Possible bug with aggregates and fts (solr) search.

[nguyenm100]

Current Behavior

Putting this out early in case in jogs anyone's memory. I don't have a solid case right now but will update as we go. But running this query sometimes produces an error (works other times so not sure if it's data related). Any tips on how or where to debug would be grateful.

PREFIX search: <http://www.openrdf.org/contrib/lucenesail#>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX skos:  <http://www.w3.org/2004/02/skos/core#>
prefix owl: <http://www.w3.org/2002/07/owl#>

SELECT ?subj (MAX(?score) as ?score) ?definition ?label ?type ?graph WHERE {
  VALUES ?graph { /* bunch of graph iris */ }

  GRAPH ?graph {
    ?subj search:matches [
      search:score ?score ;
      search:property rdfs:label ;
      search:snippet ?snippet ;
      search:query "*debu*" ;
    ]

    optional {
      ?subj skos:definition ?definition .
    }

    optional {
      ?subj skos:prefLabel ?label .
    }

    optional {
      ?subj rdfs:isDefinedBy ?modelIRI .
    }

    ?subj rdf:type ?type .
  }
}
GROUP BY ?subj ?label ?type ?definition ?graph
ORDER BY DESC(?score)

(sometimes) gives the stack:

requestId=04b77fb7-8153-4233-bfab-49b22275b37c Query evaluation exception caught
org.eclipse.rdf4j.query.QueryEvaluationException: Unsupported value expr type: class org.eclipse.rdf4j.query.algebra.Max
	at org.eclipse.rdf4j.query.algebra.evaluation.impl.DefaultEvaluationStrategy.precompile(DefaultEvaluationStrategy.java:907)
	at org.eclipse.rdf4j.query.algebra.evaluation.optimizer.ConstantOptimizer$ConstantVisitor.meetUnaryValueOperator(ConstantOptimizer.java:228)
	at org.eclipse.rdf4j.query.algebra.helpers.AbstractSimpleQueryModelVisitor.meet(AbstractSimpleQueryModelVisitor.java:364)
	at org.eclipse.rdf4j.query.algebra.Max.visit(Max.java:28)
	at org.eclipse.rdf4j.query.algebra.GroupElem.visitChildren(GroupElem.java:69)
	at org.eclipse.rdf4j.query.algebra.helpers.AbstractSimpleQueryModelVisitor.meet(AbstractSimpleQueryModelVisitor.java:269)
	at org.eclipse.rdf4j.query.algebra.GroupElem.visit(GroupElem.java:64)
	at org.eclipse.rdf4j.query.algebra.Group.visitChildren(Group.java:141)
	at org.eclipse.rdf4j.query.algebra.helpers.AbstractSimpleQueryModelVisitor.meetUnaryTupleOperator(AbstractSimpleQueryModelVisitor.java:595)
	at org.eclipse.rdf4j.query.algebra.helpers.AbstractSimpleQueryModelVisitor.meet(AbstractSimpleQueryModelVisitor.java:259)
	at org.eclipse.rdf4j.query.algebra.Group.visit(Group.java:133)
	at org.eclipse.rdf4j.query.algebra.UnaryTupleOperator.visitChildren(UnaryTupleOperator.java:72)
	at org.eclipse.rdf4j.query.algebra.Extension.visitChildren(Extension.java:99)
	at org.eclipse.rdf4j.query.algebra.helpers.AbstractSimpleQueryModelVisitor.meetUnaryTupleOperator(AbstractSimpleQueryModelVisitor.java:595)
	at org.eclipse.rdf4j.query.algebra.helpers.AbstractSimpleQueryModelVisitor.meet(AbstractSimpleQueryModelVisitor.java:234)
	at org.eclipse.rdf4j.query.algebra.Extension.visit(Extension.java:94)
	at org.eclipse.rdf4j.query.algebra.UnaryTupleOperator.visitChildren(UnaryTupleOperator.java:72)
	at org.eclipse.rdf4j.query.algebra.Order.visitChildren(Order.java:90)
	at org.eclipse.rdf4j.query.algebra.helpers.AbstractSimpleQueryModelVisitor.meetUnaryTupleOperator(AbstractSimpleQueryModelVisitor.java:595)
	at org.eclipse.rdf4j.query.algebra.helpers.AbstractSimpleQueryModelVisitor.meet(AbstractSimpleQueryModelVisitor.java:404)
	at org.eclipse.rdf4j.query.algebra.Order.visit(Order.java:81)
	at org.eclipse.rdf4j.query.algebra.UnaryTupleOperator.visitChildren(UnaryTupleOperator.java:72)
	at org.eclipse.rdf4j.query.algebra.Projection.visitChildren(Projection.java:86)
	at org.eclipse.rdf4j.query.algebra.helpers.AbstractSimpleQueryModelVisitor.meetUnaryTupleOperator(AbstractSimpleQueryModelVisitor.java:595)
	at org.eclipse.rdf4j.query.algebra.helpers.AbstractSimpleQueryModelVisitor.meet(AbstractSimpleQueryModelVisitor.java:414)
	at org.eclipse.rdf4j.query.algebra.Projection.visit(Projection.java:80)
	at org.eclipse.rdf4j.query.algebra.UnaryTupleOperator.visitChildren(UnaryTupleOperator.java:72)
	at org.eclipse.rdf4j.query.algebra.helpers.AbstractSimpleQueryModelVisitor.meet(AbstractSimpleQueryModelVisitor.java:430)
	at org.eclipse.rdf4j.query.algebra.QueryRoot.visit(QueryRoot.java:41)
	at org.eclipse.rdf4j.query.algebra.evaluation.optimizer.ConstantOptimizer.optimize(ConstantOptimizer.java:77)
	at org.eclipse.rdf4j.query.algebra.evaluation.impl.DefaultEvaluationStrategy.optimize(DefaultEvaluationStrategy.java:330)
	at org.eclipse.rdf4j.sail.base.SailSourceConnection.evaluateInternal(SailSourceConnection.java:251)
	at org.eclipse.rdf4j.sail.lmdb.LmdbStoreConnection.evaluateInternal(LmdbStoreConnection.java:137)
	at org.eclipse.rdf4j.sail.helpers.AbstractSailConnection.evaluate(AbstractSailConnection.java:333)
	at org.eclipse.rdf4j.sail.helpers.SailConnectionWrapper.evaluate(SailConnectionWrapper.java:115)
	/* SNIP */
	at org.eclipse.rdf4j.sail.helpers.AbstractSailConnection.evaluate(AbstractSailConnection.java:333)
	at org.eclipse.rdf4j.sail.helpers.SailConnectionWrapper.evaluate(SailConnectionWrapper.java:115)
	at org.eclipse.rdf4j.sail.lucene.LuceneSailConnection.evaluateInternal(LuceneSailConnection.java:473)
	at org.eclipse.rdf4j.sail.lucene.LuceneSailConnection.evaluate(LuceneSailConnection.java:406)
	at org.eclipse.rdf4j.repository.sail.SailTupleQuery.evaluate(SailTupleQuery.java:52)
	at org.eclipse.rdf4j.http.server.repository.handler.DefaultQueryRequestHandler.evaluateQuery(DefaultQueryRequestHandler.java:102)
	at org.eclipse.rdf4j.http.server.repository.handler.DefaultQueryRequestHandler.evaluateQuery(DefaultQueryRequestHandler.java:81)
	at org.eclipse.rdf4j.http.server.repository.handler.AbstractQueryRequestHandler.handleQueryRequest(AbstractQueryRequestHandler.java:82)
	at org.eclipse.rdf4j.http.server.repository.AbstractRepositoryController.handleRequestInternal(AbstractRepositoryController.java:53)
	at org.springframework.web.servlet.mvc.AbstractController.handleRequest(AbstractController.java:177)
	at org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:51)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1072)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:965)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
	at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:681)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:764)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
	at com.github.ziplet.filter.compression.CompressingFilter.doFilter(CompressingFilter.java:263)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:197)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:135)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
	at org.apache.catalina.valves.HealthCheckValve.invoke(HealthCheckValve.java:102)
	at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:687)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:360)
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:399)
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:890)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1787)
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
	at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
	at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.base/java.lang.Thread.run(Thread.java:840)

Expected Behavior

no error

Steps To Reproduce

will try and find a repro case.

Version

5.0.3

Are you interested in contributing a solution yourself?

Perhaps?

Anything else?

No response

[hmottestad]

ConstantOptimizer seems to encounter a MAX(...) function and thinks it's a constant. Not sure why, but might be that you are adding something invalid inside the VALUES clause. That would be my first guess.

[hmottestad]

You also have (MAX(?score) as ?score). Might be better to use two different variables. Maybe the constant optimizer is able to optimise the ?score variable, but doesn't know what to do when the variable is used on both sides of an effective bind.

[nguyenm100]

what's odd is that it only happens some times. one of my guys just stripped out everything in the sparql but the original select, search query, and group and ran it repeatedly 200 times and it happened on the 92nd call. race condition and/or state bug would be my guess. will see if we can repo off local lucene instead of solr.

[hmottestad]

Still happening when you remove the max() function or when you use two different variable names in the projection?

[odysa]

I tried `(MAX(?score) as ?score1). This issue still happened.

PREFIX search: <http://www.openrdf.org/contrib/lucenesail#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>

SELECT ?subj (MAX(?score) as ?scoreabcd)
  WHERE {
  ?subj search:matches [
	      search:query "*Inti*";
	      search:property rdfs:label;
	      search:score ?score;
	      search:snippet ?snippet
     ]
}
GROUP BY ?subj

I am trying to create a minimal reproducible example.

[odysa]

Hello @hmottestad, I am able to reproduce it.

1. Use MAX or MIN in the search query
2. Use TupleFunctionEvaluationMode.NATIVE or TupleFunctionEvaluationMode.SERVICE. But using TRIPLE_SOURCE is ok
3. There's only 1 triple in the result. No issue happened if there're more than 1 triple.

Maybe it's a corner case of applying MAX or MIN to one single triple under certain evaluationMode?

class Main {

	public static void main(final String[] args) {
		// see https://github.com/eclipse-rdf4j/rdf4j/tree/main/compliance/solr
		System.setProperty(
				"solr.solr.home", "<your-path-to-embedded-solr>");

		MemoryStore memoryStore = new MemoryStore();
		LuceneSail lucenesail = new LuceneSail();

		lucenesail.setParameter(LuceneSail.INDEX_CLASS_KEY, SolrIndex.class.getName());
		lucenesail.setParameter(SolrIndex.SERVER_KEY, "embedded:");

		lucenesail.setBaseSail(memoryStore);
		// have issue
		lucenesail.setEvaluationMode(TupleFunctionEvaluationMode.NATIVE);

		// have issue
		// lucenesail.setEvaluationMode(TupleFunctionEvaluationMode.SERVICE);

		// NO issue. Working Properly
		// lucenesail.setEvaluationMode(TupleFunctionEvaluationMode.TRIPLE_SOURCE);

		SailRepository repo = new SailRepository(lucenesail);

		repo.init();

		try (RepositoryConnection con = repo.getConnection()) {
			con.begin();
			final Resource subject = Values.iri(RDF.NAMESPACE, "subject1");
			final Literal object = Values.literal("object1");
			con.add(subject, RDFS.LABEL, object);

			// If there are 2 triples, no issue. Only happen when there is only one triple
//			final Resource subject2 = Values.iri(RDF.NAMESPACE, "subject2");
//			final Literal object2 = Values.literal("object2");
//			con.add(subject2, RDFS.LABEL, object2);

			con.commit();
		}

		List<BindingSet> results;

		try (RepositoryConnection con = repo.getConnection()) {
			TupleQuery tq = con.prepareTupleQuery(QueryLanguage.SPARQL, SEARCH_QUERY);
			results = QueryResults.asList(tq.evaluate());
		}
		System.out.println(results);
	}

	private static String SEARCH_QUERY =
			"""
					PREFIX search: <http://www.openrdf.org/contrib/lucenesail#>
					PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
					
					SELECT ?subj (MAX(?score) as ?score)
					  WHERE {
					  ?subj search:matches [
							  search:query "*object*";
							  search:property rdfs:label;
							  search:score ?score;
							  search:snippet ?snippet
						 ]
					}
					GROUP BY ?subj
					""";
}

891 [main] ERROR org.eclipse.rdf4j.query.algebra.evaluation.optimizer.ConstantOptimizer - Query evaluation exception caught
org.eclipse.rdf4j.query.QueryEvaluationException: Unsupported value expr type: class org.eclipse.rdf4j.query.algebra.Min
	at org.eclipse.rdf4j.query.algebra.evaluation.impl.DefaultEvaluationStrategy.precompile(DefaultEvaluationStrategy.java:907) ~[rdf4j-queryalgebra-evaluation-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.query.algebra.evaluation.optimizer.ConstantOptimizer$ConstantVisitor.meetUnaryValueOperator(ConstantOptimizer.java:228) ~[rdf4j-queryalgebra-evaluation-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.query.algebra.helpers.AbstractSimpleQueryModelVisitor.meet(AbstractSimpleQueryModelVisitor.java:369) ~[rdf4j-queryalgebra-model-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.query.algebra.Min.visit(Min.java:28) ~[rdf4j-queryalgebra-model-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.query.algebra.GroupElem.visitChildren(GroupElem.java:69) ~[rdf4j-queryalgebra-model-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.query.algebra.helpers.AbstractSimpleQueryModelVisitor.meet(AbstractSimpleQueryModelVisitor.java:269) ~[rdf4j-queryalgebra-model-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.query.algebra.GroupElem.visit(GroupElem.java:64) ~[rdf4j-queryalgebra-model-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.query.algebra.Group.visitChildren(Group.java:141) ~[rdf4j-queryalgebra-model-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.query.algebra.helpers.AbstractSimpleQueryModelVisitor.meetUnaryTupleOperator(AbstractSimpleQueryModelVisitor.java:595) ~[rdf4j-queryalgebra-model-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.query.algebra.helpers.AbstractSimpleQueryModelVisitor.meet(AbstractSimpleQueryModelVisitor.java:259) ~[rdf4j-queryalgebra-model-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.query.algebra.Group.visit(Group.java:133) ~[rdf4j-queryalgebra-model-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.query.algebra.UnaryTupleOperator.visitChildren(UnaryTupleOperator.java:72) ~[rdf4j-queryalgebra-model-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.query.algebra.Extension.visitChildren(Extension.java:99) ~[rdf4j-queryalgebra-model-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.query.algebra.helpers.AbstractSimpleQueryModelVisitor.meetUnaryTupleOperator(AbstractSimpleQueryModelVisitor.java:595) ~[rdf4j-queryalgebra-model-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.query.algebra.helpers.AbstractSimpleQueryModelVisitor.meet(AbstractSimpleQueryModelVisitor.java:234) ~[rdf4j-queryalgebra-model-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.query.algebra.Extension.visit(Extension.java:94) ~[rdf4j-queryalgebra-model-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.query.algebra.UnaryTupleOperator.visitChildren(UnaryTupleOperator.java:72) ~[rdf4j-queryalgebra-model-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.query.algebra.Projection.visitChildren(Projection.java:86) ~[rdf4j-queryalgebra-model-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.query.algebra.helpers.AbstractSimpleQueryModelVisitor.meetUnaryTupleOperator(AbstractSimpleQueryModelVisitor.java:595) ~[rdf4j-queryalgebra-model-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.query.algebra.helpers.AbstractSimpleQueryModelVisitor.meet(AbstractSimpleQueryModelVisitor.java:414) ~[rdf4j-queryalgebra-model-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.query.algebra.Projection.visit(Projection.java:80) ~[rdf4j-queryalgebra-model-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.query.algebra.UnaryTupleOperator.visitChildren(UnaryTupleOperator.java:72) ~[rdf4j-queryalgebra-model-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.query.algebra.helpers.AbstractSimpleQueryModelVisitor.meet(AbstractSimpleQueryModelVisitor.java:430) ~[rdf4j-queryalgebra-model-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.query.algebra.QueryRoot.visit(QueryRoot.java:41) ~[rdf4j-queryalgebra-model-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.query.algebra.evaluation.optimizer.ConstantOptimizer.optimize(ConstantOptimizer.java:77) ~[rdf4j-queryalgebra-evaluation-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.query.algebra.evaluation.impl.DefaultEvaluationStrategy.optimize(DefaultEvaluationStrategy.java:330) ~[rdf4j-queryalgebra-evaluation-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.sail.base.SailSourceConnection.evaluateInternal(SailSourceConnection.java:251) ~[rdf4j-sail-base-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.sail.helpers.AbstractSailConnection.evaluate(AbstractSailConnection.java:333) ~[rdf4j-sail-api-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.sail.helpers.SailConnectionWrapper.evaluate(SailConnectionWrapper.java:115) ~[rdf4j-sail-api-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.sail.lucene.LuceneSailConnection.evaluateInternal(LuceneSailConnection.java:473) ~[rdf4j-sail-lucene-api-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.sail.lucene.LuceneSailConnection.evaluate(LuceneSailConnection.java:406) ~[rdf4j-sail-lucene-api-5.0.3.jar:5.0.3]
	at org.eclipse.rdf4j.repository.sail.SailTupleQuery.evaluate(SailTupleQuery.java:52) ~[rdf4j-repository-sail-5.0.3.jar:5.0.3]
	at org.example.Main.main(Main.java:60) ~[classes/:?]

[odysa]

Under TRIPLE_SOURCE mode, LuceneSaiConnection uses the TupleFunctionEvaluationStrategy while others modes use the DefaultEvaluationStrategy

rdf4j/core/sail/lucene-api/src/main/java/org/eclipse/rdf4j/sail/lucene/LuceneSailConnection.java

Line 445 in b33d914

EvaluationStrategy strategy = new TupleFunctionEvaluationStrategy(

But TupleFunctionEvaluationStrategy has deprecated since 4.3.0.

/**
 * An {@link EvaluationStrategy} that has support for {@link TupleFunction}s.
 *
 * @deprecated since 4.3.0. Use {@link DefaultEvaluationStrategy} instead.
 */

[odysa]

Hello @hmottestad, I found the root cause.

In ConstantOptimizer, it precompiles and evaluates the constant value in the value expression.

rdf4j/core/queryalgebra/evaluation/src/main/java/org/eclipse/rdf4j/query/algebra/evaluation/optimizer/ConstantOptimizer.java

Lines 223 to 229 in b33d914

	protected void meetUnaryValueOperator(UnaryValueOperator unaryValueOp) {
	super.meetUnaryValueOperator(unaryValueOp);
	if (isConstant(unaryValueOp.getArg())) {
	try {
	Value value = strategy.precompile(unaryValueOp, context).evaluate(EmptyBindingSet.getInstance());
	unaryValueOp.replaceWith(new ValueConstant(value));

The example query meets the condition if isConstant because the MAX expr has a numerical literal value

rdf4j/core/queryalgebra/evaluation/src/main/java/org/eclipse/rdf4j/query/algebra/evaluation/optimizer/ConstantOptimizer.java

Lines 346 to 348 in b33d914

	private boolean isConstant(ValueExpr expr) {
	return expr instanceof ValueConstant || expr instanceof Var && ((Var) expr).hasValue();
	}

The precompile in DefaultEvaluationStrategy does not handle the cases of MAX(and other aggregate expr).
It will throw an exception of unspported expr type ...

rdf4j/core/queryalgebra/evaluation/src/main/java/org/eclipse/rdf4j/query/algebra/evaluation/impl/DefaultEvaluationStrategy.java

Lines 834 to 840 in b33d914

	public QueryValueEvaluationStep precompile(ValueExpr expr,
	QueryEvaluationContext context)
	throws QueryEvaluationException {
	if (expr instanceof Var) {
	return prepare((Var) expr, context);
	} else if (expr instanceof ValueConstant) {
	return prepare((ValueConstant) expr, context);

The literal value in MAX is from the BindingSetAssignmentVisitor, which replaces the ?score with the literal.

rdf4j/core/queryalgebra/evaluation/src/main/java/org/eclipse/rdf4j/query/algebra/evaluation/optimizer/BindingSetAssignmentInlinerOptimizer.java

Lines 57 to 63 in b33d914

	@Override
	public void meet(Var var) {
	if (bindingSet != null && bindingSet.hasBinding(var.getName())) {
	Value replacementValue = bindingSet.getValue(var.getName());
	var.replaceWith(new Var(var.getName(), replacementValue, var.isAnonymous(), var.isConstant()));
	}
	}

However, if there are more than 1 triple, the biningSet in BindingSetAssignmentVisitor will be null. It's because if the bsa.getBindingSets has the size > 1, the bindingSet will not be assigned.

rdf4j/core/queryalgebra/evaluation/src/main/java/org/eclipse/rdf4j/query/algebra/evaluation/optimizer/BindingSetAssignmentInlinerOptimizer.java

Lines 46 to 54 in b33d914

	public void meet(BindingSetAssignment bsa) {
	Iterator<BindingSet> iter = bsa.getBindingSets().iterator();
	if (iter.hasNext()) {
	BindingSet firstBindingSet = iter.next();
	if (!iter.hasNext()) {
	bindingSet = firstBindingSet;
	}
	}
	super.meet(bsa);

Therefore, it does not hit the if clause, and the value in MAX will be null. The precompile mentioned above will be skipped. As a result, no exception will be thrown if there are more than 1 triples.

rdf4j/core/queryalgebra/evaluation/src/main/java/org/eclipse/rdf4j/query/algebra/evaluation/optimizer/BindingSetAssignmentInlinerOptimizer.java

Line 59 in b33d914

if (bindingSet != null && bindingSet.hasBinding(var.getName())) {

[odysa]

BTW, to easily reproduce it, you may the below test case to

rdf4j/testsuites/lucene/src/main/java/org/eclipse/testsuite/rdf4j/sail/lucene/AbstractLuceneSailTest.java

Line 71 in b33d914

public abstract class AbstractLuceneSailTest {

@Test
public void testMaxFunction(){
	StringBuffer buffer = new StringBuffer();
	buffer.append("PREFIX search: <http://www.openrdf.org/contrib/lucenesail#>\n");
	buffer.append("SELECT ?subj (MAX(?score) as ?score)\n");
	buffer.append("WHERE {\n");
	buffer.append("  ?subj search:matches [\n");
	buffer.append("    search:query \"must_be_unique*\";\n");
	buffer.append("    search:property <urn:predicate1> ;\n");
	buffer.append("    search:score ?score;\n");
	buffer.append("    search:snippet ?snippet\n");
	buffer.append("  ]\n");
	buffer.append("}\n");
	buffer.append("GROUP BY ?subj\n");
	String q = buffer.toString();

	
	sail.setEvaluationMode(TupleFunctionEvaluationMode.NATIVE);
	configure(sail);

	List<BindingSet> results;
	try (RepositoryConnection connection = repository.getConnection()){
		connection.begin();
		connection.add(SUBJECT_3, PREDICATE_1, vf.createLiteral("must_be_unique"));
		connection.commit();
	}
	try (RepositoryConnection connection = repository.getConnection()) {
		TupleQuery query = connection.prepareTupleQuery(q);
		results = QueryResults.asList(query.evaluate());
	}
	assertEquals(1, results.size());
}

Expected to see the error in the std. QueryEvaluationException is caught and handled by logging. Is there any way to make this test case fail?

org.eclipse.rdf4j.query.QueryEvaluationException: Unsupported value expr type: class org.eclipse.rdf4j.query.algebra.Max

[odysa]

Maybe we can fix it by checking whether the parent node is a GroupElem because we cannot replace the child of GroupElem with a ValueConstant. The GroupElem requires children nodes to be AggregateOperator

boolean parentIsGroup = unaryValueOp.getParentNode() instanceof GroupElem;
if (!parentIsGroup && isConstant(unaryValueOp.getArg())) {
	try {
		Value value = strategy.precompile(unaryValueOp, context).evaluate(EmptyBindingSet.getInstance());
		unaryValueOp.replaceWith(new ValueConstant(value));

[JervenBolleman]

@odysa maybe we should implement a specific constant visitor method for the GroupElem types. Where we can implement a specific logic for constants.

[odysa]

@JervenBolleman
Can we add an extra field in the GroupElem to allow it hold a ValueConstant?

public class GroupElem extends AbstractQueryModelNode {
	private AggregateOperator operator;
	private ValueConstant valueConstant;

	@Override
	public <X extends Exception> void visitChildren(QueryModelVisitor<X> visitor) throws X {
		if(valueConstant != null) {
			valueConstant.visit(visitor);
			return;
		}
		operator.visit(visitor);
	}
	
	@Override
	public void replaceChildNode(QueryModelNode current, QueryModelNode replacement) {
	if (operator == current) {
		replacement.setParentNode(this);
		if (replacement instanceof ValueConstant) {
			valueConstant = (ValueConstant) replacement;
		} else if (replacement instanceof AggregateOperator) {
			operator = (AggregateOperator) replacement;
		}
	}
}

In the method of precompile in DefaultEvaluationStrategy

else if (expr instanceof AbstractAggregateOperator) {
	final Var var = (Var)((AbstractAggregateOperator) expr).getArg();
	return prepare(var, context);
} else if (expr == null) {
	throw new IllegalArgumentException("expr must not be null");
} 

[JervenBolleman]

@odysa I was wondering if instead we should make a new ConstantAggregateOperator instead? Then we might be able to skip a lot of work in the GroupIterator.

Test case to add into the ConstantOptimizerTest

	@Test
	public void testAggregateOptimization() throws RDF4JException {
		String query = "prefix ex: <ex:>" + "select (max(1) AS ?a) \n " + "where {\n" + "?x a ?z \n"
				+ "}";

		ParsedQuery pq = QueryParserUtil.parseQuery(QueryLanguage.SPARQL, query, null);
		EvaluationStrategy strategy = new DefaultEvaluationStrategy(new EmptyTripleSource(), null);
		TupleExpr original = pq.getTupleExpr();

		final AlgebraFinder finder = new AlgebraFinder();
		original.visit(finder);
		assertTrue(finder.groupElemFound);

		// reset for re-use on optimized query
		finder.reset();

		QueryBindingSet constants = new QueryBindingSet();
		constants.addBinding("x", SimpleValueFactory.getInstance().createLiteral("foo"));
		constants.addBinding("z", SimpleValueFactory.getInstance().createLiteral("bar"));

		TupleExpr optimized = optimize(pq.getTupleExpr().clone(), constants, strategy);

		optimized.visit(finder);
		assertThat(finder.functionCallFound).isFalse();

		CloseableIteration<BindingSet> result = strategy.precompile(optimized)
				.evaluate(
						new EmptyBindingSet());
		assertNotNull(result);
		assertTrue(result.hasNext());
		BindingSet bindings = result.next();
		assertTrue(bindings.hasBinding("a"));
		assertEquals(1, ((Literal) bindings.getBinding("a").getValue()).intValue());
	}

Then add

	@Override
		public void meet(Avg node) throws RuntimeException {
			optimizeUnaryValueExpr(node);
		}

		@Override
		public void meet(Max node) throws RuntimeException {
			optimizeUnaryValueExpr(node);
		}

		private void optimizeUnaryValueExpr(UnaryValueOperator node) {
			if (isConstant(node.getArg())) {
				QueryModelNode parent = node.getParentNode();
				if (parent instanceof GroupElem) {
					GroupElem ge = (GroupElem) parent;
					ge.setOperator(new ConstantAggregateOperator(node.getArg()));
				} else if (parent instanceof ExtensionElem) {
					ExtensionElem ee = (ExtensionElem) parent;
					ee.replaceChildNode(node, node.getArg());
				}
			}
		}

		@Override
		public void meet(Min node) throws RuntimeException {
			optimizeUnaryValueExpr(node);
		}

		@Override
		public void meet(Sample node) throws RuntimeException {
			optimizeUnaryValueExpr(node);
		}

		@Override
		public void meet(Sum node) throws RuntimeException {
			optimizeUnaryValueExpr(node);
		}

to the ConstantVisitor.

Which is enough to pass that specific test, but unlikely to fix all issues.