咨询：LangGraph当前是否提供MongoDB检查点类？

目前LangGraph官方并未提供基于MongoDB的原生检查点类，你提到的langchain_postgres.checkpoint.PostgresCheckpoint（PostgreSQL检查点）和langgraph.checkpoint.sqlite.SqliteSaver（SQLite检查点）是官方仅有的SQL类检查点实现。

如果需要将MongoDB作为LangGraph的检查点存储，可通过以下方式实现：

• 自定义检查点类：基于LangGraph的BaseCheckpointSaver抽象类，实现核心方法对接MongoDB的CRUD操作
• 适配LangChain组件：利用langchain_mongodb中的存储工具，封装为符合LangGraph检查点接口的类

自定义MongoDB检查点类示例 #

from langgraph.checkpoint.base import BaseCheckpointSaver, Checkpoint, CheckpointMetadata
from pymongo import MongoClient
from typing import Optional, dict, list, tuple

class MongoDBSaver(BaseCheckpointSaver):
    def __init__(self, connection_string: str, db_name: str, collection_name: str = "langgraph_checkpoints"):
        self.client = MongoClient(connection_string)
        self.collection = self.client[db_name][collection_name]

    def get(self, config: dict) -> Optional[Checkpoint]:
        doc = self.collection.find_one({"config": config})
        return Checkpoint(**doc["checkpoint"]) if doc else None

    def put(self, config: dict, checkpoint: Checkpoint, metadata: Optional[CheckpointMetadata] = None) -> None:
        update_data = {
            "checkpoint": checkpoint.dict(),
            "metadata": metadata.dict() if metadata else {}
        }
        self.collection.update_one(
            {"config": config},
            {"$set": update_data},
            upsert=True
        )

    def list(self, config: Optional[dict] = None, limit: Optional[int] = None) -> list[tuple[Checkpoint, CheckpointMetadata]]:
        query = {} if config is None else {"config": config}
        cursor = self.collection.find(query)
        if limit:
            cursor = cursor.limit(limit)
        return [
            (Checkpoint(**doc["checkpoint"]), CheckpointMetadata(**doc["metadata"]))
            for doc in cursor
        ]

内容的提问来源于stack exchange，提问作者JCm