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Posted to dev@jena.apache.org by "Simon Helsen (Commented) (JIRA)" <ji...@apache.org> on 2011/11/03 20:53:32 UTC
[jira] [Commented] (JENA-131) TxTDB problem during concurrent
execution
[ https://issues.apache.org/jira/browse/JENA-131?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13143485#comment-13143485 ]
Simon Helsen commented on JENA-131:
-----------------------------------
I finally found some time to investigate this further. This is quite tricky for me since I don't know much of the transaction code, but I can try to gather evidence which may show the problematic path. First, in order to find out what the path is of the concurrent threads trying to remove the iterator, I had to instrument the Transaction code. I replaced the one-liner :
public void removeIterator(Iterator<?> iter) { iterators.remove(iter) ; }
with the following:
private StackTraceElement[] enteredThread = null;
private String previousThreadName = null;
public void removeIterator(Iterator<?> iter) {
StackTraceElement[] previousThread = enteredThread;
if (previousThread != null) {
System.out.println("2 threads accessing removeIterator at the same time in transaction " + this.toString());
System.out.println("previous thread:" + previousThreadName);
for(int i = 0; i < previousThread.length; i++) {
System.out.println(previousThread[i].toString());
}
System.out.println("current thread:" + Thread.currentThread().getName());
StackTraceElement[] currentStackTrace = Thread.currentThread().getStackTrace();
for(int i = 0; i < currentStackTrace.length; i++) {
System.out.println(currentStackTrace[i].toString());
}
}
enteredThread = Thread.currentThread().getStackTrace();
previousThreadName = Thread.currentThread().getName();
iterators.remove(iter) ;
enteredThread = null;}
Now, in order to show that the threads which concurrently try to remove the iterator are actually being started in separated transactions (different ones it turns out - see below), I also instrumented my own invocation in the respective JenaTdbTxProvider.storeOperation methods (as you will see from the traces below). I got some curious results:
starting Transaction: 102 : Mode=READ : State=ACTIVE : D:\jfsDev\working_dir\indices\0ed6df84396e4d16801f7daf97c16ecb\jfs-rdfindex\ in thread 300814830@qtp-48235232-6
starting Transaction: 117 : Mode=READ : State=ACTIVE : D:\jfsDev\working_dir\indices\0ed6df84396e4d16801f7daf97c16ecb\jfs-rdfindex\ in thread 81462491@qtp-48235232-5
2 threads accessing removeIterator at the same time in transaction Transaction: 94 : Mode=WRITE : State=CLOSED : D:\jfsDev\working_dir\indices\0ed6df84396e4d16801f7daf97c16ecb\jfs-rdfindex\
previous thread:300814830@qtp-48235232-6
java.lang.Thread.getStackTraceImpl(Native Method)
java.lang.Thread.getStackTrace(Thread.java:1042)
com.hp.hpl.jena.tdb.transaction.Transaction.removeIterator(Transaction.java:207)
com.hp.hpl.jena.tdb.transaction.BlockMgrJournal.endIterator(BlockMgrJournal.java:312)
com.hp.hpl.jena.tdb.base.block.BlockMgrWrapper.endIterator(BlockMgrWrapper.java:134)
com.hp.hpl.jena.tdb.base.recordbuffer.RecordRangeIterator.close(RecordRangeIterator.java:155)
com.hp.hpl.jena.tdb.base.recordbuffer.RecordRangeIterator.hasNext(RecordRangeIterator.java:112)
org.openjena.atlas.iterator.Iter$4.hasNext(Iter.java:287)
com.hp.hpl.jena.tdb.sys.DatasetControlMRSW$IteratorCheckNotConcurrent.hasNext(DatasetControlMRSW.java:119)
org.openjena.atlas.iterator.Iter$3.hasNext(Iter.java:173)
org.openjena.atlas.iterator.Iter$4.hasNext(Iter.java:287)
org.openjena.atlas.iterator.Iter$3.hasNext(Iter.java:173)
org.openjena.atlas.iterator.Iter.hasNext(Iter.java:766)
org.openjena.atlas.iterator.RepeatApplyIterator.hasNext(RepeatApplyIterator.java:42)
org.openjena.atlas.iterator.Iter$4.hasNext(Iter.java:287)
com.hp.hpl.jena.sparql.engine.iterator.QueryIterPlainWrapper.hasNextBinding(QueryIterPlainWrapper.java:54)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
com.hp.hpl.jena.sparql.engine.iterator.QueryIterConcat.hasNextBinding(QueryIterConcat.java:83)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
com.hp.hpl.jena.sparql.engine.iterator.QueryIterRepeatApply.hasNextBinding(QueryIterRepeatApply.java:79)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
com.hp.hpl.jena.sparql.engine.iterator.QueryIterProcessBinding.hasNextBinding(QueryIterProcessBinding.java:60)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
com.hp.hpl.jena.sparql.engine.iterator.QueryIterPeek.hasNextBinding(QueryIterPeek.java:57)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
org.openjena.atlas.iterator.Iter$4.hasNext(Iter.java:287)
org.openjena.atlas.iterator.RepeatApplyIterator.hasNext(RepeatApplyIterator.java:46)
org.openjena.atlas.iterator.Iter$4.hasNext(Iter.java:287)
com.hp.hpl.jena.sparql.engine.iterator.QueryIterPlainWrapper.hasNextBinding(QueryIterPlainWrapper.java:54)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
com.hp.hpl.jena.sparql.engine.iterator.QueryIterConvert.hasNextBinding(QueryIterConvert.java:65)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
com.hp.hpl.jena.sparql.engine.iterator.QueryIterSlice.hasNextBinding(QueryIterSlice.java:76)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorWrapper.hasNextBinding(QueryIteratorWrapper.java:40)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorWrapper.hasNextBinding(QueryIteratorWrapper.java:40)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
com.hp.hpl.jena.sparql.engine.ResultSetStream.hasNext(ResultSetStream.java:72)
com.ibm.team.jfs.rdf.internal.jena.InternalResultSet.retrieveFirstPage(InternalResultSet.java:61)
com.ibm.team.jfs.rdf.internal.jena.tdb.JenaTdbTxProvider.renderSelect(JenaTdbTxProvider.java:1756)
com.ibm.team.jfs.rdf.internal.jena.tdb.JenaTdbTxProvider.performSelect(JenaTdbTxProvider.java:1510)
com.ibm.team.jfs.rdf.internal.jena.tdb.JenaTdbTxProvider$15.run(JenaTdbTxProvider.java:1626)
com.ibm.team.jfs.rdf.internal.jena.tdb.JenaTdbTxProvider$15.run(JenaTdbTxProvider.java:1)
com.ibm.team.jfs.rdf.internal.jena.tdb.JenaTdbTxProvider.storeOperation(JenaTdbTxProvider.java:196)
current thread:81462491@qtp-48235232-5
java.lang.Thread.getStackTraceImpl(Native Method)
java.lang.Thread.getStackTrace(Thread.java:1042)
com.hp.hpl.jena.tdb.transaction.Transaction.removeIterator(Transaction.java:202)
com.hp.hpl.jena.tdb.transaction.BlockMgrJournal.endIterator(BlockMgrJournal.java:312)
com.hp.hpl.jena.tdb.transaction.BlockMgrJournal.endIterator(BlockMgrJournal.java:313)
com.hp.hpl.jena.tdb.transaction.BlockMgrJournal.endIterator(BlockMgrJournal.java:313)
com.hp.hpl.jena.tdb.base.block.BlockMgrWrapper.endIterator(BlockMgrWrapper.java:134)
com.hp.hpl.jena.tdb.base.recordbuffer.RecordRangeIterator.close(RecordRangeIterator.java:155)
com.hp.hpl.jena.tdb.base.recordbuffer.RecordRangeIterator.hasNext(RecordRangeIterator.java:112)
org.openjena.atlas.iterator.Iter$4.hasNext(Iter.java:287)
com.hp.hpl.jena.tdb.sys.DatasetControlMRSW$IteratorCheckNotConcurrent.hasNext(DatasetControlMRSW.java:119)
org.openjena.atlas.iterator.Iter$3.hasNext(Iter.java:173)
org.openjena.atlas.iterator.Iter$4.hasNext(Iter.java:287)
org.openjena.atlas.iterator.Iter$3.hasNext(Iter.java:173)
org.openjena.atlas.iterator.Iter.hasNext(Iter.java:766)
org.openjena.atlas.iterator.RepeatApplyIterator.hasNext(RepeatApplyIterator.java:42)
org.openjena.atlas.iterator.Iter$4.hasNext(Iter.java:287)
com.hp.hpl.jena.sparql.engine.iterator.QueryIterPlainWrapper.hasNextBinding(QueryIterPlainWrapper.java:54)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
com.hp.hpl.jena.sparql.engine.iterator.QueryIterProcessBinding.hasNextBinding(QueryIterProcessBinding.java:60)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
com.hp.hpl.jena.sparql.engine.iterator.QueryIterConcat.hasNextBinding(QueryIterConcat.java:83)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
com.hp.hpl.jena.sparql.engine.iterator.QueryIterRepeatApply.hasNextBinding(QueryIterRepeatApply.java:79)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
com.hp.hpl.jena.sparql.engine.iterator.QueryIterConcat.hasNextBinding(QueryIterConcat.java:83)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
com.hp.hpl.jena.sparql.engine.iterator.QueryIterRepeatApply.hasNextBinding(QueryIterRepeatApply.java:79)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
com.hp.hpl.jena.sparql.engine.iterator.QueryIterPeek.hasNextBinding(QueryIterPeek.java:57)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
org.openjena.atlas.iterator.Iter$4.hasNext(Iter.java:287)
org.openjena.atlas.iterator.RepeatApplyIterator.hasNext(RepeatApplyIterator.java:46)
org.openjena.atlas.iterator.Iter$4.hasNext(Iter.java:287)
com.hp.hpl.jena.sparql.engine.iterator.QueryIterPlainWrapper.hasNextBinding(QueryIterPlainWrapper.java:54)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
com.hp.hpl.jena.sparql.engine.iterator.QueryIterProcessBinding.hasNextBinding(QueryIterProcessBinding.java:60)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
com.hp.hpl.jena.sparql.engine.iterator.QueryIterProcessBinding.hasNextBinding(QueryIterProcessBinding.java:60)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
com.hp.hpl.jena.sparql.engine.iterator.QueryIterConvert.hasNextBinding(QueryIterConvert.java:65)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
com.hp.hpl.jena.sparql.engine.iterator.QueryIterSlice.hasNextBinding(QueryIterSlice.java:76)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorWrapper.hasNextBinding(QueryIteratorWrapper.java:40)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorWrapper.hasNextBinding(QueryIteratorWrapper.java:40)
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
com.hp.hpl.jena.sparql.engine.ResultSetStream.hasNext(ResultSetStream.java:72)
com.ibm.team.jfs.rdf.internal.jena.InternalResultSet.retrieveFirstPage(InternalResultSet.java:61)
com.ibm.team.jfs.rdf.internal.jena.tdb.JenaTdbTxProvider.renderSelect(JenaTdbTxProvider.java:1756)
com.ibm.team.jfs.rdf.internal.jena.tdb.JenaTdbTxProvider.performSelect(JenaTdbTxProvider.java:1510)
com.ibm.team.jfs.rdf.internal.jena.tdb.JenaTdbTxProvider$15.run(JenaTdbTxProvider.java:1626)
com.ibm.team.jfs.rdf.internal.jena.tdb.JenaTdbTxProvider$15.run(JenaTdbTxProvider.java:1)
com.ibm.team.jfs.rdf.internal.jena.tdb.JenaTdbTxProvider.storeOperation(JenaTdbTxProvider.java:196)
First note that the transaction which is concurrently modified is not the same transaction in which the 2 concurrent threads run(!). Second, without too much knowledge about the details of the transaction code, I suspect something is not right somewhere around here in the stacktraces:
com.hp.hpl.jena.tdb.transaction.Transaction.removeIterator(Transaction.java:207)
com.hp.hpl.jena.tdb.transaction.BlockMgrJournal.endIterator(BlockMgrJournal.java:312)
com.hp.hpl.jena.tdb.base.block.BlockMgrWrapper.endIterator(BlockMgrWrapper.java:134)
com.hp.hpl.jena.tdb.base.recordbuffer.RecordRangeIterator.close(RecordRangeIterator.java:155)
com.hp.hpl.jena.tdb.base.recordbuffer.RecordRangeIterator.hasNext(RecordRangeIterator.java:112)
and respectively
com.hp.hpl.jena.tdb.transaction.Transaction.removeIterator(Transaction.java:202)
com.hp.hpl.jena.tdb.transaction.BlockMgrJournal.endIterator(BlockMgrJournal.java:312)
com.hp.hpl.jena.tdb.transaction.BlockMgrJournal.endIterator(BlockMgrJournal.java:313)
com.hp.hpl.jena.tdb.transaction.BlockMgrJournal.endIterator(BlockMgrJournal.java:313)
com.hp.hpl.jena.tdb.base.block.BlockMgrWrapper.endIterator(BlockMgrWrapper.java:134)
com.hp.hpl.jena.tdb.base.recordbuffer.RecordRangeIterator.close(RecordRangeIterator.java:155)
com.hp.hpl.jena.tdb.base.recordbuffer.RecordRangeIterator.hasNext(RecordRangeIterator.java:112)
Hopefully you can make sense of it. The one thing that is 100% is that the IndexOutOfBounds is caused by an attempt to concurrently remove the iterator in this one transaction.
> TxTDB problem during concurrent execution
> -----------------------------------------
>
> Key: JENA-131
> URL: https://issues.apache.org/jira/browse/JENA-131
> Project: Jena
> Issue Type: Bug
> Components: TDB
> Environment: arq-2.8.9-20111001.145524-39 and tx-tdb-0.9.0-20111006.082548-13 on IBM JRE 6
> Reporter: Simon Helsen
> Attachments: patch.txt
>
>
> In a massive concurrent test with many reads and writes, I am running into the problems shown below. I suspect the problem only occurs if a read and write are trying to operate on the same data at the same time, i.e. the transactions don't isolate enough. My test case is inside the framework. I currently have no test case for you to try, but I am hoping you can see something by inspecting the stack trace
> ModelWriteActivity: 1579ms
> 17:46:27,183 [1948218399@qtp-533667791-14] WARN hpl.jena.sparql.engine.iterator.QueryIteratorCheck - Open iterator: QueryIterConcat/55657
> 17:46:27,254 [1948218399@qtp-533667791-14] WARN hpl.jena.sparql.engine.iterator.QueryIteratorCheck - Open iterator: QueryIterSingleton/55658
> 17:46:27,257 [1948218399@qtp-533667791-14] WARN hpl.jena.sparql.engine.iterator.QueryIteratorCheck - Open iterator: QueryIterPeek/55659
> 17:46:27,261 [1948218399@qtp-533667791-14] WARN hpl.jena.sparql.engine.iterator.QueryIteratorCheck - Open iterator: QueryIterTDB/55660
> 17:46:27,264 [1948218399@qtp-533667791-14] WARN hpl.jena.sparql.engine.iterator.QueryIteratorCheck - Open iterator: QueryIterOptionalIndex/55661
> 17:46:27,335 [1948218399@qtp-533667791-14] WARN hpl.jena.sparql.engine.iterator.QueryIteratorCheck - Open iterator: QueryIterOptionalIndex/55662
> 17:46:27,338 [1948218399@qtp-533667791-14] WARN hpl.jena.sparql.engine.iterator.QueryIteratorCheck - Open iterator: QueryIterDefaulting/55803
> 17:46:27,395 [1948218399@qtp-533667791-14] WARN hpl.jena.sparql.engine.iterator.QueryIteratorCheck - Open iterator: QueryIterDefaulting/55807
> 17:46:27,399 [1948218399@qtp-533667791-14] WARN hpl.jena.sparql.engine.iterator.QueryIteratorCheck - Open iterator: QueryIterPeek/55808
> 17:46:27,403 [1948218399@qtp-533667791-14] WARN hpl.jena.sparql.engine.iterator.QueryIteratorCheck - Open iterator: QueryIterTDB/55809
> 17:46:27,406 [1948218399@qtp-533667791-14] WARN hpl.jena.sparql.engine.iterator.QueryIteratorCheck - Open iterator: QueryIterAssign/55810
> 17:46:27,410 [1948218399@qtp-533667791-14] WARN hpl.jena.sparql.engine.iterator.QueryIteratorCheck - Open iterator: QueryIterSingleton/55811
> 17:46:27,490 [1948218399@qtp-533667791-14] WARN hpl.jena.sparql.engine.iterator.QueryIteratorCheck - Open iterator: QueryIterPeek/55812
> 17:46:27,493 [1948218399@qtp-533667791-14] WARN hpl.jena.sparql.engine.iterator.QueryIteratorCheck - Open iterator: QueryIterTDB/55813
> 17:46:27,497 [1948218399@qtp-533667791-14] WARN hpl.jena.sparql.engine.iterator.QueryIteratorCheck - Open iterator: QueryIterOptionalIndex/55814
> 17:46:27,502 [1948218399@qtp-533667791-14] WARN hpl.jena.sparql.engine.iterator.QueryIteratorCheck - Open iterator: QueryIterOptionalIndex/55815
> 17:46:27,507 [1948218399@qtp-533667791-14] ERROR com.ibm.team.jfs - Originating Exception:
> java.lang.IndexOutOfBoundsException: Index: 20, Size: 18
> at java.util.ArrayList.remove(ArrayList.java:552)
> at java.util.ArrayList.remove(ArrayList.java:572)
> at com.hp.hpl.jena.tdb.transaction.Transaction.removeIterator(Transaction.java:188)
> at com.hp.hpl.jena.tdb.transaction.BlockMgrJournal.endIterator(BlockMgrJournal.java:312)
> at com.hp.hpl.jena.tdb.transaction.BlockMgrJournal.endIterator(BlockMgrJournal.java:313)
> at com.hp.hpl.jena.tdb.base.block.BlockMgrWrapper.endIterator(BlockMgrWrapper.java:134)
> at com.hp.hpl.jena.tdb.base.recordbuffer.RecordRangeIterator.close(RecordRangeIterator.java:155)
> at com.hp.hpl.jena.tdb.base.recordbuffer.RecordRangeIterator.hasNext(RecordRangeIterator.java:112)
> at org.openjena.atlas.iterator.Iter$4.hasNext(Iter.java:274)
> at com.hp.hpl.jena.tdb.sys.DatasetControlMRSW$IteratorCheckNotConcurrent.hasNext(DatasetControlMRSW.java:119)
> at org.openjena.atlas.iterator.Iter$3.hasNext(Iter.java:164)
> at org.openjena.atlas.iterator.Iter$6.hasNext(Iter.java:359)
> at org.openjena.atlas.iterator.Iter$3.hasNext(Iter.java:164)
> at org.openjena.atlas.iterator.Iter$4.hasNext(Iter.java:274)
> at org.openjena.atlas.iterator.Iter$3.hasNext(Iter.java:164)
> at org.openjena.atlas.iterator.Iter.hasNext(Iter.java:742)
> at org.openjena.atlas.iterator.RepeatApplyIterator.hasNext(RepeatApplyIterator.java:58)
> at org.openjena.atlas.iterator.RepeatApplyIterator.hasNext(RepeatApplyIterator.java:46)
> at org.openjena.atlas.iterator.RepeatApplyIterator.hasNext(RepeatApplyIterator.java:46)
> at org.openjena.atlas.iterator.RepeatApplyIterator.hasNext(RepeatApplyIterator.java:46)
> at org.openjena.atlas.iterator.RepeatApplyIterator.hasNext(RepeatApplyIterator.java:46)
> at org.openjena.atlas.iterator.Iter$4.hasNext(Iter.java:274)
> at com.hp.hpl.jena.sparql.engine.iterator.QueryIterPlainWrapper.hasNextBinding(QueryIterPlainWrapper.java:54)
> at com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:107)
> at com.hp.hpl.jena.sparql.engine.iterator.QueryIterRepeatApply.makeNextStage(QueryIterRepeatApply.java:106)
> at com.hp.hpl.jena.sparql.engine.iterator.QueryIterRepeatApply.hasNextBinding(QueryIterRepeatApply.java:65)
> at com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:107)
> at com.hp.hpl.jena.sparql.engine.iterator.QueryIterRepeatApply.makeNextStage(QueryIterRepeatApply.java:106)
> at com.hp.hpl.jena.sparql.engine.iterator.QueryIterRepeatApply.hasNextBinding(QueryIterRepeatApply.java:65)
> at com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:107)
> at com.hp.hpl.jena.tdb.solver.OpExecutorTDB.optimizeExecuteQuads(OpExecutorTDB.java:215)
> at com.hp.hpl.jena.tdb.solver.OpExecutorTDB.execute(OpExecutorTDB.java:152)
> at com.hp.hpl.jena.sparql.engine.main.ExecutionDispatch.visit(ExecutionDispatch.java:63)
> at com.hp.hpl.jena.sparql.algebra.op.OpQuadPattern.visit(OpQuadPattern.java:97)
> at com.hp.hpl.jena.sparql.engine.main.ExecutionDispatch.exec(ExecutionDispatch.java:43)
> at com.hp.hpl.jena.sparql.engine.main.OpExecutor.executeOp(OpExecutor.java:119)
> at com.hp.hpl.jena.sparql.engine.main.OpExecutor.execute(OpExecutor.java:208)
> at com.hp.hpl.jena.sparql.engine.main.ExecutionDispatch.visit(ExecutionDispatch.java:105)
> at com.hp.hpl.jena.sparql.algebra.op.OpSequence.visit(OpSequence.java:73)
> at com.hp.hpl.jena.sparql.engine.main.ExecutionDispatch.exec(ExecutionDispatch.java:45)
> at com.hp.hpl.jena.sparql.engine.main.OpExecutor.executeOp(OpExecutor.java:119)
> at com.hp.hpl.jena.sparql.engine.main.OpExecutor.execute(OpExecutor.java:464)
> at com.hp.hpl.jena.sparql.engine.main.ExecutionDispatch.visit(ExecutionDispatch.java:246)
> at com.hp.hpl.jena.sparql.algebra.op.OpAssign.visit(OpAssign.java:116)
> at com.hp.hpl.jena.sparql.engine.main.ExecutionDispatch.exec(ExecutionDispatch.java:45)
> at com.hp.hpl.jena.sparql.engine.main.OpExecutor.executeOp(OpExecutor.java:119)
> at com.hp.hpl.jena.sparql.engine.main.OpExecutor.execute(OpExecutor.java:92)
> at com.hp.hpl.jena.sparql.engine.main.QC.execute(QC.java:52)
> at com.hp.hpl.jena.sparql.engine.main.iterator.QueryIterUnion.nextStage(QueryIterUnion.java:55)
> at com.hp.hpl.jena.sparql.engine.iterator.QueryIterRepeatApply.makeNextStage(QueryIterRepeatApply.java:113)
> at com.hp.hpl.jena.sparql.engine.iterator.QueryIterRepeatApply.hasNextBinding(QueryIterRepeatApply.java:65)
> at com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:107)
> at com.hp.hpl.jena.sparql.engine.iterator.QueryIterConvert.hasNextBinding(QueryIterConvert.java:65)
> at com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:107)
> at com.hp.hpl.jena.sparql.engine.iterator.QueryIterSlice.hasNextBinding(QueryIterSlice.java:76)
> at com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:107)
> at com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorWrapper.hasNextBinding(QueryIteratorWrapper.java:40)
> at com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:107)
> at com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorWrapper.hasNextBinding(QueryIteratorWrapper.java:40)
> at com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:107)
> at com.hp.hpl.jena.sparql.engine.ResultSetStream.hasNext(ResultSetStream.java:70)
> at com.hp.hpl.jena.sparql.engine.QueryExecutionBase.execDescribe(QueryExecutionBase.java:278)
> at com.hp.hpl.jena.sparql.engine.QueryExecutionBase.execDescribe(QueryExecutionBase.java:256)
> <snip>
> DataSetReadActivity: 1249ms
--
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