TINKERPOP-919 Added supportsDuplicateMultiProperties()

CHANGELOG.asciidoc

@@ -26,6 +26,7 @@ image::https://raw.githubusercontent.com/apache/tinkerpop/master/docs/static/ima
 TinkerPop 3.2.4 (Release Date: NOT OFFICIALLY RELEASED YET)
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
+* Added `VertexFeatures.supportsDuplicateMultiProperties()` for graphs that only support unique values in multi-properties.
 * Deprecated the "performance" tests in `OptIn`.
 * Fixed a severe bug where `GraphComputer` strategies are not being loaded until the second use of the traversal source.
 

docs/src/upgrade/release-3.2.x-incubating.asciidoc

@@ -35,6 +35,14 @@ Upgrading for Providers
 Graph Database Providers
 ^^^^^^^^^^^^^^^^^^^^^^^^
 
+Duplicate Multi-Properties
+++++++++++++++++++++++++++
+
+Added `supportsDuplicateMultiProperties` to `VertexFeatures` so that graph provider who only support unique values as
+multi-properties have more flexibility in describing their graph capabilities.
+
+See: https://issues.apache.org/jira/browse/TINKERPOP-919[TINKERPOP-919]
+
 Deprecated Performance OptIn
 ++++++++++++++++++++++++++++
 

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/structure/Graph.java

@@ -24,6 +24,7 @@
 import org.apache.tinkerpop.gremlin.process.traversal.TraversalEngine;
 import org.apache.tinkerpop.gremlin.process.traversal.TraversalSource;
 import org.apache.tinkerpop.gremlin.process.traversal.dsl.graph.GraphTraversalSource;
+import org.apache.tinkerpop.gremlin.process.traversal.engine.ComputerTraversalEngine;
 import org.apache.tinkerpop.gremlin.structure.io.Io;
 import org.apache.tinkerpop.gremlin.structure.io.IoRegistry;
 import org.apache.tinkerpop.gremlin.structure.util.FeatureDescriptor;
@@ -512,6 +513,7 @@ public default VariableFeatures variables() {
         public interface VertexFeatures extends ElementFeatures {
             public static final String FEATURE_ADD_VERTICES = "AddVertices";
             public static final String FEATURE_MULTI_PROPERTIES = "MultiProperties";
+            public static final String FEATURE_DUPLICATE_MULTI_PROPERTIES = "DuplicateMultiProperties";
             public static final String FEATURE_META_PROPERTIES = "MetaProperties";
             public static final String FEATURE_REMOVE_VERTICES = "RemoveVertices";
 
@@ -549,6 +551,16 @@ public default boolean supportsMultiProperties() {
                 return true;
             }
 
+            /**
+             * Determines if a {@link Vertex} can support non-unique values on the same key. For this value to be
+             * {@code true}, then {@link #supportsMetaProperties()} must also return true. By default this method,
+             * just returns what {@link #supportsMultiProperties()} returns.
+             */
+            @FeatureDescriptor(name = FEATURE_DUPLICATE_MULTI_PROPERTIES)
+            public default boolean supportsDuplicateMultiProperties() {
+                return supportsMultiProperties();
+            }
+
             /**
              * Determines if a {@link Vertex} can support properties on vertex properties.  It is assumed that a
              * graph will support all the same data types for meta-properties that are supported for regular

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/structure/VertexProperty.java

@@ -99,6 +99,10 @@ public static UnsupportedOperationException multiPropertiesNotSupported() {
             return new UnsupportedOperationException("Multiple properties on a vertex is not supported");
         }
 
+        public static UnsupportedOperationException identicalMultiPropertiesNotSupported() {
+            return new UnsupportedOperationException("Multiple properties on a vertex is supported, but a single key may not hold the same value more than once");
+        }
+
         public static UnsupportedOperationException metaPropertiesNotSupported() {
             return new UnsupportedOperationException("Properties on a vertex property is not supported");
         }

gremlin-test/src/main/java/org/apache/tinkerpop/gremlin/structure/FeatureSupportTest.java

@@ -697,7 +697,8 @@ public void shouldEnableFeatureOnGraphIfNotEnabled() throws Exception {
             "multiPropertiesNotSupported",
             "metaPropertiesNotSupported",
             "userSuppliedIdsNotSupported",
-            "userSuppliedIdsOfThisTypeNotSupported"
+            "userSuppliedIdsOfThisTypeNotSupported",
+            "identicalMultiPropertiesNotSupported"
     })
     @ExceptionCoverage(exceptionClass = Element.Exceptions.class, methods = {
             "propertyRemovalNotSupported"
@@ -873,6 +874,22 @@ public void shouldSupportRemovePropertyIfAPropertyCanBeRemoved() throws Exceptio
             }
         }
 
+        @Test
+        @FeatureRequirement(featureClass = Graph.Features.EdgeFeatures.class, feature = Graph.Features.EdgeFeatures.FEATURE_ADD_EDGES)
+        @FeatureRequirement(featureClass = Graph.Features.VertexFeatures.class, feature = Graph.Features.VertexFeatures.FEATURE_ADD_VERTICES)
+        @FeatureRequirement(featureClass = Graph.Features.VertexFeatures.class, feature = Graph.Features.VertexFeatures.FEATURE_ADD_PROPERTY)
+        @FeatureRequirement(featureClass = Graph.Features.VertexFeatures.class, feature = VertexFeatures.FEATURE_MULTI_PROPERTIES)
+        @FeatureRequirement(featureClass = Graph.Features.VertexFeatures.class, feature = VertexFeatures.FEATURE_DUPLICATE_MULTI_PROPERTIES, supported = false)
+        public void shouldSupportIdenticalMultiPropertyIfTheSameKeyCanBeAssignedSameValueMoreThanOnce() throws Exception {
+            try {
+                final Vertex v = graph.addVertex("name", "stephen", "name", "stephen");
+                if (2 == IteratorUtils.count(v.properties()))
+                    fail(String.format(INVALID_FEATURE_SPECIFICATION, VertexFeatures.class.getSimpleName(), VertexFeatures.FEATURE_DUPLICATE_MULTI_PROPERTIES));
+            } catch (Exception ex) {
+                validateException(VertexProperty.Exceptions.identicalMultiPropertiesNotSupported(), ex);
+            }
+        }
+
         @Test
         @FeatureRequirement(featureClass = Graph.Features.EdgeFeatures.class, feature = Graph.Features.EdgeFeatures.FEATURE_ADD_EDGES)
         @FeatureRequirement(featureClass = Graph.Features.VertexFeatures.class, feature = Graph.Features.VertexFeatures.FEATURE_ADD_VERTICES)
@@ -1023,7 +1040,13 @@ public void shouldSupportADataTypeIfVertexHasPropertyEnabled() {
         @Test
         public void shouldSupportRegularTransactionsIfThreadedTransactionsAreEnabled() {
             if (graphFeatures.supportsThreadedTransactions())
-                assertTrue(graphFeatures.supportsThreadedTransactions());
+                assertThat(graphFeatures.supportsThreadedTransactions(), is(true));
+        }
+
+        @Test
+        public void shouldSupportMultiPropertiesIfSupportingIdenticalMultiProperties() {
+            if (vertexFeatures.supportsDuplicateMultiProperties())
+                assertThat(vertexFeatures.supportsMultiProperties(), is(true));
         }
     }
 }

gremlin-test/src/main/java/org/apache/tinkerpop/gremlin/structure/VertexPropertyTest.java

@@ -34,6 +34,7 @@
 import java.util.UUID;
 
 import static org.hamcrest.Matchers.hasItem;
+import static org.hamcrest.collection.IsIterableContainingInOrder.contains;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotEquals;
 import static org.junit.Assert.assertThat;
@@ -288,11 +289,8 @@ public void shouldHandleSetVertexProperties() {
                     }
                 }
             });
-
-
         }
 
-
         @Test
         @FeatureRequirement(featureClass = Graph.Features.VertexFeatures.class, feature = Graph.Features.VertexFeatures.FEATURE_META_PROPERTIES)
         @FeatureRequirement(featureClass = Graph.Features.VertexFeatures.class, feature = Graph.Features.VertexFeatures.FEATURE_MULTI_PROPERTIES)
@@ -329,6 +327,28 @@ public void shouldRespectWhatAreEdgesAndWhatArePropertiesInMultiProperties() {
             assertEquals(0, IteratorUtils.count(newMexico.properties(T.key.getAccessor())));
             assertEquals(0, IteratorUtils.count(newMexico.properties(T.value.getAccessor())));
         }
+
+        @Test
+        @FeatureRequirementSet(FeatureRequirementSet.Package.VERTICES_ONLY)
+        @FeatureRequirement(featureClass = Graph.Features.VertexFeatures.class, feature = Graph.Features.VertexFeatures.FEATURE_MULTI_PROPERTIES)
+        @FeatureRequirement(featureClass = Graph.Features.VertexFeatures.class, feature = Graph.Features.VertexFeatures.FEATURE_DUPLICATE_MULTI_PROPERTIES)
+        public void shouldAllowIdenticalValuedMultiProperties() {
+            final Vertex v = graph.addVertex();
+            v.property(VertexProperty.Cardinality.list, "name", "stephen");
+            v.property(VertexProperty.Cardinality.list, "name", "stephen");
+            v.property(VertexProperty.Cardinality.list, "name", "steve");
+            v.property(VertexProperty.Cardinality.list, "name", "stephen");
+            v.property(VertexProperty.Cardinality.list, "color", "red");
+
+            tryCommit(graph, g -> {
+                final Vertex vertex = graph.vertices(v).next();
+                assertEquals(4, IteratorUtils.count(vertex.properties("name")));
+                assertEquals(1, IteratorUtils.count(vertex.properties("color")));
+                assertEquals(5, IteratorUtils.count(vertex.properties()));
+
+                assertThat(IteratorUtils.set(vertex.values("name")), contains("stephen", "steve"));
+            });
+        }
     }
 
     public static class VertexPropertyRemoval extends AbstractGremlinTest {