如何正确实现 Peewee 回滚？

Question

I have a code using TestModel which inherits playhouse.postgres_ext.Model, an instance of PostgreSQL as sql_db , an instance of SMTP as smtp for notification

@sql_db.atomic()
def update_jersey():
    TestModel.update(TestModel.jersey_number=24).where(TestModel.first_name="kobe").execute()
    smtp.sendmail(*args, **kwargs)

I want my TestModel.update() to rollback when smtp.sendmail() fails but currently, the code doesn't rollback the update.

I also tried using the logic below but still, rollback is not working.

with sql_db.manual_commit():
    sql_db.begin()
    try:
        TestModel.update()
        smtp.sendmail()
    except Exception:
        sql_db.rollback()
    else:
        sql_db.commit()

I also tried the sql_db.transaction() as txn but still no luck.

How can I implement the rollback given that the Exception is caused by another function and not related to SQL?

Answer 1

You can see in the tests that the atomic decorator and context-manager will roll-back implicitly if an error occurs in the wrapped-block.

Docs here:

http://docs.peewee-orm.com/en/latest/peewee/database.html#managing-transactions

Here's a minimal example:

db = SqliteDatabase(':memory:')

class R(Model):
    value = IntegerField()
    class Meta:
        database = db

db.create_tables([R])

with db.atomic():
    R.create(value=1)

# Explicit rollback
with db.atomic() as txn:
    R.create(value=2)
    txn.rollback()

# Implicit rollback because of exception.
try:
    with db.atomic():
        R.create(value=3)
        4 / 0
except ZeroDivisionError:
    pass

print([x.value for x in R])
# Prints:
# [1]

RIP Kobe