Missing Transaction For Multi Write (ARCH2065)

Key python.orm.missing-transaction-for-multi-write · Severity warning · Category orm

Two or more dependent writes in the same method that are not wrapped in an explicit transaction/atomic block risk partial commits. Make the writes atomic.

Incorrect

def transfer(src, dst, amount):
    src.balance -= amount
    src.save()  # a failure after this loses the money
    dst.balance += amount
    dst.save()

Correct

def transfer(src, dst, amount):
    with transaction.atomic():
        src.balance -= amount
        src.save()
        dst.balance += amount
        dst.save()

Fix

Wrap dependent multi-write operations in transaction.atomic() so they commit all-or-nothing.