rvesse commented on a change in pull request #580: JENA-1719: Work around for
iterators being held across transactions
URL: https://github.com/apache/jena/pull/580#discussion_r298948482
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File path:
jena-core/src/main/java/org/apache/jena/reasoner/rulesys/impl/SafeTripleIterator.java
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@@ -0,0 +1,56 @@
+package org.apache.jena.reasoner.rulesys.impl;
+
+import org.apache.jena.graph.Triple;
+import org.apache.jena.reasoner.TriplePattern;
+import org.apache.jena.reasoner.rulesys.BackwardRuleInfGraphI;
+import org.apache.jena.util.iterator.ClosableIterator;
+import org.apache.jena.util.iterator.ExtendedIterator;
+
+/**
+ * Wrapper around triple searches using in the back chainer to attempt a
restart
+ * in the case of a failure such as cross-transaction query.
+ */
+public class SafeTripleIterator implements ClosableIterator<Triple> {
+
+ protected ExtendedIterator<Triple> matchIterator;
+ protected long offset = 0;
+ protected TriplePattern goal;
+ protected BackwardRuleInfGraphI infGraph;
+
+ public SafeTripleIterator(LPInterpreter interpreter, TriplePattern goal) {
+ this.infGraph = interpreter.getEngine().getInfGraph();
+ this.goal = goal;
+ restart();
+ }
+
+ protected void restart() {
+ matchIterator = infGraph.findDataMatches(goal);
+ for (int i = 0; i < offset; i++) matchIterator.next();
Review comment:
For the case of `restart()` under `next()` this is fine but for `restart()`
under `hasNext()` you'd expect to get a `false` return not an exception
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