fix: close session before doing long latency operation (#22306)

api/core/rag/datasource/retrieval_service.py

@@ -3,7 +3,7 @@ from concurrent.futures import ThreadPoolExecutor
 from typing import Optional
 
 from flask import Flask, current_app
-from sqlalchemy.orm import load_only
+from sqlalchemy.orm import Session, load_only
 
 from configs import dify_config
 from core.rag.data_post_processor.data_post_processor import DataPostProcessor
@@ -144,7 +144,8 @@ class RetrievalService:
 
     @classmethod
     def _get_dataset(cls, dataset_id: str) -> Optional[Dataset]:
-        return db.session.query(Dataset).filter(Dataset.id == dataset_id).first()
+        with Session(db.engine) as session:
+            return session.query(Dataset).filter(Dataset.id == dataset_id).first()
 
     @classmethod
     def keyword_search(