Enhance Neo4j graph storage with error handling and label validation

- Add label existence check and validation methods in Neo4j implementation
- Improve error handling in get_node, get_edge, and upsert methods
- Add default values and logging for missing edge properties
- Ensure consistent label processing across graph storage methods

lightrag/kg/neo4j_impl.py

@@ -143,9 +143,27 @@ class Neo4JStorage(BaseGraphStorage):
     async def index_done_callback(self):
         print("KG successfully indexed.")
 
-    async def has_node(self, node_id: str) -> bool:
+    async def _label_exists(self, label: str) -> bool:
-        entity_name_label = node_id.strip('"')
+        """Check if a label exists in the Neo4j database."""
+        query = "CALL db.labels() YIELD label RETURN label"
+        try:
+            async with self._driver.session(database=self._DATABASE) as session:
+                result = await session.run(query)
+                labels = [record["label"] for record in await result.data()]
+                return label in labels
+        except Exception as e:
+            logger.error(f"Error checking label existence: {e}")
+            return False
 
+    async def _ensure_label(self, label: str) -> str:
+        """Ensure a label exists by validating it."""
+        clean_label = label.strip('"')
+        if not await self._label_exists(clean_label):
+            logger.warning(f"Label '{clean_label}' does not exist in Neo4j")
+        return clean_label
+
+    async def has_node(self, node_id: str) -> bool:
+        entity_name_label = await self._ensure_label(node_id)
         async with self._driver.session(database=self._DATABASE) as session:
             query = (
                 f"MATCH (n:`{entity_name_label}`) RETURN count(n) > 0 AS node_exists"
@@ -174,8 +192,17 @@ class Neo4JStorage(BaseGraphStorage):
             return single_result["edgeExists"]
 
     async def get_node(self, node_id: str) -> Union[dict, None]:
+        """Get node by its label identifier.
+
+        Args:
+            node_id: The node label to look up
+
+        Returns:
+            dict: Node properties if found
+            None: If node not found
+        """
         async with self._driver.session(database=self._DATABASE) as session:
-            entity_name_label = node_id.strip('"')
+            entity_name_label = await self._ensure_label(node_id)
             query = f"MATCH (n:`{entity_name_label}`) RETURN n"
             result = await session.run(query)
             record = await result.single()
@@ -226,38 +253,73 @@ class Neo4JStorage(BaseGraphStorage):
     async def get_edge(
         self, source_node_id: str, target_node_id: str
     ) -> Union[dict, None]:
-        entity_name_label_source = source_node_id.strip('"')
+        """Find edge between two nodes identified by their labels.
-        entity_name_label_target = target_node_id.strip('"')
-        """
-        Find all edges between nodes of two given labels
 
         Args:
-            source_node_label (str): Label of the source nodes
+            source_node_id (str): Label of the source node
-            target_node_label (str): Label of the target nodes
+            target_node_id (str): Label of the target node
 
         Returns:
-            list: List of all relationships/edges found
+            dict: Edge properties if found, with at least {"weight": 0.0}
+            None: If error occurs
         """
-        async with self._driver.session(database=self._DATABASE) as session:
+        try:
-            query = f"""
+            entity_name_label_source = source_node_id.strip('"')
-            MATCH (start:`{entity_name_label_source}`)-[r]->(end:`{entity_name_label_target}`)
+            entity_name_label_target = target_node_id.strip('"')
-            RETURN properties(r) as edge_properties
-            LIMIT 1
-            """.format(
-                entity_name_label_source=entity_name_label_source,
-                entity_name_label_target=entity_name_label_target,
-            )
 
-            result = await session.run(query)
+            async with self._driver.session(database=self._DATABASE) as session:
-            record = await result.single()
+                query = f"""
-            if record:
+                MATCH (start:`{entity_name_label_source}`)-[r]->(end:`{entity_name_label_target}`)
-                result = dict(record["edge_properties"])
+                RETURN properties(r) as edge_properties
-                logger.debug(
+                LIMIT 1
-                    f"{inspect.currentframe().f_code.co_name}:query:{query}:result:{result}"
+                """.format(
+                    entity_name_label_source=entity_name_label_source,
+                    entity_name_label_target=entity_name_label_target,
                 )
-                return result
+
-            else:
+                result = await session.run(query)
-                return None
+                record = await result.single()
+                if record and "edge_properties" in record:
+                    try:
+                        result = dict(record["edge_properties"])
+                        # Ensure required keys exist with defaults
+                        required_keys = {
+                            "weight": 0.0,
+                            "source_id": None,
+                            "target_id": None,
+                        }
+                        for key, default_value in required_keys.items():
+                            if key not in result:
+                                result[key] = default_value
+                                logger.warning(
+                                    f"Edge between {entity_name_label_source} and {entity_name_label_target} "
+                                    f"missing {key}, using default: {default_value}"
+                                )
+
+                        logger.debug(
+                            f"{inspect.currentframe().f_code.co_name}:query:{query}:result:{result}"
+                        )
+                        return result
+                    except (KeyError, TypeError, ValueError) as e:
+                        logger.error(
+                            f"Error processing edge properties between {entity_name_label_source} "
+                            f"and {entity_name_label_target}: {str(e)}"
+                        )
+                        # Return default edge properties on error
+                        return {"weight": 0.0, "source_id": None, "target_id": None}
+
+                logger.debug(
+                    f"{inspect.currentframe().f_code.co_name}: No edge found between {entity_name_label_source} and {entity_name_label_target}"
+                )
+                # Return default edge properties when no edge found
+                return {"weight": 0.0, "source_id": None, "target_id": None}
+
+        except Exception as e:
+            logger.error(
+                f"Error in get_edge between {source_node_id} and {target_node_id}: {str(e)}"
+            )
+            # Return default edge properties on error
+            return {"weight": 0.0, "source_id": None, "target_id": None}
 
     async def get_node_edges(self, source_node_id: str) -> List[Tuple[str, str]]:
         node_label = source_node_id.strip('"')
@@ -310,7 +372,7 @@ class Neo4JStorage(BaseGraphStorage):
             node_id: The unique identifier for the node (used as label)
             node_data: Dictionary of node properties
         """
-        label = node_id.strip('"')
+        label = await self._ensure_label(node_id)
         properties = node_data
 
         async def _do_upsert(tx: AsyncManagedTransaction):
@@ -338,6 +400,7 @@ class Neo4JStorage(BaseGraphStorage):
                 neo4jExceptions.ServiceUnavailable,
                 neo4jExceptions.TransientError,
                 neo4jExceptions.WriteServiceUnavailable,
+                neo4jExceptions.ClientError,
             )
         ),
     )
@@ -352,22 +415,23 @@ class Neo4JStorage(BaseGraphStorage):
             target_node_id (str): Label of the target node (used as identifier)
             edge_data (dict): Dictionary of properties to set on the edge
         """
-        source_node_label = source_node_id.strip('"')
+        source_label = await self._ensure_label(source_node_id)
-        target_node_label = target_node_id.strip('"')
+        target_label = await self._ensure_label(target_node_id)
         edge_properties = edge_data
 
         async def _do_upsert_edge(tx: AsyncManagedTransaction):
             query = f"""
-            MATCH (source:`{source_node_label}`)
+            MATCH (source:`{source_label}`)
             WITH source
-            MATCH (target:`{target_node_label}`)
+            MATCH (target:`{target_label}`)
             MERGE (source)-[r:DIRECTED]->(target)
             SET r += $properties
             RETURN r
             """
-            await tx.run(query, properties=edge_properties)
+            result = await tx.run(query, properties=edge_properties)
+            record = await result.single()
             logger.debug(
-                f"Upserted edge from '{source_node_label}' to '{target_node_label}' with properties: {edge_properties}"
+                f"Upserted edge from '{source_label}' to '{target_label}' with properties: {edge_properties}, result: {record['r'] if record else None}"
             )
 
         try:

lightrag/operate.py

@@ -237,25 +237,65 @@ async def _merge_edges_then_upsert(
 
     if await knowledge_graph_inst.has_edge(src_id, tgt_id):
         already_edge = await knowledge_graph_inst.get_edge(src_id, tgt_id)
-        already_weights.append(already_edge["weight"])
+        # Handle the case where get_edge returns None or missing fields
-        already_source_ids.extend(
+        if already_edge:
-            split_string_by_multi_markers(already_edge["source_id"], [GRAPH_FIELD_SEP])
+            # Get weight with default 0.0 if missing
-        )
+            if "weight" in already_edge:
-        already_description.append(already_edge["description"])
+                already_weights.append(already_edge["weight"])
-        already_keywords.extend(
+            else:
-            split_string_by_multi_markers(already_edge["keywords"], [GRAPH_FIELD_SEP])
+                logger.warning(
-        )
+                    f"Edge between {src_id} and {tgt_id} missing weight field"
+                )
+                already_weights.append(0.0)
 
+            # Get source_id with empty string default if missing or None
+            if "source_id" in already_edge and already_edge["source_id"] is not None:
+                already_source_ids.extend(
+                    split_string_by_multi_markers(
+                        already_edge["source_id"], [GRAPH_FIELD_SEP]
+                    )
+                )
+
+            # Get description with empty string default if missing or None
+            if (
+                "description" in already_edge
+                and already_edge["description"] is not None
+            ):
+                already_description.append(already_edge["description"])
+
+            # Get keywords with empty string default if missing or None
+            if "keywords" in already_edge and already_edge["keywords"] is not None:
+                already_keywords.extend(
+                    split_string_by_multi_markers(
+                        already_edge["keywords"], [GRAPH_FIELD_SEP]
+                    )
+                )
+
+    # Process edges_data with None checks
     weight = sum([dp["weight"] for dp in edges_data] + already_weights)
     description = GRAPH_FIELD_SEP.join(
-        sorted(set([dp["description"] for dp in edges_data] + already_description))
+        sorted(
+            set(
+                [dp["description"] for dp in edges_data if dp.get("description")]
+                + already_description
+            )
+        )
     )
     keywords = GRAPH_FIELD_SEP.join(
-        sorted(set([dp["keywords"] for dp in edges_data] + already_keywords))
+        sorted(
+            set(
+                [dp["keywords"] for dp in edges_data if dp.get("keywords")]
+                + already_keywords
+            )
+        )
     )
     source_id = GRAPH_FIELD_SEP.join(
-        set([dp["source_id"] for dp in edges_data] + already_source_ids)
+        set(
+            [dp["source_id"] for dp in edges_data if dp.get("source_id")]
+            + already_source_ids
+        )
     )
+
     for need_insert_id in [src_id, tgt_id]:
         if not (await knowledge_graph_inst.has_node(need_insert_id)):
             await knowledge_graph_inst.upsert_node(