添加长期存储，流式检查

app/history.py

@@ -28,11 +28,14 @@ class ThreadHistoryService:
         try:
             # 查询 checkpoints 表获取用户的线程列表
             async with self.checkpointer.conn.cursor() as cur:
-                # 查询每个线程的最新 checkpoint 和创建时间
+                # 在较新的 LangGraph 版本中，AsyncPostgresSaver 创建的 checkpoints 表
+                # 没有 created_at 列，而是使用 checkpoint_id 作为时间排序依据。
+                # 我们可以直接按 thread_id 去重，并用 checkpoint_id 排序。
+                # 另外，用户的 metadata 存储在 metadata JSONB 列中。
                 query = """
                     SELECT 
                         thread_id,
-                        MAX(created_at) as last_updated
+                        MAX(checkpoint_id) as last_updated
                     FROM checkpoints
                     WHERE metadata->>'user_id' = %s
                     GROUP BY thread_id
@@ -49,17 +52,20 @@ class ThreadHistoryService:
                     # 获取该线程的状态
                     state = await self.checkpointer.aget_tuple({"configurable": {"thread_id": thread_id}})
                     
-                    if state and state.values:
-                        messages = state.values.get("messages", [])
-                        summary = self._extract_summary(messages)
-                        message_count = len([m for m in messages if hasattr(m, 'type') and m.type in ["human", "ai"]])
+                    if state and hasattr(state, 'checkpoint') and isinstance(state.checkpoint, dict):
+                        messages = state.checkpoint.get("channel_values", {}).get("messages", [])
                         
-                        threads.append({
-                            "thread_id": thread_id,
-                            "last_updated": row['last_updated'].isoformat() if row['last_updated'] else "",
-                            "summary": summary,
-                            "message_count": message_count
-                        })
+                        if messages:
+                            summary = self._extract_summary(messages)
+                            message_count = len([m for m in messages if hasattr(m, 'type') and m.type in ["human", "ai"]])
+                            
+                            threads.append({
+                                "thread_id": thread_id,
+                                # checkpoint_id 是一个类似于 uuid 的字符串，其中可能包含时间戳信息，也可以直接作为唯一标识
+                                "last_updated": row['last_updated'] if row['last_updated'] else "",
+                                "summary": summary,
+                                "message_count": message_count
+                            })
                 
                 return threads
                 
@@ -80,10 +86,13 @@ class ThreadHistoryService:
         try:
             state = await self.checkpointer.aget_tuple({"configurable": {"thread_id": thread_id}})
             
-            if state is None or not state.values:
+            if state is None:
                 return []
             
-            messages = state.values.get("messages", [])
+            messages = state.checkpoint.get("channel_values", {}).get("messages", []) if hasattr(state, 'checkpoint') and isinstance(state.checkpoint, dict) else []
+            
+            if not messages:
+                return []
             
             # 转换 LangChain 消息对象为字典
             result = []