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From Pavel Bortnovskiy <pbortnovs...@jefferies.com>
Subject RE: NPE
Date Mon, 10 Dec 2012 20:54:47 GMT
Thanks, Dag. Yeah, I wish I could figure out how to make a self-contained test prog which can
reproduce it. I will try.
Although I do agree with you that it looks like a race condition, I can reproduce it (within
my program)
with 100% certainty - every time. However, it might be worth stating the following:
my program is written as plug-n-play modules. When I plug in any other module, the error never
occurs (or is well-masked).
It's only with this newly written module, that it started to fail.

In the meantime, what might be causing the container to be NULL?
Is it possible that there is a bug in my program which sets it to NULL (or does not assign
it) in such a way that other parts of Derby do not fail nor notice that it is NULL?

-----Original Message-----
From: Dag Wanvik [mailto:dag.wanvik@oracle.com]
Sent: Monday, December 10, 2012 3:15 PM
To: derby-user@db.apache.org
Subject: Re: NPE


On 10.12.2012 19:21, Pavel Bortnovskiy wrote:
> I upgraded to 10.9.1.0 and rerun with debug libraries (please disregard my previous message).
>
> Mon Dec 10 13:19:44 EST 2012
> Thread[DatabasePublisher[BOND_WRITER],5,main] (XID = 289), (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(GenericScanController.java:1048)
>         at

It looks like "container" is null, cf. the line 1048:

        case SCAN_HOLD_INIT:
***>         reusableRecordIdSequenceNumber =
                container.getReusableRecordIdSequenceNumber();

i.e. has been closed, cf the assignment just above:

        ContainerHandle container = open_conglom.reopen();

The call to reopen just returns null if OpenConglomerate has been closed somehow.

Smells like a race condition of sorts, maybe some missing synchronization in the Derby code.
If you are able to post a self contained repro program, although this might be tricky if this
is indeed a race, this would increase your chances of having this fixed soon..

Thanks,
Dag


 In any case the NullPointerException shoudln't be seen by the application code, so this is
a bug.


> org.apache.derby.impl.store.access.conglomerate.GenericScanController.fetchRows(GenericScanController.java:622)
>         at org.apache.derby.impl.store.access.heap.HeapScan.fetchNextGroup(HeapScan.java:322)
>         at org.apache.derby.impl.sql.execute.BulkTableScanResultSet.reloadArray(BulkTableScanResultSet.java:353)
>         at org.apache.derby.impl.sql.execute.BulkTableScanResultSet.getNextRowCore(BulkTableScanResultSet.java:308)
>         at org.apache.derby.impl.sql.execute.ProjectRestrictResultSet.getNextRowCore(ProjectRestrictResultSet.java:261)
>         at org.apache.derby.impl.sql.execute.ScrollInsensitiveResultSet.getNextRowFromSource(ScrollInsensitiveResultSet.java:801)
>         at org.apache.derby.impl.sql.execute.ScrollInsensitiveResultSet.getNextRowCore(ScrollInsensitiveResultSet.java:518)
>         at org.apache.derby.impl.sql.execute.BasicNoPutResultSetImpl.getNextRow(BasicNoPutResultSetImpl.java:478)
>         at org.apache.derby.impl.jdbc.EmbedResultSet.movePosition(EmbedResultSet.java:432)
>         at org.apache.derby.impl.jdbc.EmbedResultSet.next(EmbedResultSet.java:376)
>         at QueryResults$1.hasNext(QueryResults.java:268)
>         at DatabasePublisher.process(DatabasePublisher.java:318)
>         at java.lang.Thread.run(Thread.java:662)
>
> -----Original Message-----
> From: Rick Hillegas [mailto:rick.hillegas@oracle.com]
> Sent: Monday, December 10, 2012 1:05 PM
> To: derby-user@db.apache.org
> Subject: Re: NPE
>
> Hi Pavel,
>
> Can you reproduce this problem with the debug version of Derby? That would give us line
numbers in the stack trace.
>
> Thanks,
> -Rick
>
> On 12/10/12 9:23 AM, Pavel Bortnovskiy wrote:
>> 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(Unkno
>> w
>> n Source)
>>
>> at
>> org.apache.derby.impl.sql.execute.BulkTableScanResultSet.reloadArray(
>> U
>> nknown
>> Source)
>>
>> at
>> org.apache.derby.impl.sql.execute.BulkTableScanResultSet.getNextRowCo
>> r
>> e(Unknown
>> Source)
>>
>> at
>> org.apache.derby.impl.sql.execute.ProjectRestrictResultSet.getNextRow
>> C
>> ore(Unknown
>> Source)
>>
>> at
>> org.apache.derby.impl.sql.execute.ScrollInsensitiveResultSet.getNextR
>> o
>> wFromSource(Unknown
>> Source)
>>
>> at
>> org.apache.derby.impl.sql.execute.ScrollInsensitiveResultSet.getNextR
>> o
>> wCore(Unknown
>> Source)
>>
>> at
>> org.apache.derby.impl.sql.execute.BasicNoPutResultSetImpl.getNextRow(
>> U
>> nknown
>> 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(Unkn
>> o
>> wn
>> 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(Un
>> k
>> nown
>> 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(Unk
>> n
>> own
>> 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(Unknow
>> n
>> Source)
>>
>> at
>> org.apache.derby.impl.jdbc.SQLExceptionFactory40.wrapArgsForTransport
>> A
>> crossDRDA(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(Unkno
>> w
>> n Source)
>>
>> at
>> org.apache.derby.impl.sql.execute.BulkTableScanResultSet.reloadArray(
>> U
>> nknown
>> Source)
>>
>> at
>> org.apache.derby.impl.sql.execute.BulkTableScanResultSet.getNextRowCo
>> r
>> e(Unknown
>> Source)
>>
>> at
>> org.apache.derby.impl.sql.execute.ProjectRestrictResultSet.getNextRow
>> C
>> ore(Unknown
>> Source)
>>
>> at
>> org.apache.derby.impl.sql.execute.ScrollInsensitiveResultSet.getNextR
>> o
>> wFromSource(Unknown
>> Source)
>>
>> at
>> org.apache.derby.impl.sql.execute.ScrollInsensitiveResultSet.getNextR
>> o
>> wCore(Unknown
>> Source)
>>
>> at
>> org.apache.derby.impl.sql.execute.BasicNoPutResultSetImpl.getNextRow(
>> U
>> nknown
>> 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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>
> 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.


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.

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