Fix: Speedup listing of metadata

src/SQL2Linked/Implementations/ResourceStructuralData.cs

@@ -20,6 +20,8 @@ namespace SQL2Linked.Implementations
         private ProjectResourceModel ProjectResourceModel = new ProjectResourceModel();
         private LicenseModel LicenseModel = new LicenseModel();
 
+        private readonly Dictionary<string, string> _targetClassMap = new Dictionary<string, string>();
+
         // Override to also receive deleted resources
         public override IEnumerable<Resource> GetAll()
         {
@@ -134,11 +136,13 @@ namespace SQL2Linked.Implementations
                 AssertToGraphLiteralNode(graph, resourceGraphName, cosc + "terms/resource#deleted", entry.Deleted.ToString().ToLower(), new Uri("http://www.w3.org/2001/XMLSchema#boolean"));
                 Console.WriteLine($"For project '{entry.DisplayName}' will migrate triple '{resourceGraphName} {cosc}terms/resource#deleted {entry.Deleted}'. ");
 
+                var targetClass = GetTargetClass(entry);
+
                 SparqlParameterizedString cmdString = new SparqlParameterizedString
                 {
                     CommandText = "SELECT DISTINCT ?g " +
                                     "WHERE {" +
-                                        "GRAPH ?g { ?s ?p ?o } . " +
+                                        "GRAPH ?g { ?s a <" + targetClass + "> } . " +
                                         "FILTER(contains(STR(?g), \"" + resourceHandleName + "@\"))" +
                                      "}"
                 };
@@ -188,5 +192,36 @@ namespace SQL2Linked.Implementations
 
             return graphs;
         }
+
+        /// <summary>
+        /// Since Application Profile URL does not have to be the targetClass, resolve it first
+        /// </summary>
+        /// <param name="entry"></param>
+        /// <returns></returns>
+        private string GetTargetClass(Resource entry)
+        {
+            if (_targetClassMap.ContainsKey(entry.ApplicationProfile))
+            {
+                return _targetClassMap[entry.ApplicationProfile];
+            }
+
+            var targetClassCmdString = new SparqlParameterizedString
+            {
+                CommandText = "SELECT DISTINCT ?targetClass " +
+                                "WHERE { @applicationProfile <http://www.w3.org/ns/shacl#targetClass> ?targetClass }"
+            };
+            targetClassCmdString.SetUri("applicationProfile", new Uri(entry.ApplicationProfile));
+            var targetClassResultSet = QueryEndpoint.QueryWithResultSet(targetClassCmdString.ToString());
+
+            var targetClass = entry.ApplicationProfile;
+            foreach (var result in targetClassResultSet)
+            {
+                targetClass = result[0].ToString();
+            }
+
+            _targetClassMap.Add(entry.ApplicationProfile, targetClass);
+
+            return targetClass;
+        }
     }
 }