In my use case, I have ~ 200,000 rows in a table that I need lookup in order to price an item. Rather than load the entire table into working memory,I'm trying load the relevant rows (based on a matching criteria) and load those as facts and then have my rules evaluate the loaded facts. Based on that I've got the following rule : rule "Load pricelist" salience 10000 when $priceUnit : PriceUnit() not ( exists Pricelist( id.prodid == $priceUnit.prodid ) ) $unitPrices : ArrayList() from collect ( Pricelist() from PricelistUtilities.getPriceLists($priceUnit.prodid) ) then for( Pricelist priceList : (List<Pricelist>) $unitPrices ) { insert (priceList); } end In the rule above - 'PriceUnit' is the unit that I'm trying to price. And 'Pricelist' is the facts that I'm trying to fetch from a table based on the prodid matching and inserting those into WM. The PricelistUtilities.getPriceList returns a list of price list items that match the 'Product id' (prodid). In the RHS, all I'm trying to iterate over the list of pricelists and then insert those into WM. When I execute the rule above, I can see that the rule is executing the 'select' to load pricelists : Hibernate: /* from PriceList where status = 'A' and end_date >= current_date and prodid = '010366' and cover_grade = 'LF' */ select pricelist0_.prodid as prodid1_, pricelist0_.cover_grade as cover2_1_, pricelist0_.cover_series as cover3_1_, pricelist0_.cover_color as cover4_1_, pricelist0_.division as division1_, pricelist0_.location as location1_, pricelist0_.list as list1_, pricelist0_.start_date as start8_1_, pricelist0_.end_date as end9_1_, pricelist0_.timestamp as timestamp1_, pricelist0_.status as status1_, pricelist0_.sold_flag as sold12_1_, pricelist0_.base_price as base13_1_, pricelist0_.list_price as list14_1_, pricelist0_.add_on as add15_1_, pricelist0_.landed_frt as landed16_1_ from catalog.pricelist pricelist0_ where pricelist0_.status='A' and end_date>=current_date and prodid='123456' However, I get an java.util.ConcurrentModificationException when the rule fires : org.drools.runtime.rule.ConsequenceException: rule: Load pricelist at org.drools.runtime.rule.impl.DefaultConsequenceExceptionHandler.handleException(DefaultConsequenceExceptionHandler.java:39) at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1101) at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:1029) at org.drools.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1251) at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:737) at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:701) at org.drools.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:218) at com.generic.rules.utils.DroolsTest.main(DroolsTest.java:46) Caused by: java.util.ConcurrentModificationException at java.util.AbstractList$Itr.checkForComodification(AbstractList.java:372) at java.util.AbstractList$Itr.next(AbstractList.java:343) at com.sample.Rule_Load_pricelist_0.defaultConsequence(Rule_Load_pricelist_0.java:7) at com.sample.Rule_Load_pricelist_0DefaultConsequenceInvoker.evaluate(Rule_Load_pricelist_0DefaultConsequenceInvoker.java:27) at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1091) ... 6 more If I comment the check for existing PriceList Items 'not ( exists Pricelist( id.prodid == $priceUnit.prodid ) )', then it works fine. But as soon as I add the check back, it breaks. Is this a bug or am I doing something wrong ? Any help / insight will be appreciated. Thanks in advance. -- View this message in context: http://drools.46999.n3.nabble.com/ConcurrentModificationException-loading... 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