perf: decrease db query (#29837)

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

api/core/app/task_pipeline/easy_ui_based_generate_task_pipeline.py

@@ -342,9 +342,11 @@ class EasyUIBasedGenerateTaskPipeline(BasedGenerateTaskPipeline):
                 self._task_state.llm_result.message.content = current_content
 
                 if isinstance(event, QueueLLMChunkEvent):
+                    event_type = self._message_cycle_manager.get_message_event_type(message_id=self._message_id)
                     yield self._message_cycle_manager.message_to_stream_response(
                         answer=cast(str, delta_text),
                         message_id=self._message_id,
+                        event_type=event_type,
                     )
                 else:
                     yield self._agent_message_to_stream_response(

api/core/app/task_pipeline/message_cycle_manager.py

@@ -5,7 +5,7 @@ from threading import Thread
 from typing import Union
 
 from flask import Flask, current_app
-from sqlalchemy import select
+from sqlalchemy import exists, select
 from sqlalchemy.orm import Session
 
 from configs import dify_config
@@ -54,6 +54,20 @@ class MessageCycleManager:
     ):
         self._application_generate_entity = application_generate_entity
         self._task_state = task_state
+        self._message_has_file: set[str] = set()
+
+    def get_message_event_type(self, message_id: str) -> StreamEvent:
+        if message_id in self._message_has_file:
+            return StreamEvent.MESSAGE_FILE
+
+        with Session(db.engine, expire_on_commit=False) as session:
+            has_file = session.query(exists().where(MessageFile.message_id == message_id)).scalar()
+
+        if has_file:
+            self._message_has_file.add(message_id)
+            return StreamEvent.MESSAGE_FILE
+
+        return StreamEvent.MESSAGE
 
     def generate_conversation_name(self, *, conversation_id: str, query: str) -> Thread | None:
         """
@@ -214,7 +228,11 @@ class MessageCycleManager:
         return None
 
     def message_to_stream_response(
-        self, answer: str, message_id: str, from_variable_selector: list[str] | None = None
+        self,
+        answer: str,
+        message_id: str,
+        from_variable_selector: list[str] | None = None,
+        event_type: StreamEvent | None = None,
     ) -> MessageStreamResponse:
         """
         Message to stream response.
@@ -222,16 +240,12 @@ class MessageCycleManager:
         :param message_id: message id
         :return:
         """
-        with Session(db.engine, expire_on_commit=False) as session:
-            message_file = session.scalar(select(MessageFile).where(MessageFile.id == message_id))
-        event_type = StreamEvent.MESSAGE_FILE if message_file else StreamEvent.MESSAGE
-
         return MessageStreamResponse(
             task_id=self._application_generate_entity.task_id,
             id=message_id,
             answer=answer,
             from_variable_selector=from_variable_selector,
-            event=event_type,
+            event=event_type or StreamEvent.MESSAGE,
         )
 
     def message_replace_to_stream_response(self, answer: str, reason: str = "") -> MessageReplaceStreamResponse: