NPE or assert failure printed when dropping table while statistics are written
out
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Key: DERBY-5124
URL: https://issues.apache.org/jira/browse/DERBY-5124
Project: Derby
Issue Type: Bug
Components: Services
Affects Versions: 10.8.0.0
Reporter: Knut Anders Hatlen
To find out what would happen if a table was dropped while its statistics were
being written to disk, I put a breakpoint in
IndexStatisticsImpl.writeUpdatedStats() right after the call to
dropStatisticsDescriptors(), started an ij session in the debugger and executed
some statements to make the istat code kick in. When the breakpoint was hit, I
dropped the table being updated in ij, before letting the istat thread continue.
With insane jars, the following NPE was printed on the ij console:
Exception in thread "index-stat-thread" java.lang.NullPointerException
at
org.apache.derby.impl.services.daemon.IndexStatisticsDaemonImpl.writeUpdatedStats(IndexStatisticsDaemonImpl.java:556)
at
org.apache.derby.impl.services.daemon.IndexStatisticsDaemonImpl.updateIndexStatsMinion(IndexStatisticsDaemonImpl.java:486)
at
org.apache.derby.impl.services.daemon.IndexStatisticsDaemonImpl.generateStatistics(IndexStatisticsDaemonImpl.java:323)
at
org.apache.derby.impl.services.daemon.IndexStatisticsDaemonImpl.processingLoop(IndexStatisticsDaemonImpl.java:759)
at
org.apache.derby.impl.services.daemon.IndexStatisticsDaemonImpl.run(IndexStatisticsDaemonImpl.java:675)
at java.lang.Thread.run(Thread.java:662)
Apart from the stack trace being printed, nothing bad happened. The istat
thread was able to recover, and the ij session was unaffected too.
Using a debug build, I got an assert failure instead:
Exception in thread "index-stat-thread"
org.apache.derby.shared.common.sanity.AssertFailure: ASSERT FAILED transaction
not pristine
at
org.apache.derby.shared.common.sanity.SanityManager.THROWASSERT(SanityManager.java:162)
at
org.apache.derby.shared.common.sanity.SanityManager.THROWASSERT(SanityManager.java:147)
at
org.apache.derby.impl.services.daemon.IndexStatisticsDaemonImpl.processingLoop(IndexStatisticsDaemonImpl.java:810)
at
org.apache.derby.impl.services.daemon.IndexStatisticsDaemonImpl.run(IndexStatisticsDaemonImpl.java:675)
at java.lang.Thread.run(Thread.java:662)
The assert failure prevented some cleanup from happening, so the istat thread
seemed to hold on to a lock on SYSSTATISTICS, so the following statement would
keep failing in ij after on:
ij> select * from sys.sysstatistics;
STATID |REFERENCEID
|TABLEID |CREATIONTIMESTAMP
|&|VALID|COLCOUNT |STATISTICS
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
ERROR 40XL1: A lock could not be obtained within the time requested
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