GH-5294 stack overflow sparql update (#5295)

Author: hmottestad

core/queryalgebra/model/src/main/java/org/eclipse/rdf4j/query/algebra/helpers/collectors/StatementPatternCollector.java

@@ -15,8 +15,10 @@
 import java.util.List;
 
 import org.eclipse.rdf4j.query.algebra.Filter;
+import org.eclipse.rdf4j.query.algebra.Join;
 import org.eclipse.rdf4j.query.algebra.QueryModelNode;
 import org.eclipse.rdf4j.query.algebra.StatementPattern;
+import org.eclipse.rdf4j.query.algebra.TupleExpr;
 import org.eclipse.rdf4j.query.algebra.helpers.AbstractSimpleQueryModelVisitor;
 
 /**
@@ -46,6 +48,37 @@ public void meet(Filter node) {
 		node.getArg().visit(this);
 	}
 
+	@Override
+	public void meet(Join node) throws RuntimeException {
+		TupleExpr leftArg = node.getLeftArg();
+		TupleExpr rightArg = node.getRightArg();
+
+		// INSERT clause is often a deeply nested join. Recursive approach may cause stack overflow. Attempt
+		// non-recursive (or at least less-recursive) approach first.
+		while (true) {
+			if (leftArg instanceof Join && !(rightArg instanceof Join)) {
+				rightArg.visit(this);
+
+				Join join = (Join) leftArg;
+				leftArg = join.getLeftArg();
+				rightArg = join.getRightArg();
+
+			} else if (rightArg instanceof Join && !(leftArg instanceof Join)) {
+				leftArg.visit(this);
+
+				Join join = (Join) rightArg;
+				leftArg = join.getLeftArg();
+				rightArg = join.getRightArg();
+
+			} else {
+				leftArg.visit(this);
+				rightArg.visit(this);
+				return;
+			}
+		}
+
+	}
+
 	@Override
 	public void meet(StatementPattern node) {
 		statementPatterns.add(node);

core/sail/memory/src/test/java/org/eclipse/rdf4j/sail/memory/MemoryStoreConnectionTest.java

@@ -10,15 +10,47 @@
  *******************************************************************************/
 package org.eclipse.rdf4j.sail.memory;
 
+import static org.assertj.core.api.Assertions.assertThat;
+
 import java.io.File;
 
+import org.eclipse.rdf4j.common.transaction.IsolationLevels;
+import org.eclipse.rdf4j.model.IRI;
+import org.eclipse.rdf4j.model.vocabulary.RDF;
 import org.eclipse.rdf4j.repository.Repository;
 import org.eclipse.rdf4j.repository.sail.SailRepository;
 import org.eclipse.rdf4j.testsuite.repository.RepositoryConnectionTest;
+import org.junit.jupiter.api.Test;
 
 public class MemoryStoreConnectionTest extends RepositoryConnectionTest {
 	@Override
 	protected Repository createRepository(File dataDir) {
 		return new SailRepository(new MemoryStore());
 	}
+
+	@Test
+	public void reallyBigUpdateToTriggerPotentialStackOverflowTest() {
+		setupTest(IsolationLevels.NONE);
+
+		IRI g1 = vf.createIRI("urn:test:g1");
+		testCon.begin();
+		testCon.add(vf.createBNode(), RDF.TYPE, g1);
+		testCon.commit();
+
+		testCon.begin();
+
+		StringBuilder bigUpdate = new StringBuilder();
+		bigUpdate.append("DELETE { ?s ?p ?o } INSERT{\n");
+
+		for (int i = 0; i < 20000; i++) {
+			bigUpdate.append(" [] <urn:test:prop> \"").append(i).append("\".\n");
+		}
+		bigUpdate.append("\n} WHERE { ?s ?p ?o }");
+
+		testCon.prepareUpdate(bigUpdate.toString()).execute();
+
+		long size = testCon.size();
+		assertThat(size).isEqualTo(20000);
+		testCon.commit();
+	}
 }