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https://issues.apache.org/jira/browse/JENA-2310?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Lorenz Bühmann updated JENA-2310:
---------------------------------
Environment: (was: {code:java}
// code placeholder
{code}
{code:java}
// Some comments here
public String getFoo()
{
return foo;
}
{code})
> NPE with geospatial property function due to query rewrite index issue
> ----------------------------------------------------------------------
>
> Key: JENA-2310
> URL: https://issues.apache.org/jira/browse/JENA-2310
> Project: Apache Jena
> Issue Type: Bug
> Components: GeoSPARQL
> Affects Versions: Jena 4.4.0
> Reporter: Lorenz Bühmann
> Priority: Major
>
> Using a GeoSPARQL query with a geospatial property function, e.g.
> {code:java}
> SELECT * {
> :x geo:hasGeometry ?geo1 .
> ?s2 geo:hasGeometry ?geo2 .
> ?geo1 geo:sfContains ?geo2
> }{code}
> leads to an nondeterministic NPE when we're doing this query a a larger
> dataset.
> The reason is explained here:
> - evaluation of the property function leads to {{GenericPropertyFunction}}
> class with
> {code:java}
> private QueryIterator bothBound(Binding binding, Node subject, Node
> predicate, Node object, ExecutionContext execCxt) {
> Graph graph = execCxt.getActiveGraph();
> QueryRewriteIndex queryRewriteIndex =
> QueryRewriteIndex.retrieve(execCxt);
> Boolean isPositiveResult = queryRewrite(graph, subject, predicate,
> object, queryRewriteIndex);
> if (isPositiveResult) {
> {code}
>
> which leads to the query rewrite part and in {{QueryRewriteIndex}} class we
> have
> {code:java}
> if (index.containsKey(key)) {
> result = index.get(key);
> } else {
> result = propertyFunction.testFilterFunction(subjectGeometryLiteral,
> objectGeometryLiteral);
> index.put(key, result);
> }
> {code}
> {{index}} is an {{ExpiringMap}} which extends {{ConcurrentHashMap}} with an
> additional {{TimerTask}} clearing the map periodically - and this is why we
> get an NPE sometimes. Have a look at the lines above, in particular
> {code:java}
> if (index.containsKey(key)){
> result = index.get(key);
> }
> {code}
> that part isn't atomic, thus, while {{containsKey}} could be true, the
> {{TimerTask}} might clear the map before we go to get - this will lead to a
> {{null}} value returned which will lead to an NPE in the check
> Since Java 8 the atomic way is to use {{computeIfAbsent}}, i.e. we can do
> {code:java}
> Boolean result = index.computeIfAbsent(key, k ->
> propertyFunction.testFilterFunction(subjectGeometryLiteral,
> objectGeometryLiteral));{code}
>
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