time end That's why I would really like to avoid inserting these states within the working memory. When I started storing them in the Wrapper Hash, the fireAllRules went from 80 seconds of execution to 7 seconds. Thanks a lot in advance for your advice. -- View this message in context: http://drools.46999.n3.nabble.com/Avoid-caching-method-results-within-non... Sent from the Drools: User forum mailing list archive at Nabble.com.