LightRAG/lightrag/kg/neo4j_impl.py

import inspect
import os
import re
from dataclasses import dataclass
from typing import Any, final
import numpy as np
import configparser


from tenacity import (
    retry,
    stop_after_attempt,
    wait_exponential,
    retry_if_exception_type,
)

import logging
from ..utils import logger
from ..base import BaseGraphStorage
from ..types import KnowledgeGraph, KnowledgeGraphNode, KnowledgeGraphEdge
import pipmaster as pm

if not pm.is_installed("neo4j"):
    pm.install("neo4j")

from neo4j import (  # type: ignore
    AsyncGraphDatabase,
    exceptions as neo4jExceptions,
    AsyncDriver,
    AsyncManagedTransaction,
)

config = configparser.ConfigParser()
config.read("config.ini", "utf-8")

# Get maximum number of graph nodes from environment variable, default is 1000
MAX_GRAPH_NODES = int(os.getenv("MAX_GRAPH_NODES", 1000))

# Set neo4j logger level to ERROR to suppress warning logs
logging.getLogger("neo4j").setLevel(logging.ERROR)


@final
@dataclass
class Neo4JStorage(BaseGraphStorage):
    def __init__(self, namespace, global_config, embedding_func):
        super().__init__(
            namespace=namespace,
            global_config=global_config,
            embedding_func=embedding_func,
        )
        self._driver = None

    def __post_init__(self):
        self._node_embed_algorithms = {
            "node2vec": self._node2vec_embed,
        }

    async def initialize(self):
        URI = os.environ.get("NEO4J_URI", config.get("neo4j", "uri", fallback=None))
        USERNAME = os.environ.get(
            "NEO4J_USERNAME", config.get("neo4j", "username", fallback=None)
        )
        PASSWORD = os.environ.get(
            "NEO4J_PASSWORD", config.get("neo4j", "password", fallback=None)
        )
        MAX_CONNECTION_POOL_SIZE = int(
            os.environ.get(
                "NEO4J_MAX_CONNECTION_POOL_SIZE",
                config.get("neo4j", "connection_pool_size", fallback=50),
            )
        )
        CONNECTION_TIMEOUT = float(
            os.environ.get(
                "NEO4J_CONNECTION_TIMEOUT",
                config.get("neo4j", "connection_timeout", fallback=30.0),
            ),
        )
        CONNECTION_ACQUISITION_TIMEOUT = float(
            os.environ.get(
                "NEO4J_CONNECTION_ACQUISITION_TIMEOUT",
                config.get("neo4j", "connection_acquisition_timeout", fallback=30.0),
            ),
        )
        MAX_TRANSACTION_RETRY_TIME = float(
            os.environ.get(
                "NEO4J_MAX_TRANSACTION_RETRY_TIME",
                config.get("neo4j", "max_transaction_retry_time", fallback=30.0),
            ),
        )
        DATABASE = os.environ.get(
            "NEO4J_DATABASE", re.sub(r"[^a-zA-Z0-9-]", "-", self.namespace)
        )

        self._driver: AsyncDriver = AsyncGraphDatabase.driver(
            URI,
            auth=(USERNAME, PASSWORD),
            max_connection_pool_size=MAX_CONNECTION_POOL_SIZE,
            connection_timeout=CONNECTION_TIMEOUT,
            connection_acquisition_timeout=CONNECTION_ACQUISITION_TIMEOUT,
            max_transaction_retry_time=MAX_TRANSACTION_RETRY_TIME,
        )

        # Try to connect to the database and create it if it doesn't exist
        for database in (DATABASE, None):
            self._DATABASE = database
            connected = False

            try:
                async with self._driver.session(database=database) as session:
                    try:
                        result = await session.run("MATCH (n) RETURN n LIMIT 0")
                        await result.consume()  # Ensure result is consumed
                        logger.info(f"Connected to {database} at {URI}")
                        connected = True
                    except neo4jExceptions.ServiceUnavailable as e:
                        logger.error(
                            f"{database} at {URI} is not available".capitalize()
                        )
                        raise e
            except neo4jExceptions.AuthError as e:
                logger.error(f"Authentication failed for {database} at {URI}")
                raise e
            except neo4jExceptions.ClientError as e:
                if e.code == "Neo.ClientError.Database.DatabaseNotFound":
                    logger.info(
                        f"{database} at {URI} not found. Try to create specified database.".capitalize()
                    )
                    try:
                        async with self._driver.session() as session:
                            result = await session.run(
                                f"CREATE DATABASE `{database}` IF NOT EXISTS"
                            )
                            await result.consume()  # Ensure result is consumed
                            logger.info(f"{database} at {URI} created".capitalize())
                            connected = True
                    except (
                        neo4jExceptions.ClientError,
                        neo4jExceptions.DatabaseError,
                    ) as e:
                        if (
                            e.code
                            == "Neo.ClientError.Statement.UnsupportedAdministrationCommand"
                        ) or (e.code == "Neo.DatabaseError.Statement.ExecutionFailed"):
                            if database is not None:
                                logger.warning(
                                    "This Neo4j instance does not support creating databases. Try to use Neo4j Desktop/Enterprise version or DozerDB instead. Fallback to use the default database."
                                )
                        if database is None:
                            logger.error(f"Failed to create {database} at {URI}")
                            raise e

            if connected:
                # Create index for base nodes on entity_id if it doesn't exist
                try:
                    async with self._driver.session(database=database) as session:
                        # Check if index exists first
                        check_query = """
                        CALL db.indexes() YIELD name, labelsOrTypes, properties
                        WHERE labelsOrTypes = ['base'] AND properties = ['entity_id']
                        RETURN count(*) > 0 AS exists
                        """
                        try:
                            check_result = await session.run(check_query)
                            record = await check_result.single()
                            await check_result.consume()

                            index_exists = record and record.get("exists", False)

                            if not index_exists:
                                # Create index only if it doesn't exist
                                result = await session.run(
                                    "CREATE INDEX FOR (n:base) ON (n.entity_id)"
                                )
                                await result.consume()
                                logger.info(
                                    f"Created index for base nodes on entity_id in {database}"
                                )
                        except Exception:
                            # Fallback if db.indexes() is not supported in this Neo4j version
                            result = await session.run(
                                "CREATE INDEX IF NOT EXISTS FOR (n:base) ON (n.entity_id)"
                            )
                            await result.consume()
                except Exception as e:
                    logger.warning(f"Failed to create index: {str(e)}")
                break

    async def finalize(self):
        """Close the Neo4j driver and release all resources"""
        if self._driver:
            await self._driver.close()
            self._driver = None

    async def __aexit__(self, exc_type, exc, tb):
        """Ensure driver is closed when context manager exits"""
        await self.finalize()

    async def index_done_callback(self) -> None:
        # Noe4J handles persistence automatically
        pass

    async def has_node(self, node_id: str) -> bool:
        """
        Check if a node with the given label exists in the database

        Args:
            node_id: Label of the node to check

        Returns:
            bool: True if node exists, False otherwise

        Raises:
            ValueError: If node_id is invalid
            Exception: If there is an error executing the query
        """
        async with self._driver.session(
            database=self._DATABASE, default_access_mode="READ"
        ) as session:
            try:
                query = "MATCH (n:base {entity_id: $entity_id}) RETURN count(n) > 0 AS node_exists"
                result = await session.run(query, entity_id=node_id)
                single_result = await result.single()
                await result.consume()  # Ensure result is fully consumed
                return single_result["node_exists"]
            except Exception as e:
                logger.error(f"Error checking node existence for {node_id}: {str(e)}")
                await result.consume()  # Ensure results are consumed even on error
                raise

    async def has_edge(self, source_node_id: str, target_node_id: str) -> bool:
        """
        Check if an edge exists between two nodes

        Args:
            source_node_id: Label of the source node
            target_node_id: Label of the target node

        Returns:
            bool: True if edge exists, False otherwise

        Raises:
            ValueError: If either node_id is invalid
            Exception: If there is an error executing the query
        """
        async with self._driver.session(
            database=self._DATABASE, default_access_mode="READ"
        ) as session:
            try:
                query = (
                    "MATCH (a:base {entity_id: $source_entity_id})-[r]-(b:base {entity_id: $target_entity_id}) "
                    "RETURN COUNT(r) > 0 AS edgeExists"
                )
                result = await session.run(
                    query,
                    source_entity_id=source_node_id,
                    target_entity_id=target_node_id,
                )
                single_result = await result.single()
                await result.consume()  # Ensure result is fully consumed
                return single_result["edgeExists"]
            except Exception as e:
                logger.error(
                    f"Error checking edge existence between {source_node_id} and {target_node_id}: {str(e)}"
                )
                await result.consume()  # Ensure results are consumed even on error
                raise

    async def get_node(self, node_id: str) -> dict[str, str] | None:
        """Get node by its label identifier, return only node properties

        Args:
            node_id: The node label to look up

        Returns:
            dict: Node properties if found
            None: If node not found

        Raises:
            ValueError: If node_id is invalid
            Exception: If there is an error executing the query
        """
        async with self._driver.session(
            database=self._DATABASE, default_access_mode="READ"
        ) as session:
            try:
                query = "MATCH (n:base {entity_id: $entity_id}) RETURN n"
                result = await session.run(query, entity_id=node_id)
                try:
                    records = await result.fetch(
                        2
                    )  # Get 2 records for duplication check

                    if len(records) > 1:
                        logger.warning(
                            f"Multiple nodes found with label '{node_id}'. Using first node."
                        )
                    if records:
                        node = records[0]["n"]
                        node_dict = dict(node)
                        # Remove base label from labels list if it exists
                        if "labels" in node_dict:
                            node_dict["labels"] = [
                                label
                                for label in node_dict["labels"]
                                if label != "base"
                            ]
                        logger.debug(f"Neo4j query node {query} return: {node_dict}")
                        return node_dict
                    return None
                finally:
                    await result.consume()  # Ensure result is fully consumed
            except Exception as e:
                logger.error(f"Error getting node for {node_id}: {str(e)}")
                raise

    async def node_degree(self, node_id: str) -> int:
        """Get the degree (number of relationships) of a node with the given label.
        If multiple nodes have the same label, returns the degree of the first node.
        If no node is found, returns 0.

        Args:
            node_id: The label of the node

        Returns:
            int: The number of relationships the node has, or 0 if no node found

        Raises:
            ValueError: If node_id is invalid
            Exception: If there is an error executing the query
        """
        async with self._driver.session(
            database=self._DATABASE, default_access_mode="READ"
        ) as session:
            try:
                query = """
                    MATCH (n:base {entity_id: $entity_id})
                    OPTIONAL MATCH (n)-[r]-()
                    RETURN COUNT(r) AS degree
                """
                result = await session.run(query, entity_id=node_id)
                try:
                    record = await result.single()

                    if not record:
                        logger.warning(f"No node found with label '{node_id}'")
                        return 0

                    degree = record["degree"]
                    logger.debug(
                        f"Neo4j query node degree for {node_id} return: {degree}"
                    )
                    return degree
                finally:
                    await result.consume()  # Ensure result is fully consumed
            except Exception as e:
                logger.error(f"Error getting node degree for {node_id}: {str(e)}")
                raise

    async def edge_degree(self, src_id: str, tgt_id: str) -> int:
        """Get the total degree (sum of relationships) of two nodes.

        Args:
            src_id: Label of the source node
            tgt_id: Label of the target node

        Returns:
            int: Sum of the degrees of both nodes
        """
        src_degree = await self.node_degree(src_id)
        trg_degree = await self.node_degree(tgt_id)

        # Convert None to 0 for addition
        src_degree = 0 if src_degree is None else src_degree
        trg_degree = 0 if trg_degree is None else trg_degree

        degrees = int(src_degree) + int(trg_degree)
        return degrees

    async def get_edge(
        self, source_node_id: str, target_node_id: str
    ) -> dict[str, str] | None:
        """Get edge properties between two nodes.

        Args:
            source_node_id: Label of the source node
            target_node_id: Label of the target node

        Returns:
            dict: Edge properties if found, default properties if not found or on error

        Raises:
            ValueError: If either node_id is invalid
            Exception: If there is an error executing the query
        """
        try:
            async with self._driver.session(
                database=self._DATABASE, default_access_mode="READ"
            ) as session:
                query = """
                MATCH (start:base {entity_id: $source_entity_id})-[r]-(end:base {entity_id: $target_entity_id})
                RETURN properties(r) as edge_properties
                """
                result = await session.run(
                    query,
                    source_entity_id=source_node_id,
                    target_entity_id=target_node_id,
                )
                try:
                    records = await result.fetch(2)

                    if len(records) > 1:
                        logger.warning(
                            f"Multiple edges found between '{source_node_id}' and '{target_node_id}'. Using first edge."
                        )
                    if records:
                        try:
                            edge_result = dict(records[0]["edge_properties"])
                            logger.debug(f"Result: {edge_result}")
                            # Ensure required keys exist with defaults
                            required_keys = {
                                "weight": 0.0,
                                "source_id": None,
                                "description": None,
                                "keywords": None,
                            }
                            for key, default_value in required_keys.items():
                                if key not in edge_result:
                                    edge_result[key] = default_value
                                    logger.warning(
                                        f"Edge between {source_node_id} and {target_node_id} "
                                        f"missing {key}, using default: {default_value}"
                                    )

                            logger.debug(
                                f"{inspect.currentframe().f_code.co_name}:query:{query}:result:{edge_result}"
                            )
                            return edge_result
                        except (KeyError, TypeError, ValueError) as e:
                            logger.error(
                                f"Error processing edge properties between {source_node_id} "
                                f"and {target_node_id}: {str(e)}"
                            )
                            # Return default edge properties on error
                            return {
                                "weight": 0.0,
                                "source_id": None,
                                "description": None,
                                "keywords": None,
                            }

                    logger.debug(
                        f"{inspect.currentframe().f_code.co_name}: No edge found between {source_node_id} and {target_node_id}"
                    )
                    # Return None when no edge found
                    return None
                finally:
                    await result.consume()  # Ensure result is fully consumed

        except Exception as e:
            logger.error(
                f"Error in get_edge between {source_node_id} and {target_node_id}: {str(e)}"
            )
            raise

    async def get_node_edges(self, source_node_id: str) -> list[tuple[str, str]] | None:
        """Retrieves all edges (relationships) for a particular node identified by its label.

        Args:
            source_node_id: Label of the node to get edges for

        Returns:
            list[tuple[str, str]]: List of (source_label, target_label) tuples representing edges
            None: If no edges found

        Raises:
            ValueError: If source_node_id is invalid
            Exception: If there is an error executing the query
        """
        try:
            async with self._driver.session(
                database=self._DATABASE, default_access_mode="READ"
            ) as session:
                try:
                    query = """MATCH (n:base {entity_id: $entity_id})
                            OPTIONAL MATCH (n)-[r]-(connected:base)
                            WHERE connected.entity_id IS NOT NULL
                            RETURN n, r, connected"""
                    results = await session.run(query, entity_id=source_node_id)

                    edges = []
                    async for record in results:
                        source_node = record["n"]
                        connected_node = record["connected"]

                        # Skip if either node is None
                        if not source_node or not connected_node:
                            continue

                        source_label = (
                            source_node.get("entity_id")
                            if source_node.get("entity_id")
                            else None
                        )
                        target_label = (
                            connected_node.get("entity_id")
                            if connected_node.get("entity_id")
                            else None
                        )

                        if source_label and target_label:
                            edges.append((source_label, target_label))

                    await results.consume()  # Ensure results are consumed
                    return edges
                except Exception as e:
                    logger.error(
                        f"Error getting edges for node {source_node_id}: {str(e)}"
                    )
                    await results.consume()  # Ensure results are consumed even on error
                    raise
        except Exception as e:
            logger.error(f"Error in get_node_edges for {source_node_id}: {str(e)}")
            raise

    @retry(
        stop=stop_after_attempt(3),
        wait=wait_exponential(multiplier=1, min=4, max=10),
        retry=retry_if_exception_type(
            (
                neo4jExceptions.ServiceUnavailable,
                neo4jExceptions.TransientError,
                neo4jExceptions.WriteServiceUnavailable,
                neo4jExceptions.ClientError,
            )
        ),
    )
    async def upsert_node(self, node_id: str, node_data: dict[str, str]) -> None:
        """
        Upsert a node in the Neo4j database.

        Args:
            node_id: The unique identifier for the node (used as label)
            node_data: Dictionary of node properties
        """
        properties = node_data
        entity_type = properties["entity_type"]
        if "entity_id" not in properties:
            raise ValueError("Neo4j: node properties must contain an 'entity_id' field")

        try:
            async with self._driver.session(database=self._DATABASE) as session:

                async def execute_upsert(tx: AsyncManagedTransaction):
                    query = (
                        """
                    MERGE (n:base {entity_id: $entity_id})
                    SET n += $properties
                    SET n:`%s`
                    """
                        % entity_type
                    )
                    result = await tx.run(
                        query, entity_id=node_id, properties=properties
                    )
                    logger.debug(
                        f"Upserted node with entity_id '{node_id}' and properties: {properties}"
                    )
                    await result.consume()  # Ensure result is fully consumed

                await session.execute_write(execute_upsert)
        except Exception as e:
            logger.error(f"Error during upsert: {str(e)}")
            raise

    @retry(
        stop=stop_after_attempt(3),
        wait=wait_exponential(multiplier=1, min=4, max=10),
        retry=retry_if_exception_type(
            (
                neo4jExceptions.ServiceUnavailable,
                neo4jExceptions.TransientError,
                neo4jExceptions.WriteServiceUnavailable,
                neo4jExceptions.ClientError,
            )
        ),
    )
    async def upsert_edge(
        self, source_node_id: str, target_node_id: str, edge_data: dict[str, str]
    ) -> None:
        """
        Upsert an edge and its properties between two nodes identified by their labels.
        Ensures both source and target nodes exist and are unique before creating the edge.
        Uses entity_id property to uniquely identify nodes.

        Args:
            source_node_id (str): Label of the source node (used as identifier)
            target_node_id (str): Label of the target node (used as identifier)
            edge_data (dict): Dictionary of properties to set on the edge

        Raises:
            ValueError: If either source or target node does not exist or is not unique
        """
        try:
            edge_properties = edge_data
            async with self._driver.session(database=self._DATABASE) as session:

                async def execute_upsert(tx: AsyncManagedTransaction):
                    query = """
                    MATCH (source:base {entity_id: $source_entity_id})
                    WITH source
                    MATCH (target:base {entity_id: $target_entity_id})
                    MERGE (source)-[r:DIRECTED]-(target)
                    SET r += $properties
                    RETURN r, source, target
                    """
                    result = await tx.run(
                        query,
                        source_entity_id=source_node_id,
                        target_entity_id=target_node_id,
                        properties=edge_properties,
                    )
                    try:
                        records = await result.fetch(2)
                        if records:
                            logger.debug(
                                f"Upserted edge from '{source_node_id}' to '{target_node_id}'"
                                f"with properties: {edge_properties}"
                            )
                    finally:
                        await result.consume()  # Ensure result is consumed

                await session.execute_write(execute_upsert)
        except Exception as e:
            logger.error(f"Error during edge upsert: {str(e)}")
            raise

    async def _node2vec_embed(self):
        print("Implemented but never called.")

    async def get_knowledge_graph(
        self,
        node_label: str,
        max_depth: int = 3,
        max_nodes: int = MAX_GRAPH_NODES,
    ) -> KnowledgeGraph:
        """
        Retrieve a connected subgraph of nodes where the label includes the specified `node_label`.

        Args:
            node_label: Label of the starting node, * means all nodes
            max_depth: Maximum depth of the subgraph, Defaults to 3
            max_nodes: Maxiumu nodes to return by BFS, Defaults to 1000

        Returns:
            KnowledgeGraph object containing nodes and edges, with an is_truncated flag
            indicating whether the graph was truncated due to max_nodes limit
        """
        result = KnowledgeGraph()
        seen_nodes = set()
        seen_edges = set()

        async with self._driver.session(
            database=self._DATABASE, default_access_mode="READ"
        ) as session:
            try:
                if node_label == "*":
                    # First check total node count to determine if graph is truncated
                    count_query = "MATCH (n) RETURN count(n) as total"
                    count_result = None
                    try:
                        count_result = await session.run(count_query)
                        count_record = await count_result.single()

                        if count_record and count_record["total"] > max_nodes:
                            result.is_truncated = True
                            logger.info(
                                f"Graph truncated: {count_record['total']} nodes found, limited to {max_nodes}"
                            )
                    finally:
                        if count_result:
                            await count_result.consume()

                    # Run main query to get nodes with highest degree
                    main_query = """
                    MATCH (n)
                    OPTIONAL MATCH (n)-[r]-()
                    WITH n, COALESCE(count(r), 0) AS degree
                    ORDER BY degree DESC
                    LIMIT $max_nodes
                    WITH collect({node: n}) AS filtered_nodes
                    UNWIND filtered_nodes AS node_info
                    WITH collect(node_info.node) AS kept_nodes, filtered_nodes
                    OPTIONAL MATCH (a)-[r]-(b)
                    WHERE a IN kept_nodes AND b IN kept_nodes
                    RETURN filtered_nodes AS node_info,
                           collect(DISTINCT r) AS relationships
                    """
                    result_set = None
                    try:
                        result_set = await session.run(
                            main_query,
                            {"max_nodes": max_nodes},
                        )
                        record = await result_set.single()
                    finally:
                        if result_set:
                            await result_set.consume()

                else:
                    # return await self._robust_fallback(node_label, max_depth, max_nodes)
                    # First try without limit to check if we need to truncate
                    full_query = """
                    MATCH (start)
                    WHERE start.entity_id = $entity_id
                    WITH start
                    CALL apoc.path.subgraphAll(start, {
                        relationshipFilter: '',
                        minLevel: 0,
                        maxLevel: $max_depth,
                        bfs: true
                    })
                    YIELD nodes, relationships
                    WITH nodes, relationships, size(nodes) AS total_nodes
                    UNWIND nodes AS node
                    WITH collect({node: node}) AS node_info, relationships, total_nodes
                    RETURN node_info, relationships, total_nodes
                    """

                    # Try to get full result
                    full_result = None
                    try:
                        full_result = await session.run(
                            full_query,
                            {
                                "entity_id": node_label,
                                "max_depth": max_depth,
                            },
                        )
                        full_record = await full_result.single()

                        # If no record found, return empty KnowledgeGraph
                        if not full_record:
                            logger.debug(f"No nodes found for entity_id: {node_label}")
                            return result

                        # If record found, check node count
                        total_nodes = full_record["total_nodes"]

                        if total_nodes <= max_nodes:
                            # If node count is within limit, use full result directly
                            logger.debug(
                                f"Using full result with {total_nodes} nodes (no truncation needed)"
                            )
                            record = full_record
                        else:
                            # If node count exceeds limit, set truncated flag and run limited query
                            result.is_truncated = True
                            logger.info(
                                f"Graph truncated: {total_nodes} nodes found, breadth-first search limited to {max_nodes}"
                            )

                            # Run limited query
                            limited_query = """
                            MATCH (start)
                            WHERE start.entity_id = $entity_id
                            WITH start
                            CALL apoc.path.subgraphAll(start, {
                                relationshipFilter: '',
                                minLevel: 0,
                                maxLevel: $max_depth,
                                limit: $max_nodes,
                                bfs: true
                            })
                            YIELD nodes, relationships
                            UNWIND nodes AS node
                            WITH collect({node: node}) AS node_info, relationships
                            RETURN node_info, relationships
                            """
                            result_set = None
                            try:
                                result_set = await session.run(
                                    limited_query,
                                    {
                                        "entity_id": node_label,
                                        "max_depth": max_depth,
                                        "max_nodes": max_nodes,
                                    },
                                )
                                record = await result_set.single()
                            finally:
                                if result_set:
                                    await result_set.consume()
                    finally:
                        if full_result:
                            await full_result.consume()

                if record:
                    # Handle nodes (compatible with multi-label cases)
                    for node_info in record["node_info"]:
                        node = node_info["node"]
                        node_id = node.id
                        if node_id not in seen_nodes:
                            result.nodes.append(
                                KnowledgeGraphNode(
                                    id=f"{node_id}",
                                    labels=[node.get("entity_id")],
                                    properties=dict(node),
                                )
                            )
                            seen_nodes.add(node_id)

                    # Handle relationships (including direction information)
                    for rel in record["relationships"]:
                        edge_id = rel.id
                        if edge_id not in seen_edges:
                            start = rel.start_node
                            end = rel.end_node
                            result.edges.append(
                                KnowledgeGraphEdge(
                                    id=f"{edge_id}",
                                    type=rel.type,
                                    source=f"{start.id}",
                                    target=f"{end.id}",
                                    properties=dict(rel),
                                )
                            )
                            seen_edges.add(edge_id)

                    logger.info(
                        f"Subgraph query successful | Node count: {len(result.nodes)} | Edge count: {len(result.edges)}"
                    )

            except neo4jExceptions.ClientError as e:
                logger.warning(f"APOC plugin error: {str(e)}")
                if node_label != "*":
                    logger.warning(
                        "Neo4j: falling back to basic Cypher recursive search..."
                    )
                    return await self._robust_fallback(node_label, max_depth, max_nodes)
                else:
                    logger.warning(
                        "Neo4j: APOC plugin error with wildcard query, returning empty result"
                    )

        return result

    async def _robust_fallback(
        self, node_label: str, max_depth: int, max_nodes: int
    ) -> KnowledgeGraph:
        """
        Fallback implementation when APOC plugin is not available or incompatible.
        This method implements the same functionality as get_knowledge_graph but uses
        only basic Cypher queries and true breadth-first traversal instead of APOC procedures.
        """
        from collections import deque

        result = KnowledgeGraph()
        visited_nodes = set()
        visited_edges = set()
        visited_edge_pairs = set()  # 用于跟踪已处理的边对(排序后的source_id, target_id)

        # Get the starting node's data
        async with self._driver.session(
            database=self._DATABASE, default_access_mode="READ"
        ) as session:
            query = """
            MATCH (n:base {entity_id: $entity_id})
            RETURN id(n) as node_id, n
            """
            node_result = await session.run(query, entity_id=node_label)
            try:
                node_record = await node_result.single()
                if not node_record:
                    return result

                # Create initial KnowledgeGraphNode
                start_node = KnowledgeGraphNode(
                    id=f"{node_record['n'].get('entity_id')}",
                    labels=[node_record["n"].get("entity_id")],
                    properties=dict(node_record["n"]._properties),
                )
            finally:
                await node_result.consume()  # Ensure results are consumed

        # Initialize queue for BFS with (node, edge, depth) tuples
        # edge is None for the starting node
        queue = deque([(start_node, None, 0)])

        # True BFS implementation using a queue
        while queue and len(visited_nodes) < max_nodes:
            # Dequeue the next node to process
            current_node, current_edge, current_depth = queue.popleft()

            # Skip if already visited or exceeds max depth
            if current_node.id in visited_nodes:
                continue

            if current_depth > max_depth:
                logger.debug(
                    f"Skipping node at depth {current_depth} (max_depth: {max_depth})"
                )
                continue

            # Add current node to result
            result.nodes.append(current_node)
            visited_nodes.add(current_node.id)

            # Add edge to result if it exists and not already added
            if current_edge and current_edge.id not in visited_edges:
                result.edges.append(current_edge)
                visited_edges.add(current_edge.id)

            # Stop if we've reached the node limit
            if len(visited_nodes) >= max_nodes:
                result.is_truncated = True
                logger.info(
                    f"Graph truncated: breadth-first search limited to: {max_nodes} nodes"
                )
                break

            # Get all edges and target nodes for the current node (even at max_depth)
            async with self._driver.session(
                database=self._DATABASE, default_access_mode="READ"
            ) as session:
                query = """
                MATCH (a:base {entity_id: $entity_id})-[r]-(b)
                WITH r, b, id(r) as edge_id, id(b) as target_id
                RETURN r, b, edge_id, target_id
                """
                results = await session.run(query, entity_id=current_node.id)

                # Get all records and release database connection
                records = await results.fetch(1000)  # Max neighbor nodes we can handle
                await results.consume()  # Ensure results are consumed

                # Process all neighbors - capture all edges but only queue unvisited nodes
                for record in records:
                    rel = record["r"]
                    edge_id = str(record["edge_id"])

                    if edge_id not in visited_edges:
                        b_node = record["b"]
                        target_id = b_node.get("entity_id")

                        if target_id:  # Only process if target node has entity_id
                            # Create KnowledgeGraphNode for target
                            target_node = KnowledgeGraphNode(
                                id=f"{target_id}",
                                labels=[target_id],
                                properties=dict(b_node._properties),
                            )

                            # Create KnowledgeGraphEdge
                            target_edge = KnowledgeGraphEdge(
                                id=f"{edge_id}",
                                type=rel.type,
                                source=f"{current_node.id}",
                                target=f"{target_id}",
                                properties=dict(rel),
                            )

                            # 对source_id和target_id进行排序，确保(A,B)和(B,A)被视为同一条边
                            sorted_pair = tuple(sorted([current_node.id, target_id]))

                            # 检查是否已存在相同的边（考虑无向性）
                            if sorted_pair not in visited_edge_pairs:
                                # 只有当目标节点已经在结果中或将被添加到结果中时，才添加边
                                if target_id in visited_nodes or (
                                    target_id not in visited_nodes
                                    and current_depth < max_depth
                                ):
                                    result.edges.append(target_edge)
                                    visited_edges.add(edge_id)
                                    visited_edge_pairs.add(sorted_pair)

                            # Only add unvisited nodes to the queue for further expansion
                            if target_id not in visited_nodes:
                                # Only add to queue if we're not at max depth yet
                                if current_depth < max_depth:
                                    # Add node to queue with incremented depth
                                    # Edge is already added to result, so we pass None as edge
                                    queue.append((target_node, None, current_depth + 1))
                                else:
                                    # At max depth, we've already added the edge but we don't add the node
                                    # This prevents adding nodes beyond max_depth to the result
                                    logger.debug(
                                        f"Node {target_id} beyond max depth {max_depth}, edge added but node not included"
                                    )
                            else:
                                # If target node already exists in result, we don't need to add it again
                                logger.debug(
                                    f"Node {target_id} already visited, edge added but node not queued"
                                )
                        else:
                            logger.warning(
                                f"Skipping edge {edge_id} due to missing entity_id on target node"
                            )

        logger.info(
            f"BFS subgraph query successful | Node count: {len(result.nodes)} | Edge count: {len(result.edges)}"
        )
        return result

    async def get_all_labels(self) -> list[str]:
        """
        Get all existing node labels in the database
        Returns:
            ["Person", "Company", ...]  # Alphabetically sorted label list
        """
        async with self._driver.session(
            database=self._DATABASE, default_access_mode="READ"
        ) as session:
            # Method 1: Direct metadata query (Available for Neo4j 4.3+)
            # query = "CALL db.labels() YIELD label RETURN label"

            # Method 2: Query compatible with older versions
            query = """
            MATCH (n:base)
            WHERE n.entity_id IS NOT NULL
            RETURN DISTINCT n.entity_id AS label
            ORDER BY label
            """
            result = await session.run(query)
            labels = []
            try:
                async for record in result:
                    labels.append(record["label"])
            finally:
                await (
                    result.consume()
                )  # Ensure results are consumed even if processing fails
            return labels

    @retry(
        stop=stop_after_attempt(3),
        wait=wait_exponential(multiplier=1, min=4, max=10),
        retry=retry_if_exception_type(
            (
                neo4jExceptions.ServiceUnavailable,
                neo4jExceptions.TransientError,
                neo4jExceptions.WriteServiceUnavailable,
                neo4jExceptions.ClientError,
            )
        ),
    )
    async def delete_node(self, node_id: str) -> None:
        """Delete a node with the specified label

        Args:
            node_id: The label of the node to delete
        """

        async def _do_delete(tx: AsyncManagedTransaction):
            query = """
            MATCH (n:base {entity_id: $entity_id})
            DETACH DELETE n
            """
            result = await tx.run(query, entity_id=node_id)
            logger.debug(f"Deleted node with label '{node_id}'")
            await result.consume()  # Ensure result is fully consumed

        try:
            async with self._driver.session(database=self._DATABASE) as session:
                await session.execute_write(_do_delete)
        except Exception as e:
            logger.error(f"Error during node deletion: {str(e)}")
            raise

    @retry(
        stop=stop_after_attempt(3),
        wait=wait_exponential(multiplier=1, min=4, max=10),
        retry=retry_if_exception_type(
            (
                neo4jExceptions.ServiceUnavailable,
                neo4jExceptions.TransientError,
                neo4jExceptions.WriteServiceUnavailable,
                neo4jExceptions.ClientError,
            )
        ),
    )
    async def remove_nodes(self, nodes: list[str]):
        """Delete multiple nodes

        Args:
            nodes: List of node labels to be deleted
        """
        for node in nodes:
            await self.delete_node(node)

    @retry(
        stop=stop_after_attempt(3),
        wait=wait_exponential(multiplier=1, min=4, max=10),
        retry=retry_if_exception_type(
            (
                neo4jExceptions.ServiceUnavailable,
                neo4jExceptions.TransientError,
                neo4jExceptions.WriteServiceUnavailable,
                neo4jExceptions.ClientError,
            )
        ),
    )
    async def remove_edges(self, edges: list[tuple[str, str]]):
        """Delete multiple edges

        Args:
            edges: List of edges to be deleted, each edge is a (source, target) tuple
        """
        for source, target in edges:

            async def _do_delete_edge(tx: AsyncManagedTransaction):
                query = """
                MATCH (source:base {entity_id: $source_entity_id})-[r]-(target:base {entity_id: $target_entity_id})
                DELETE r
                """
                result = await tx.run(
                    query, source_entity_id=source, target_entity_id=target
                )
                logger.debug(f"Deleted edge from '{source}' to '{target}'")
                await result.consume()  # Ensure result is fully consumed

            try:
                async with self._driver.session(database=self._DATABASE) as session:
                    await session.execute_write(_do_delete_edge)
            except Exception as e:
                logger.error(f"Error during edge deletion: {str(e)}")
                raise

    async def embed_nodes(
        self, algorithm: str
    ) -> tuple[np.ndarray[Any, Any], list[str]]:
        raise NotImplementedError

    async def drop(self) -> dict[str, str]:
        """Drop all data from storage and clean up resources

        This method will delete all nodes and relationships in the Neo4j database.

        Returns:
            dict[str, str]: Operation status and message
            - On success: {"status": "success", "message": "data dropped"}
            - On failure: {"status": "error", "message": "<error details>"}
        """
        try:
            async with self._driver.session(database=self._DATABASE) as session:
                # Delete all nodes and relationships
                query = "MATCH (n) DETACH DELETE n"
                result = await session.run(query)
                await result.consume()  # Ensure result is fully consumed

                logger.info(
                    f"Process {os.getpid()} drop Neo4j database {self._DATABASE}"
                )
                return {"status": "success", "message": "data dropped"}
        except Exception as e:
            logger.error(f"Error dropping Neo4j database {self._DATABASE}: {e}")
            return {"status": "error", "message": str(e)}