LorenzBuehmann opened a new issue, #1634:
URL: https://github.com/apache/jena/issues/1634
### Version
4.7.0-SNAPSHOT
### What happened?
Dataset: some DBpedia stuff
Query ("give me longest river"):
``` sparql
SELECT DISTINCT ?uri WHERE {
?uri a <http://dbpedia.org/ontology/River>
{
?uri <http://dbpedia.org/ontology/length> ?l
} UNION {
?uri <http://dbpedia.org/property/length> ?l
}
}
ORDER BY DESC(?l) OFFSET 0 LIMIT 1
```
it fails with 500 and "Comparison method violates its general contract!".
DBpedia data is annoying anyways, there are plenty of length literals with
different datatype. For debugging I reduced the literal mix to two
:`xsd:double, <http://dbpedia.org/datatype/kilometre>`
``` sparql
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
SELECT DISTINCT ?uri WHERE {
?uri a <http://dbpedia.org/ontology/River>
{
?uri <http://dbpedia.org/ontology/length> ?l
} UNION {
?uri <http://dbpedia.org/property/length> ?l
}
filter(datatype(?l) in (xsd:double,
<http://dbpedia.org/datatype/kilometre>))
}
ORDER BY DESC(?l) OFFSET 0 LIMIT 1
```
which still fails.
It does not fail if we project/select the length literal `?l` though:
```sparql
SELECT DISTINCT ?uri ?l WHERE {
?uri a <http://dbpedia.org/ontology/River>
{
?uri <http://dbpedia.org/ontology/length> ?l
} UNION {
?uri <http://dbpedia.org/property/length> ?l
}
filter(datatype(?l) in (xsd:double,
<http://dbpedia.org/datatype/kilometre>))
}
ORDER BY DESC(?l) OFFSET 0 LIMIT 1
```
Looking for the Java exception I found source like here:
https://bugs.openjdk.org/browse/JDK-8234482
which also does contain a hint that timsort needs sufficient amount of data
to fail:
> TimSort doesn't throw this exception in all cases, though, only if there
are a sufficiently large number of elements to be merged (generally > 32
elements, often hundreds are required), and if the sorting algorithm happens to
detect an contradiction in the comparison method.
### Relevant output and stacktrace
```shell
Query = PREFIX xsd: <http://www.w3.org/2001/XMLSchema#> SELECT DISTINCT
?uri WHERE { ?uri a <http://dbpedia.org/ontology/River> { ?uri
<http://dbpedia.org/ontology/length> ?l } UNION { ?uri
<http://dbpedia.org/property/length> ?l } filter(datatype(?l) in
(xsd:double, <http://dbpedia.org/datatype/kilometre>)) } ORDER BY DESC(?l)
OFFSET 0 LIMIT 1
10:12:42 WARN Fuseki :: [32] RC = 500 : Comparison method violates
its general contract!
java.lang.IllegalArgumentException: Comparison method violates its general
contract!
at java.util.TimSort.mergeHi(TimSort.java:903) ~[?:?]
at java.util.TimSort.mergeAt(TimSort.java:520) ~[?:?]
at java.util.TimSort.mergeCollapse(TimSort.java:448) ~[?:?]
at java.util.TimSort.sort(TimSort.java:245) ~[?:?]
at java.util.Arrays.sort(Arrays.java:1441) ~[?:?]
at
org.apache.jena.atlas.data.AbortableComparator.abortableSort(AbortableComparator.java:57)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.atlas.data.SortedDataBag.iterator(SortedDataBag.java:205)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.atlas.data.SortedDataBag.iterator(SortedDataBag.java:192)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.sparql.engine.iterator.QueryIterSort$SortedBindingIterator.initializeIterator(QueryIterSort.java:88)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.atlas.iterator.IteratorDelayedInitialization.init(IteratorDelayedInitialization.java:38)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.atlas.iterator.IteratorDelayedInitialization.hasNext(IteratorDelayedInitialization.java:48)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.sparql.engine.iterator.QueryIterPlainWrapper.hasNextBinding(QueryIterPlainWrapper.java:59)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:116)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.sparql.engine.iterator.QueryIterConvert.hasNextBinding(QueryIterConvert.java:58)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:116)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.sparql.engine.iterator.QueryIterDistinct.getInputNextUnseen(QueryIterDistinct.java:113)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.sparql.engine.iterator.QueryIterDistinct.hasNextBinding(QueryIterDistinct.java:72)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:116)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.sparql.engine.iterator.QueryIterSlice.hasNextBinding(QueryIterSlice.java:76)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:116)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.sparql.engine.iterator.QueryIteratorWrapper.hasNextBinding(QueryIteratorWrapper.java:38)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:116)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.sparql.engine.iterator.QueryIteratorWrapper.hasNextBinding(QueryIteratorWrapper.java:38)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:116)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.sparql.exec.RowSetStream.hasNext(RowSetStream.java:47)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.sparql.engine.ResultSetStream.hasNext(ResultSetStream.java:81)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.fuseki.servlets.SPARQLQueryProcessor.executeQuery(SPARQLQueryProcessor.java:380)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.fuseki.servlets.SPARQLQueryProcessor.execute(SPARQLQueryProcessor.java:279)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.fuseki.servlets.SPARQLQueryProcessor.executeWithParameter(SPARQLQueryProcessor.java:224)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.fuseki.servlets.SPARQLQueryProcessor.execute(SPARQLQueryProcessor.java:209)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.fuseki.servlets.ActionService.executeLifecycle(ActionService.java:58)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.fuseki.servlets.SPARQLQueryProcessor.execPost(SPARQLQueryProcessor.java:84)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.fuseki.servlets.ActionProcessor.process(ActionProcessor.java:34)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.fuseki.servlets.ActionBase.process(ActionBase.java:54)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.fuseki.servlets.ActionExecLib.execActionSub(ActionExecLib.java:124)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.fuseki.servlets.ActionExecLib.execAction(ActionExecLib.java:98)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.fuseki.server.Dispatcher.dispatchAction(Dispatcher.java:164)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.fuseki.server.Dispatcher.process(Dispatcher.java:156)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
at
org.apache.jena.fuseki.server.Dispatcher.dispatch(Dispatcher.java:83)
~[fuseki-server.jar:4.7.0-SNAPSHOT]
```
### Are you interested in making a pull request?
_No response_
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