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.


Jefferies archives and monitors outgoing and incoming e-mail. The contents of this email, including any attachments, are confidential to the ordinary user of the email address to which it was addressed. If you are not the addressee of this email you may not copy, forward, disclose or otherwise use it or any part of it in any form whatsoever. This email may be produced at the request of regulators or in connection with civil litigation. Jefferies accepts no liability for any errors or omissions arising as a result of transmission. Use by other than intended recipients is prohibited. In the United Kingdom, Jefferies operates as Jefferies International Limited; registered in England: no. 1978621; registered office: Vintners Place, 68 Upper Thames Street, London EC4V 3BJ. Jefferies International Limited is authorised and regulated by the Financial Services Authority.