Hi
I consistently get a NullPointerException from this query on my test TDB
on laptop.
SELECT DISTINCT ?thing
WHERE {
graph ?thing {
[] ?p ?O .
}
} LIMIT 200
Looking into code : BindingBase.java line 203 , it appears that a binding's
node is null for one SELECT result.
This binding stands for a named graph.
So the database is probably broken. Of course, this is a work and test
database whose content has no value, but I try to understand and prevent
this to happen on production database.
Is a there a bug somewhere ?
What is the likely cause ? During tests and debugs, transactions may have
not been rolled back , application was killed, etc .
How could the database be repaired in such cases ? By doing a tdbdump and
recreate the TDB ?
Running on Jena 3.6.0 and Ubuntu 2017.10 and java version "1.8.0_121" .
java.lang.NullPointerException
at
org.apache.jena.sparql.engine.binding.BindingBase.hashCode(BindingBase.java:203)
at
org.apache.jena.sparql.engine.binding.BindingBase.hashCode(BindingBase.java:183)
at java.util.HashMap.hash(HashMap.java:338)
at java.util.HashMap.containsKey(HashMap.java:595)
at java.util.HashSet.contains(HashSet.java:203)
at
org.apache.jena.sparql.engine.iterator.QueryIterDistinct.getInputNextUnseen(QueryIterDistinct.java:106)
at
org.apache.jena.sparql.engine.iterator.QueryIterDistinct.hasNextBinding(QueryIterDistinct.java:70)
at
org.apache.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:114)
at
org.apache.jena.sparql.engine.iterator.QueryIterSlice.hasNextBinding(QueryIterSlice.java:76)
at
org.apache.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:114)
at
org.apache.jena.sparql.engine.iterator.QueryIteratorWrapper.hasNextBinding(QueryIteratorWrapper.java:39)
at
org.apache.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:114)
at
org.apache.jena.sparql.engine.iterator.QueryIteratorWrapper.hasNextBinding(QueryIteratorWrapper.java:39)
at
org.apache.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:114)
at
org.apache.jena.sparql.engine.iterator.QueryIteratorWrapper.hasNextBinding(QueryIteratorWrapper.java:39)
at
org.apache.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:114)
at
org.apache.jena.sparql.engine.ResultSetStream.hasNext(ResultSetStream.java:74)
* at
org.apache.jena.sparql.engine.ResultSetCheckCondition.hasNext(ResultSetCheckCondition.java:55)*
at
scala.collection.convert.Wrappers$JIteratorWrapper.hasNext(Wrappers.scala:42)
at scala.collection.Iterator$class.toStream(Iterator.scala:1320)
at scala.collection.AbstractIterator.toStream(Iterator.scala:1334)
at
scala.collection.Iterator$$anonfun$toStream$1.apply(Iterator.scala:1320)
at
scala.collection.Iterator$$anonfun$toStream$1.apply(Iterator.scala:1320)
at scala.collection.immutable.Stream$Cons.tail(Stream.scala:1233)
at scala.collection.immutable.Stream$Cons.tail(Stream.scala:1223)
at
scala.collection.immutable.Stream$$anonfun$map$1.apply(Stream.scala:418)
at
scala.collection.immutable.Stream$$anonfun$map$1.apply(Stream.scala:418)
at scala.collection.immutable.Stream$Cons.tail(Stream.scala:1233)
at scala.collection.immutable.Stream$Cons.tail(Stream.scala:1223)
at scala.collection.generic.Growable$class.loop$1(Growable.scala:54)
at
scala.collection.generic.Growable$class.$plus$plus$eq(Growable.scala:57)
at
scala.collection.mutable.ListBuffer.$plus$plus$eq(ListBuffer.scala:183)
at
scala.collection.mutable.ListBuffer.$plus$plus$eq(ListBuffer.scala:45)
at scala.collection.TraversableLike$class.to(TraversableLike.scala:590)
at scala.collection.AbstractTraversable.to(Traversable.scala:104)
at
deductions.runtime.sparql_cache.SPARQLHelpers$$anonfun$sparqlSelectQueryVariablesNT$1.apply(SPARQLHelpers.scala:426)
--
Jean-Marc Vanel
http://www.semantic-forms.cc:9111/display?displayuri=http://jmvanel.free.fr/jmv.rdf%23me#subject
<http://www.semantic-forms.cc:9111/display?displayuri=http://jmvanel.free.fr/jmv.rdf%23me>
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