Return proper DeletionResult when deleting non-exisitng relationship types

Co-authored-by: Florentin Dörre <florentin.dorre@neotechnology.com>

Author: Mats-SX

core/src/main/java/org/neo4j/gds/core/loading/CSRGraphStore.java

@@ -448,9 +448,7 @@ public DeletionResult deleteRelationships(RelationshipType relationshipType) {
         return DeletionResult.of(builder ->
             updateGraphStore(graphStore -> {
                 var removedTopology = graphStore.relationships.remove(relationshipType);
-                if (removedTopology != null) {
-                    builder.deletedRelationships(removedTopology.elementCount());
-                }
+                builder.deletedRelationships(removedTopology == null ? 0 : removedTopology.elementCount());
 
                 var removedProperties = graphStore.relationshipProperties.remove(relationshipType);
 

core/src/test/java/org/neo4j/gds/core/loading/CSRGraphStoreTest.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) "Neo4j"
+ * Neo4j Sweden AB [http://neo4j.com]
+ *
+ * This file is part of Neo4j.
+ *
+ * Neo4j is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.neo4j.gds.core.loading;
+
+import org.junit.jupiter.api.Test;
+import org.neo4j.gds.RelationshipType;
+import org.neo4j.gds.gdl.GdlFactory;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class CSRGraphStoreTest {
+
+    @Test
+    void deleteAdditionalRelationshipTypes() {
+        GdlFactory factory = GdlFactory.of("(b)-[:REL {x: 1}]->(a), (b)-[:REL]->(c)");
+        var graphStore = factory.build();
+
+        var del1 = graphStore.deleteRelationships(RelationshipType.of("REL"));
+
+        assertThat(del1.deletedRelationships()).isEqualTo(2);
+        assertThat(del1.deletedProperties()).containsEntry("x", 2L).hasSize(1);
+
+        var del2 = graphStore.deleteRelationships(RelationshipType.of("REL"));
+
+        assertThat(del2.deletedRelationships()).isEqualTo(0);
+        assertThat(del2.deletedProperties()).isEmpty();
+    }
+
+}