Eliminate N+1 Database Queries

// ❌ 1 query to get users + N queries to get posts
export async function getUsersWithPosts() {
  const users = await prisma.user.findMany()
 
  const usersWithPosts = await Promise.all(
    users.map(async (user) => {
      const posts = await prisma.post.findMany({
        where: { authorId: user.id },
      })
      return { ...user, posts }
    })
  )
 
  return usersWithPosts
}
// 100 users = 101 database queries 💀

// ✅ Single query with eager loading
export async function getUsersWithPosts() {
  return prisma.user.findMany({
    include: {
      posts: true,
    },
  })
}
// 100 users = 1-2 database queries ✅

// ✅ Two queries instead of N+1
export async function getUsersWithPosts() {
  const users = await prisma.user.findMany()
  const userIds = users.map((u) => u.id)
 
  const posts = await prisma.post.findMany({
    where: { authorId: { in: userIds } },
  })
 
  // Group posts by author in memory
  const postsByAuthor = new Map<string, Post[]>()
  for (const post of posts) {
    const existing = postsByAuthor.get(post.authorId) ?? []
    existing.push(post)
    postsByAuthor.set(post.authorId, existing)
  }
 
  return users.map((user) => ({
    ...user,
    posts: postsByAuthor.get(user.id) ?? [],
  }))
}
// 100 users = 2 database queries ✅

// ❌ Each UserCard triggers its own query
async function UserList() {
  const users = await prisma.user.findMany()
  return users.map((user) => <UserCard key={user.id} userId={user.id} />)
}
 
async function UserCard({ userId }: { userId: string }) {
  // This runs once per card = N queries
  const profile = await prisma.profile.findUnique({
    where: { userId },
  })
  return <div>{profile?.bio}</div>
}
 
// ✅ Fix: fetch all data at the parent level
async function UserList() {
  const users = await prisma.user.findMany({
    include: { profile: true },
  })
  return users.map((user) => <UserCard key={user.id} user={user} />)
}

# Find queries inside .map() or .forEach() — likely N+1
grep -rn "\.map(async" src/ --include="*.ts" --include="*.tsx" -A 3 | grep -E "prisma\.|supabase\.|db\."
# Find queries inside loop bodies
grep -rn "for.*of\|forEach" src/ --include="*.ts" --include="*.tsx" -A 5 | grep -E "await.*\.(find|get|fetch|query)"