HashJoinStrategy leads to java.lang.OutOfMemoryError
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Key: DERBY-106
URL: http://nagoya.apache.org/jira/browse/DERBY-106
Project: Derby
Type: Bug
Reporter: Gerald Khin
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!
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