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From Mike Matrigali <mikem_...@sbcglobal.net>
Subject Re: [jira] Created: (DERBY-106) HashJoinStrategy leads to java.lang.OutOfMemoryError
Date Fri, 17 Dec 2004 16:34:23 GMT
Hash: SHA1

could you post the query and the associated base table and index ddl
which caused this.  The
optimizer tries to only pick hash join when it thinks the memory needed
will be small, so you may have found an optimizer bug - or maybe you
need an index somewhere?

Gerald Khin (JIRA) wrote:
| HashJoinStrategy leads to java.lang.OutOfMemoryError
| ----------------------------------------------------
|          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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