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Posted to dev@jena.apache.org by "Andy Seaborne (JIRA)" <ji...@apache.org> on 2013/09/26 12:18:06 UTC
[jira] [Updated] (JENA-506) SPARQL "ORDER BY RAND()" may lead to a
"Comparison method violates its general contract!" exception
[ https://issues.apache.org/jira/browse/JENA-506?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Andy Seaborne updated JENA-506:
-------------------------------
Priority: Major (was: Critical)
> SPARQL "ORDER BY RAND()" may lead to a "Comparison method violates its general contract!" exception
> ----------------------------------------------------------------------------------------------------
>
> Key: JENA-506
> URL: https://issues.apache.org/jira/browse/JENA-506
> Project: Apache Jena
> Issue Type: Bug
> Components: ARQ
> Affects Versions: Jena 2.10.1
> Environment: OpenJDK 1.7.0_21 (64)
> Reporter: Pasquale Minervini
>
> It seems like the SPARQL "SELECT [..] ORDER BY RAND()" query construct can cause troubles when retrieving results; here's a complete stacktrace (Specifically, I've been querying the DBLP RDF dataset: http://sw.deri.org/~aharth/2004/07/dblp/). I think the construct can be quite useful for randomly sampling nodes from the RDF graph, that's the reason for the 'Critical'.
> ARQ: VERSION: 2.10.1
> ARQ: BUILD_DATE: 2013-05-11T22:05:51+0100
> Exception in thread "main" java.lang.IllegalArgumentException: Comparison method violates its general contract!
> at java.util.TimSort.mergeLo(TimSort.java:747)
> at java.util.TimSort.mergeAt(TimSort.java:483)
> at java.util.TimSort.mergeCollapse(TimSort.java:408)
> at java.util.TimSort.sort(TimSort.java:214)
> at java.util.TimSort.sort(TimSort.java:173)
> at java.util.Arrays.sort(Arrays.java:659)
> at org.apache.jena.atlas.data.SortedDataBag.iterator(SortedDataBag.java:204)
> at org.apache.jena.atlas.data.SortedDataBag.iterator(SortedDataBag.java:189)
> at com.hp.hpl.jena.sparql.engine.iterator.QueryIterSort$SortedBindingIterator.initializeIterator(QueryIterSort.java:99)
> at org.apache.jena.atlas.iterator.IteratorDelayedInitialization.init(IteratorDelayedInitialization.java:40)
> at org.apache.jena.atlas.iterator.IteratorDelayedInitialization.hasNext(IteratorDelayedInitialization.java:50)
> 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:112)
> 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:112)
> 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:112)
> 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:112)
> at com.hp.hpl.jena.sparql.engine.ResultSetStream.hasNext(ResultSetStream.java:75)
> I can easily provide a snippet if you really need it.
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