Lazy load relations and cached query optimization

Signed-off-by: ntisseyre <ntisseyre@apple.com>

docs/basics/transactions.md

@@ -326,6 +326,9 @@ following aspects of a transaction to be configured:
     cache access during read operations. Doesn't have any effect if database 
     level cache was disabled via config `cache.db-cache`.
 
+-   `lazyLoadRelations()` - Set lazy-load for all properties and edges of the vertex: ids and values are deserialized upon demand.
+    When enabled, it can have a boost on large-scale read operations, if only certain types of relations are being read from the vertex.
+
 Once, the desired configuration options have been specified, the new
 transaction is started via `start()` which returns a
 `JanusGraphTransaction`.

janusgraph-backend-testutils/src/main/java/org/janusgraph/graphdb/JanusGraphTest.java

@@ -116,6 +116,7 @@
 import org.janusgraph.graphdb.database.util.StaleIndexRecordUtil;
 import org.janusgraph.graphdb.internal.ElementCategory;
 import org.janusgraph.graphdb.internal.ElementLifeCycle;
+import org.janusgraph.graphdb.internal.InternalElement;
 import org.janusgraph.graphdb.internal.InternalRelationType;
 import org.janusgraph.graphdb.internal.InternalVertex;
 import org.janusgraph.graphdb.internal.Order;
@@ -129,7 +130,6 @@
 import org.janusgraph.graphdb.query.condition.PredicateCondition;
 import org.janusgraph.graphdb.query.index.IndexSelectionUtil;
 import org.janusgraph.graphdb.query.profile.QueryProfiler;
-import org.janusgraph.graphdb.relations.AbstractEdge;
 import org.janusgraph.graphdb.relations.RelationIdentifier;
 import org.janusgraph.graphdb.relations.StandardEdge;
 import org.janusgraph.graphdb.relations.StandardVertexProperty;
@@ -425,7 +425,7 @@ public void testUpdatePropertyPropThenRemoveVertex() {
     public void testUpdateEdgePropertyThenRemoveEdge() {
         initializeGraphWithVerticesAndEdges();
         // normal edge
-        AbstractEdge edge = (AbstractEdge) graph.traversal().E().has("_e", 1).next();
+        InternalElement edge = (InternalElement) graph.traversal().E().has("_e", 1).next();
         assertTrue(ElementLifeCycle.isLoaded(edge.getLifeCycle()));
         Object id = edge.id();
 
@@ -452,7 +452,7 @@ public void testUpdateEdgePropertyThenRemoveEdge() {
     public void testUpdateForkEdgePropertyThenRemoveEdge() {
         initializeGraphWithVerticesAndEdges();
         // fork edge
-        AbstractEdge edge = (AbstractEdge) graph.traversal().E().has("_e", 2).next();
+        InternalElement edge = (InternalElement) graph.traversal().E().has("_e", 2).next();
         assertTrue(ElementLifeCycle.isLoaded(edge.getLifeCycle()));
         Object id = edge.id();
 
@@ -483,7 +483,7 @@ public void testUpdateForkEdgePropertyThenRemoveEdge() {
     @Test
     public void testUpdateForkEdgePropertyThenFindEdgeById() {
         initializeGraphWithVerticesAndEdges();
-        AbstractEdge edge = (AbstractEdge) graph.traversal().E().has("_e", 2).next();
+        InternalElement edge = (InternalElement) graph.traversal().E().has("_e", 2).next();
         Object id = edge.id();
 
         edge.property("_e", -2);

janusgraph-backend-testutils/src/main/java/org/janusgraph/graphdb/database/LazyLoadGraphTest.java

@@ -0,0 +1,66 @@
+// Copyright 2024 JanusGraph Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package org.janusgraph.graphdb.database;
+
+import org.apache.tinkerpop.gremlin.process.traversal.TraversalStrategies;
+import org.apache.tinkerpop.gremlin.structure.Graph;
+import org.janusgraph.graphdb.configuration.GraphDatabaseConfiguration;
+import org.janusgraph.graphdb.tinkerpop.optimize.strategy.AdjacentVertexFilterOptimizerStrategy;
+import org.janusgraph.graphdb.tinkerpop.optimize.strategy.AdjacentVertexHasIdOptimizerStrategy;
+import org.janusgraph.graphdb.tinkerpop.optimize.strategy.AdjacentVertexHasUniquePropertyOptimizerStrategy;
+import org.janusgraph.graphdb.tinkerpop.optimize.strategy.AdjacentVertexIsOptimizerStrategy;
+import org.janusgraph.graphdb.tinkerpop.optimize.strategy.JanusGraphHasStepStrategy;
+import org.janusgraph.graphdb.tinkerpop.optimize.strategy.JanusGraphIoRegistrationStrategy;
+import org.janusgraph.graphdb.tinkerpop.optimize.strategy.JanusGraphLocalQueryOptimizerStrategy;
+import org.janusgraph.graphdb.tinkerpop.optimize.strategy.JanusGraphMixedIndexAggStrategy;
+import org.janusgraph.graphdb.tinkerpop.optimize.strategy.JanusGraphMixedIndexCountStrategy;
+import org.janusgraph.graphdb.tinkerpop.optimize.strategy.JanusGraphMultiQueryStrategy;
+import org.janusgraph.graphdb.tinkerpop.optimize.strategy.JanusGraphStepStrategy;
+import org.janusgraph.graphdb.tinkerpop.optimize.strategy.JanusGraphUnusedMultiQueryRemovalStrategy;
+import org.janusgraph.graphdb.transaction.StandardTransactionBuilder;
+
+public class LazyLoadGraphTest extends StandardJanusGraph {
+
+    static {
+        TraversalStrategies graphStrategies =
+            TraversalStrategies.GlobalCache.getStrategies(Graph.class)
+                .clone()
+                .addStrategies(AdjacentVertexFilterOptimizerStrategy.instance(),
+                    AdjacentVertexHasIdOptimizerStrategy.instance(),
+                    AdjacentVertexIsOptimizerStrategy.instance(),
+                    AdjacentVertexHasUniquePropertyOptimizerStrategy.instance(),
+                    JanusGraphLocalQueryOptimizerStrategy.instance(),
+                    JanusGraphHasStepStrategy.instance(),
+                    JanusGraphMultiQueryStrategy.instance(),
+                    JanusGraphUnusedMultiQueryRemovalStrategy.instance(),
+                    JanusGraphMixedIndexAggStrategy.instance(),
+                    JanusGraphMixedIndexCountStrategy.instance(),
+                    JanusGraphStepStrategy.instance(),
+                    JanusGraphIoRegistrationStrategy.instance());
+
+        //Register with cache
+        TraversalStrategies.GlobalCache.registerStrategies(LazyLoadGraphTest.class, graphStrategies);
+    }
+
+    public LazyLoadGraphTest(GraphDatabaseConfiguration configuration) {
+        super(configuration);
+    }
+
+    @Override
+    public StandardTransactionBuilder buildTransaction() {
+        return (StandardTransactionBuilder) new StandardTransactionBuilder(getConfiguration(), this)
+            .lazyLoadRelations();
+    }
+}

janusgraph-core/src/main/java/org/janusgraph/core/JanusGraphLazyEdge.java

@@ -0,0 +1,55 @@
+// Copyright 2024 JanusGraph Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package org.janusgraph.core;
+
+import org.apache.tinkerpop.gremlin.structure.Direction;
+import org.apache.tinkerpop.gremlin.structure.Vertex;
+import org.janusgraph.diskstorage.Entry;
+import org.janusgraph.graphdb.internal.InternalRelation;
+import org.janusgraph.graphdb.internal.InternalRelationType;
+import org.janusgraph.graphdb.internal.InternalVertex;
+import org.janusgraph.graphdb.transaction.StandardJanusGraphTx;
+
+public class JanusGraphLazyEdge extends JanusGraphLazyRelation implements JanusGraphEdge {
+
+    public JanusGraphLazyEdge(InternalRelation janusGraphRelation,
+                                  final InternalVertex vertex,
+                                  final StandardJanusGraphTx tx,
+                                  final InternalRelationType type) {
+        super(janusGraphRelation, vertex, tx, type);
+    }
+
+    public JanusGraphLazyEdge(Entry dataEntry,
+                                  final InternalVertex vertex,
+                                  final StandardJanusGraphTx tx,
+                                  final InternalRelationType type) {
+        super(dataEntry, vertex, tx, type);
+    }
+
+    private JanusGraphEdge loadEdge() {
+        assert this.isEdge();
+        return (JanusGraphEdge) this.loadValue();
+    }
+
+    @Override
+    public JanusGraphVertex vertex(Direction dir) {
+        return this.loadEdge().vertex(dir);
+    }
+
+    @Override
+    public JanusGraphVertex otherVertex(Vertex vertex) {
+        return this.loadEdge().otherVertex(vertex);
+    }
+}