fix: optimize message scan sql

api/models/model.py

@@ -1038,7 +1038,6 @@ class Message(Base):
         Index("message_end_user_idx", "app_id", "from_source", "from_end_user_id"),
         Index("message_account_idx", "app_id", "from_source", "from_account_id"),
         Index("message_workflow_run_id_idx", "conversation_id", "workflow_run_id"),
-        Index("message_created_at_idx", "created_at"),
         Index("message_app_mode_idx", "app_mode"),
         Index("message_created_at_id_idx", "created_at", "id"),
     )

api/services/retention/conversation/messages_clean_service.py

@@ -6,7 +6,7 @@ import time
 from collections.abc import Sequence
 from typing import cast
 
-from sqlalchemy import delete, select
+from sqlalchemy import delete, select, tuple_
 from sqlalchemy.engine import CursorResult
 from sqlalchemy.orm import Session
 
@@ -215,13 +215,9 @@ class MessagesCleanService:
                     msg_stmt = msg_stmt.where(Message.created_at >= self._start_from)
 
                 # Apply cursor condition: (created_at, id) > (last_created_at, last_message_id)
-                # This translates to:
-                #   created_at > last_created_at OR (created_at = last_created_at AND id > last_message_id)
                 if _cursor:
-                    # Continuing from previous batch
                     msg_stmt = msg_stmt.where(
-                        (Message.created_at > _cursor[0])
-                        | ((Message.created_at == _cursor[0]) & (Message.id > _cursor[1]))
+                        tuple_(Message.created_at, Message.id) > tuple_(_cursor[0], _cursor[1])
                     )
 
                 raw_messages = list(session.execute(msg_stmt).all())