Fix performance issue for users with many orders

src/allmende_payment_system/api/admin.py

@@ -4,6 +4,7 @@ from typing import Annotated
 from fastapi import APIRouter, File, Form, HTTPException, Request
 from sqlalchemy import func, select
 from sqlalchemy.exc import IntegrityError
+from sqlalchemy.orm import selectinload
 from starlette import status
 from starlette.responses import RedirectResponse
 
@@ -12,6 +13,7 @@ from allmende_payment_system.api.dependencies import SessionDep, UserDep
 from allmende_payment_system.models import (
     Account,
     Area,
+    Order,
     Permission,
     Product,
     ProductDetails,
@@ -310,7 +312,13 @@ async def get_accounts(
 
     templates = get_jinja_renderer()
 
-    accounts = session.scalars(select(Account)).all()
+    accounts = session.scalars(
+        select(Account).options(
+            selectinload(Account.transactions)
+            .selectinload(Transaction.order)
+            .selectinload(Order.items)
+        )
+    ).all()
     users = session.scalars(select(User)).all()
 
     return templates.TemplateResponse(

src/allmende_payment_system/api/shop.py

@@ -85,8 +85,8 @@ async def add_to_cart(request: Request, session: SessionDep, user: UserDep):
     order_item = OrderItem(
         product=product, quantity=quantity, total_amount=total_amount
     )
-    session.add(order_item)
     cart = user.shopping_cart
+    session.add(order_item)
     cart.items.append(order_item)
 
     session.flush()