Major Description
My application is running out of memory: I encounterd a java.lang.OutOfMemoryError. I used -Xmx256M. Unfortunatley, I cannot spend an arbitrary amount of JVM memory.
Then, I commented out the line in class OptimizerFactoryImpl which was adding the HashJoinStrategy to the set of Join strategies:
if (joinStrategySet == null)
{ // JoinStrategy[] jss = new JoinStrategy[2]; JoinStrategy[] jss = new JoinStrategy[1]; jss[0] = new NestedLoopJoinStrategy(); // jss[1] = new HashJoinStrategy(); joinStrategySet = jss; }And with these changes the OutOfMemoryError has gone away! And it works even with -Xmx128M!!!
So I guess that there is a major memory issue with this HashJoin strategy implementation.
If it turns out to be too complicated to make the memory consumption more predicatble or even bounded to some configurable limit, then I need at least as a workaround a way to turn off the HashJoin strategy completely: I did it by patching and building my own derby.jar, but if there would be an official solution with some kind of switch like a system property, it would be great!