GraphQL: пример кода

# Schema: the typed contract, introspectable by tooling
type User { id: ID!, name: String!, orders: [Order!]! }
type Order { id: ID!, total: Int!, items: [Item!]! }
type Query { user(id: ID!): User }

// ❌ N+1: this resolver runs once PER user in the list → 100 DB round trips
const resolvers = {
  User: {
    company: (user) => db.company.findById(user.companyId), // fires per user
  },
};

// ✅ DataLoader batches all companyId lookups in one tick into ONE query
const companyLoader = new DataLoader(async (ids) => {
  const rows = await db.company.findMany({ where: { id: { in: ids } } });
  return ids.map((id) => rows.find((r) => r.id === id)); // must return in input order
});
const resolvers = {
  User: { company: (user) => companyLoader.load(user.companyId) }, // batched + cached
};

// Client: fetch exactly what the view needs — no over/under-fetch
const { data } = useQuery(gql`
  query { user(id: 7) { name orders(last: 3) { total } } }
`);