Hello:
While testing my application, which uses Derby in memory-only mode, I get NPE
inside Derby under "mysterious" circumstances.
At this point, I can't even figure out what's triggering it and where this
could happen, but let me preempt my troubleshooting with some stack traces.
Perhaps someone, with good knowledge of Derby's code, may offer some
explanation. Here are some stack traces:
Mon Dec 10 12:12:36 EST 2012 Thread[DatabasePublisher[WRITER],5,main] (XID =
235), (SESSIONID = 5), (DATABASE = memory:test), (DRDAID = null), Failed
Statement is: select * from READER
java.lang.NullPointerException
at
org.apache.derby.impl.store.access.conglomerate.GenericScanController.reopenAfterEndTransaction(Unknown
Source)
at
org.apache.derby.impl.store.access.conglomerate.GenericScanController.fetchRows(Unknown
Source)
at
org.apache.derby.impl.store.access.heap.HeapScan.fetchNextGroup(Unknown Source)
at
org.apache.derby.impl.sql.execute.BulkTableScanResultSet.reloadArray(Unknown
Source)
at
org.apache.derby.impl.sql.execute.BulkTableScanResultSet.getNextRowCore(Unknown
Source)
at
org.apache.derby.impl.sql.execute.ProjectRestrictResultSet.getNextRowCore(Unknown
Source)
at
org.apache.derby.impl.sql.execute.ScrollInsensitiveResultSet.getNextRowFromSource(Unknown
Source)
at
org.apache.derby.impl.sql.execute.ScrollInsensitiveResultSet.getNextRowCore(Unknown
Source)
at
org.apache.derby.impl.sql.execute.BasicNoPutResultSetImpl.getNextRow(Unknown
Source)
at org.apache.derby.impl.jdbc.EmbedResultSet.movePosition(Unknown Source)
at org.apache.derby.impl.jdbc.EmbedResultSet.next(Unknown Source)
at QueryResults$1.hasNext(QueryResults.java:268)
at DatabasePublisher.process(DatabasePublisher.java:318)
at java.lang.Thread.run(Thread.java:662)
or
2012-12-10 12:12:36,537 [DatabasePublisher[WRITER]] ERROR QueryResults -
Unable to execute ResultSet.next() for Statement ""select * from READER"
[DERBY]"
java.sql.SQLException: Java exception: ': java.lang.NullPointerException'.
at
org.apache.derby.impl.jdbc.SQLExceptionFactory40.getSQLException(Unknown Source)
at org.apache.derby.impl.jdbc.Util.newEmbedSQLException(Unknown Source)
at org.apache.derby.impl.jdbc.Util.javaException(Unknown Source)
at
org.apache.derby.impl.jdbc.TransactionResourceImpl.wrapInSQLException(Unknown
Source)
at
org.apache.derby.impl.jdbc.TransactionResourceImpl.handleException(Unknown
Source)
at org.apache.derby.impl.jdbc.EmbedConnection.handleException(Unknown
Source)
at org.apache.derby.impl.jdbc.ConnectionChild.handleException(Unknown
Source)
at
org.apache.derby.impl.jdbc.EmbedResultSet.closeOnTransactionError(Unknown
Source)
at org.apache.derby.impl.jdbc.EmbedResultSet.movePosition(Unknown Source)
at org.apache.derby.impl.jdbc.EmbedResultSet.next(Unknown Source)
at QueryResults$1.hasNext(QueryResults.java:268)
at DatabasePublisher.process(DatabasePublisher.java:318)
at java.lang.Thread.run(Thread.java:662)
Caused by: java.sql.SQLException: Java exception: ':
java.lang.NullPointerException'.
at
org.apache.derby.impl.jdbc.SQLExceptionFactory.getSQLException(Unknown Source)
at
org.apache.derby.impl.jdbc.SQLExceptionFactory40.wrapArgsForTransportAcrossDRDA(Unknown
Source)
... 14 more
Caused by: java.lang.NullPointerException
at
org.apache.derby.impl.store.access.conglomerate.GenericScanController.reopenAfterEndTransaction(Unknown
Source)
at
org.apache.derby.impl.store.access.conglomerate.GenericScanController.fetchRows(Unknown
Source)
at
org.apache.derby.impl.store.access.heap.HeapScan.fetchNextGroup(Unknown Source)
at
org.apache.derby.impl.sql.execute.BulkTableScanResultSet.reloadArray(Unknown
Source)
at
org.apache.derby.impl.sql.execute.BulkTableScanResultSet.getNextRowCore(Unknown
Source)
at
org.apache.derby.impl.sql.execute.ProjectRestrictResultSet.getNextRowCore(Unknown
Source)
at
org.apache.derby.impl.sql.execute.ScrollInsensitiveResultSet.getNextRowFromSource(Unknown
Source)
at
org.apache.derby.impl.sql.execute.ScrollInsensitiveResultSet.getNextRowCore(Unknown
Source)
at
org.apache.derby.impl.sql.execute.BasicNoPutResultSetImpl.getNextRow(Unknown
Source)
... 6 more
One more thing I can share is that this seems to also be a timing problem - if
the code is executed slowly, line-by-line in the debugger, then this problem
doesn't occur. But if run at full speed, then these exceptions are thrown. The
problem is not intermittent and easily reproduced 100% of the time on my end.
Any thoughts would be greatly appreciated.
Pavel.
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