(sorry - I'm bandwidth reduced ATM - connected by phone)
Putting in an empty default graph would be better. A dataset always has
a default graph which is why the code assumes it's not null.
If the DatasetImpl.setDefaultModel is fixed, are there any other barriers?
While null isn't a good idea, the code can be made more robust. But by
probability there will be other code that does not check for null as it
shouldn't be.
One fix is to have setDefaultModel add an empty (immutable) model.
The bit I don't quite understand here is that things only get converted
to quads for TDB and the default graph is fixed so I don't see the
connection with setDefaultModel.
You can have concurrent queries - Fuseki does all the time. Either the
right MRSW lock or transactions will work. (Fuseki uses transactions
always - for in-memory it creates an associated transactional control
object).
Andy
On 14/07/13 18:12, Reto Bachmann-Gmür wrote:
Hi Minto
I'm sorry for having introduced this problem. I just noticed that
BaseTdbTcProvider completely ignored the specified default graph. Not
sure what I thought exacly setting it to null. I guess it was the
incomplete ste of setting it to the actually wanted default graph.
The problem is that by the jena design we would need to prevent
concurrent queries with different default graphs. So I think it might
be better to add a FROM-clause to the query if the query doesn't
already has one. This would require again some parsing. The preparser
seems to be the place to do this. WDYT, can we do a solution that
actually provided support for the specified default graph or should we
first just provide a release that ignores it without NPE?
Cheers,
Reto
On Sun, Jul 14, 2013 at 11:58 AM, Minto van der Sluis <[email protected]> wrote:
Hi Reto,
If I am correct the NPE I discovered will always happens for fastlaned
queries on Jena TDB based TcProviders due to the following line present
in BaseTdbTcProvider.java:
getDataset().setDefaultModel(null);
The NPE can be clearly seen in DatasetImpl if model is null:
@Override
public void setDefaultModel(Model model)
{
// Assumes single writer.
removeFromCache(dsg.getDefaultGraph()) ;
addToCache(model) ;
dsg.setDefaultGraph(model.getGraph()) ;
}
Did you have anything special in mind when you added the null model?
Regards,
Minto
Op 12-7-2013 23:50, Reto Bachmann-Gmür schreef:
Thanks Minto. I would rather not withdraw the release candidate but
have a new release very soon (max a couple of weeks).
Reto
On Fri, Jul 12, 2013 at 10:48 PM, Minto van der Sluis <[email protected]> wrote:
Fixed this with commit r1502677 (CLEREZZA-802)
Please have a close look. Might need to be part of the pending release
as well.
Regards,
Minto
Op 12-7-2013 18:14, Minto van der Sluis schreef:
This time I end up with an NPE, see stack below.
My changes resulted in the following
public Object executeSparqlQuery(String query, TripleCollection
defaultGraph, boolean forceFastlane) throws ParseException {
TcProvider singleTargetTcProvider = null;
if (forceFastlane) {
singleTargetTcProvider = getSingleTargetTcProvider();
} else {
final UriRef defaultGraphName = new
UriRef("urn:x-temp:/kjsfadfhfasdffds");
SparqlPreParser sparqlPreParser = new SparqlPreParser(this);
final Set<UriRef> referencedGraphs =
sparqlPreParser.getReferredGraphs(query, defaultGraphName);
if ((referencedGraphs != null) &&
(!referencedGraphs.contains(defaultGraphName))) {
singleTargetTcProvider =
getSingleTargetTcProvider(referencedGraphs);
}
}
if ((singleTargetTcProvider != null) && (singleTargetTcProvider
instanceof QueryableTcProvider)) {
return
((QueryableTcProvider)singleTargetTcProvider).executeSparqlQuery(query,
null);
}
final QueryEngine queryEngine = this.queryEngine;
if (queryEngine != null) {
return queryEngine.execute(this, defaultGraph, query);
} else {
throw new NoQueryEngineException();
}
}
private TcProvider getSingleTargetTcProvider() {
return providerList.first();
}
I guess the following like in BaseTdbTcProvider.executeSparqlQuery() is
the culprit:
getDataset().setDefaultModel(null);
Stacktrace:
java.lang.NullPointerException
at
com.hp.hpl.jena.sparql.core.DatasetImpl.addToCache(DatasetImpl.java:259)
at
com.hp.hpl.jena.sparql.core.DatasetImpl.setDefaultModel(DatasetImpl.java:214)
at
org.apache.clerezza.rdf.jena.tdb.storage.BaseTdbTcProvider.executeSparqlQuery(BaseTdbTcProvider.java:39)
at
org.apache.clerezza.rdf.jena.tdb.storage.ScalableSingleTdbDatasetTcProvider.executeSparqlQuery(ScalableSingleTdbDatasetTcProvider.java:81)
at
org.apache.clerezza.rdf.core.access.TcManager.executeSparqlQuery(TcManager.java:310)
at
org.apache.clerezza.rdf.core.access.TcManager.executeSparqlQuery(TcManager.java:282)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native
Method)[:1.7.0_17]
at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)[:1.7.0_17]
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)[:1.7.0_17]
at java.lang.reflect.Method.invoke(Method.java:601)[:1.7.0_17]
at
org.apache.aries.proxy.impl.ProxyHandler$1.invoke(ProxyHandler.java:54)[12:org.apache.aries.proxy.impl:1.0.0]
at
org.apache.aries.proxy.impl.ProxyHandler.invoke(ProxyHandler.java:119)[12:org.apache.aries.proxy.impl:1.0.0]
at
org.apache.clerezza.rdf.core.access.$TcManager10360330.executeSparqlQuery(Unknown
Source)[181:org.apache.clerezza.rdf.core:0.13.0.SNAPSHOT]
at
nl.overheid.stelsel.digimelding.astore.storage.clerezza.ClerezzaStorageProvider.query(ClerezzaStorageProvider.java:250)[209:astore-storage-clerezza:0.7.0.SNAPSHOT]
--
ir. ing. Minto van der Sluis
Software innovator / renovator
Xup BV
Mobiel: +31 (0) 626 014541
--
ir. ing. Minto van der Sluis
Software innovator / renovator
Xup BV
Mobiel: +31 (0) 626 014541
