⚡ Bolt: [performance improvement] fix N+1 query in getUserOrders

.jules/bolt.md

@@ -0,0 +1,3 @@
+## 2024-05-15 - [Database Query Optimization: Resolving N+1 Problems]
+**Learning:** Performing database queries within a loop (`Promise.all` with `map`) leads to an N+1 query problem, increasing latency and database load linearly with the size of the initial result set.
+**Action:** Use Drizzle ORMs `inArray` operator to batch related records into a single query and group them in memory using `reduce`, significantly reducing the number of roundtrips and overall execution time.

lib/actions/orders.ts

@@ -3,7 +3,7 @@
 import { db } from "@/lib/db";
 import { orders, orderItems, products, productVariants, user, bargainSessions } from "@/lib/db/schema";
 import { getServerSession } from "@/lib/auth-server";
-import { eq, desc, sql, and, isNull } from "drizzle-orm";
+import { eq, desc, sql, and, isNull, inArray } from "drizzle-orm";
 import { revalidatePath } from "next/cache";
 import { markCouponUsed } from "./admin";
 
@@ -297,22 +297,30 @@ export async function getUserOrders() {
     .where(eq(orders.userId, session.user.id))
     .orderBy(desc(orders.createdAt));
 
-  // Fetch items for each order
-  const ordersWithItems = await Promise.all(
-    userOrders.map(async (order) => {
-      const items = await db
-        .select()
-        .from(orderItems)
-        .where(eq(orderItems.orderId, order.id));
+  if (userOrders.length === 0) {
+    return [];
+  }
 
-      return {
-        ...order,
-        items,
-      };
-    })
-  );
+  // Optimize N+1 query: Fetch all items for all orders in a single query
+  const orderIds = userOrders.map(order => order.id);
+  const allOrderItems = await db
+    .select()
+    .from(orderItems)
+    .where(inArray(orderItems.orderId, orderIds));
 
-  return ordersWithItems;
+  // Group items by orderId
+  const itemsByOrderId = allOrderItems.reduce((acc, item) => {
+    if (!acc[item.orderId]) {
+      acc[item.orderId] = [];
+    }
+    acc[item.orderId].push(item);
+    return acc;
+  }, {} as Record<string, typeof allOrderItems>);
+
+  return userOrders.map(order => ({
+    ...order,
+    items: itemsByOrderId[order.id] || [],
+  }));
 }
 
 // ============================================