python.sqlalchemy.lazy_loading

Performance High

Detects SQLAlchemy queries with lazy loading causing N+1 issues.

Why It Matters

Lazy loading problems:

• N+1 queries — One query per related object
• Slow endpoints — Database round trips
• Database overload — Excessive query count

Example

# ❌ Before (lazy loading causes N+1)
users = session.query(User).all()
for user in users:
    print(user.orders)  # Triggers a query per user!

# ✅ After (eager loading)
from sqlalchemy.orm import joinedload, selectinload

# For one-to-many
users = session.query(User).options(
    selectinload(User.orders)
).all()

# For many-to-one
orders = session.query(Order).options(
    joinedload(Order.user)
).all()

for user in users:
    print(user.orders)  # No additional queries!

What Unfault Detects

• Relationship access in loops
• Missing joinedload/selectinload
• lazy=‘dynamic’ without filtering

Related Rules

• python.n_plus_one_queries