Fix edge direction problem for Neo4j storage

lightrag/kg/neo4j_impl.py

@@ -665,31 +665,56 @@ class Neo4JStorage(BaseGraphStorage):
     ) -> dict[str, list[tuple[str, str]]]:
         """
         Batch retrieve edges for multiple nodes in one query using UNWIND.
+        For each node, returns both outgoing and incoming edges to properly represent
+        the undirected graph nature.
 
         Args:
             node_ids: List of node IDs (entity_id) for which to retrieve edges.
 
         Returns:
             A dictionary mapping each node ID to its list of edge tuples (source, target).
+            For each node, the list includes both:
+            - Outgoing edges: (queried_node, connected_node)
+            - Incoming edges: (connected_node, queried_node)
         """
         async with self._driver.session(
             database=self._DATABASE, default_access_mode="READ"
         ) as session:
+            # Query to get both outgoing and incoming edges
             query = """
                 UNWIND $node_ids AS id
                 MATCH (n:base {entity_id: id})
                 OPTIONAL MATCH (n)-[r]-(connected:base)
-                RETURN id AS queried_id, n.entity_id AS source_entity_id, connected.entity_id AS target_entity_id
+                RETURN id AS queried_id, n.entity_id AS node_entity_id,
+                       connected.entity_id AS connected_entity_id,
+                       startNode(r).entity_id AS start_entity_id
             """
             result = await session.run(query, node_ids=node_ids)
+
             # Initialize the dictionary with empty lists for each node ID
             edges_dict = {node_id: [] for node_id in node_ids}
+
+            # Process results to include both outgoing and incoming edges
             async for record in result:
                 queried_id = record["queried_id"]
-                source_label = record["source_entity_id"]
-                target_label = record["target_entity_id"]
-                if source_label and target_label:
-                    edges_dict[queried_id].append((source_label, target_label))
+                node_entity_id = record["node_entity_id"]
+                connected_entity_id = record["connected_entity_id"]
+                start_entity_id = record["start_entity_id"]
+
+                # Skip if either node is None
+                if not node_entity_id or not connected_entity_id:
+                    continue
+
+                # Determine the actual direction of the edge
+                # If the start node is the queried node, it's an outgoing edge
+                # Otherwise, it's an incoming edge
+                if start_entity_id == node_entity_id:
+                    # Outgoing edge: (queried_node -> connected_node)
+                    edges_dict[queried_id].append((node_entity_id, connected_entity_id))
+                else:
+                    # Incoming edge: (connected_node -> queried_node)
+                    edges_dict[queried_id].append((connected_entity_id, node_entity_id))
+
             await result.consume()  # Ensure results are fully consumed
             return edges_dict