fix: speed up chat detail pagination

ai_knowledge_base_v2/apps/backend/app/api/admin_records.py

@@ -80,6 +80,28 @@ def export_chats(
     )
 
 
+@router.get("/chat/{session_id}/messages")
+def chat_messages(
+    session_id: int,
+    page: int = Query(default=1, ge=1),
+    pageSize: int = Query(default=20, ge=10, le=100),
+    db: Session = Depends(get_db),
+    current_admin: Admin = Depends(get_current_admin),
+) -> dict:
+    exists_session = db.scalar(select(ChatSession.id).where(ChatSession.id == session_id))
+    if exists_session is None:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="会话不存在")
+    message_query = select(ChatMessage).where(ChatMessage.session_id == session_id)
+    total = db.scalar(select(func.count()).select_from(message_query.subquery())) or 0
+    messages = db.scalars(
+        message_query
+        .order_by(ChatMessage.created_at.asc(), ChatMessage.id.asc())
+        .offset((page - 1) * pageSize)
+        .limit(pageSize)
+    ).all()
+    return api_success(page_result([_message_dict(item) for item in messages], total=total, page=page, page_size=pageSize))
+
+
 @router.get("/chat/{session_id}")
 def chat_detail(
     session_id: int,