N+1 Query Detection

Identify and fix N+1 query anti-patterns in Ecto/Phoenix applications.

Iron Laws - Never Violate These

1. Never access associations without preload - Always preload before Enum.map
2. No Repo calls inside loops - Restructure to batch queries
3. Preload at context boundary - Load associations in context, not controllers/views
4. Use joins for filtering - Use join + preload when filtering by association

Detection Patterns

Pattern 1: Enum.map with Repo

# BAD: N+1 queries
users
|> Enum.map(fn user -> Repo.get(Order, user.order_id) end)