Hi, I am facing an issue with Drools Query. Our application serializes working memory after its each execution, to save the rule engine state. Our rule base contains a Query along with other rules: query "GetFactsByValue" ( String $value ) Facts : DataObject( stringValue == $value ) end With this query present in Rule Base, if I insert more then 900 instances of DataObject & then try to serialize the working memory... serialization fails with bellow error: java.lang.StackOverflowError at java.io.ObjectStreamClass.processQueue(Unknown Source) at java.io.ObjectStreamClass.lookup(Unknown Source) at java.io.ObjectOutputStream.writeObject0(Unknown Source) at java.io.ObjectOutputStream.defaultWriteFields(Unknown Source) at java.io.ObjectOutputStream.writeSerialData(Unknown Source) at java.io.ObjectOutputStream.writeOrdinaryObject(Unknown Source) at java.io.ObjectOutputStream.writeObject0(Unknown Source) at java.io.ObjectOutputStream.defaultWriteFields(Unknown Source) at java.io.ObjectOutputStream.writeSerialData(Unknown Source) at java.io.ObjectOutputStream.writeOrdinaryObject(Unknown Source) But if I remove the query from rule base, I can insert more then 60,000 objects & then serialize WM without any problem. Not sure if this is a bug in Query feature or problem in the way I have written the Query. I have attached test files. We are using few more queries in our RuleBase like: query "GetAllFacts" ( ) Fact : DataObject( ) end query "GetFactsByDate" ( Calendar $startDate, Calendar $endDate ) Fact : DataObject( startDate >= $startDate, endDate <= $endDate ) end query "GetFactsByParamIdTimeRange" ( ArrayList $paramIDs, Calendar $startDate, Calendar $endDate ) Facts : DataObject( paramID memberOf $paramIDs, startDate >= $startDate, endDate <= $endDate ) end Not sure if they also may fail in some special scenarios. Atleast last 3 Queries we are planning to use in our production. Is it ok to use those? Execution Environment: OS: Windows/ Solaris Drools 4.0.7 jre1.5.0_09 Thanks Siddhartha