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https://issues.apache.org/jira/browse/JENA-1857?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17056106#comment-17056106
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Andy Seaborne commented on JENA-1857:
-------------------------------------
The information is there and works inside transactions, sometimes outside.
In {{QuadTableForm}}, on the fast path for listGraphNodes, {{local().get()}} is
null outside a transaction.
{{Txn.executeRead(dsg, ()->{});}} after {{dsg.add(q)}} works.
But a W transaction does not.
{code:java}
dsg.add(q);
Txn.executeWrite(dsg, ()->{});
System.out.println(dsg.size());
{code}
A fix might be:
{code:java}
@Override
public Stream<Node> listGraphNodes() {
FourTupleMap x = local().get();
if ( x == null )
x = master().get();
return x.entryStream().map(Entry::getKey);
}
{code}
but it touches two volatiles/AtomicReferences. I _think_ if it is local() then
master() it is thread safe transactionally. If non-transactional access is
going on, "doesn't crash" is all we can guarantee and IIUC {{master().get()}}
is never null.
> DatasetGraphInMemory.listGraphNodes causes exception outside a transaction
> --------------------------------------------------------------------------
>
> Key: JENA-1857
> URL: https://issues.apache.org/jira/browse/JENA-1857
> Project: Apache Jena
> Issue Type: Task
> Components: TIM
> Affects Versions: Jena 3.14.0
> Reporter: Andy Seaborne
> Priority: Major
>
> Test case:
> {code:java}
> public static void main(String ... a) {
> DatasetGraph dsg = DatasetGraphFactory.createTxnMem();
> Quad q = SSE.parseQuad("(:g :s :p :o)");
> dsg.add(q);
> try {
> System.out.println(dsg.size());
> } catch (Exception ex) {
> ex.printStackTrace();
> }
> }
> {code}
>
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