typescript.n_plus_one_queries

Performance High

Detects database queries inside loops.

Why It Matters

N+1 queries destroy performance:

• Linear scaling — 100 items = 101 queries
• Database strain — Many small queries vs few large ones
• Latency accumulation — Each query adds network round-trip
• Hidden in code — ORMs make it easy to trigger

Example

// ❌ Before
const users = await User.findAll();
for (const user of users) {
    const orders = await Order.findAll({ where: { userId: user.id } });
    console.log(user.name, orders.length);
}

100 users = 101 queries.

// ✅ After
const users = await User.findAll({
    include: [{ model: Order }]
});
for (const user of users) {
    console.log(user.name, user.orders.length);
}

Now it’s 1-2 queries total.

What Unfault Detects

• Database calls inside loops
• Relationship access in iterations
• Missing eager loading

Auto-Fix

Unfault adds eager loading or suggests query restructuring.

ORM Patterns

// Prisma
const users = await prisma.user.findMany({
    include: { orders: true }
});

// Sequelize
const users = await User.findAll({
    include: [Order]
});

// TypeORM
const users = await userRepository.find({
    relations: ['orders']
});

// Manual batching
const userIds = users.map(u => u.id);
const orders = await Order.findAll({
    where: { userId: { [Op.in]: userIds } }
});
const ordersByUser = groupBy(orders, 'userId');

Related Rules

• python.n_plus_one_queries
• go.gorm.n_plus_one