Don't attempt to decode NULL graph entities (#69)

* Don't attempt to decode NULL graph entities

* Remove unnecessary logic from parse_path

* Add test for null graph entities

Author: jeffreylovitz

redisgraph/query_result.py

@@ -104,6 +104,10 @@ def parse_entity_properties(self, props):
         return properties
 
     def parse_node(self, cell):
+        # Return None if we received a null value.
+        if self.is_null_scalar(cell):
+            return None
+
         # Node ID (integer),
         # [label string offset (integer)],
         # [[name, value type, value] X N]
@@ -116,6 +120,10 @@ def parse_node(self, cell):
         return Node(node_id=node_id, label=label, properties=properties)
 
     def parse_edge(self, cell):
+        # Return None if we received a null value.
+        if self.is_null_scalar(cell):
+            return None
+
         # Edge ID (integer),
         # reltype string offset (integer),
         # src node ID offset (integer),
@@ -219,6 +227,9 @@ def pretty_print(self):
     def is_empty(self):
         return len(self.result_set) == 0
 
+    def is_null_scalar(self, cell):
+        return cell == [ResultSetScalarTypes.VALUE_NULL, None]
+
     @staticmethod
     def _get_value(prop, statistics):
         for stat in statistics:

test.py

@@ -162,6 +162,30 @@ def test_stringify_query_result(self):
 
         redis_graph.delete()
 
+    def test_optional_match(self):
+        redis_graph = Graph('optional', self.r)
+
+        # Build a graph of form (a)-[R]->(b)
+        node0 = Node(node_id=0, label="L1", properties={'value': 'a'})
+        node1 = Node(node_id=1, label="L1", properties={'value': 'b'})
+
+        edge01 = Edge(node0, "R", node1, edge_id=0)
+
+        redis_graph.add_node(node0)
+        redis_graph.add_node(node1)
+        redis_graph.add_edge(edge01)
+
+        redis_graph.flush()
+
+        # Issue a query that collects all outgoing edges from both nodes (the second has none).
+        query = """MATCH (a) OPTIONAL MATCH (a)-[e]->(b) RETURN a, e, b ORDER BY a.value"""
+        expected_results = [[node0, edge01, node1],
+                            [node1, None, None]]
+
+        result = redis_graph.query(query)
+        self.assertEqual(expected_results, result.result_set)
+
+        redis_graph.delete()
 
 if __name__ == '__main__':
     unittest.main()