If an exception occurs in a wrapped block, the current transaction/savepoint will be rolled back. Otherwise the statements will be committed at the end of the wrapped block.

Note

While inside a block wrapped by the context manager, you can explicitly rollback or commit at any point by calling Transaction.rollback() or Transaction.commit(). When you do this inside a wrapped block of code, a new transaction will be started automatically.

Note

atomic() can be used as either a context manager or a decorator.

Using atomic as context manager:

db = SqliteDatabase(':memory:')
with db.atomic() as txn:
    # This is the outer-most level, so this block corresponds to
    # a transaction.
    User.create(username='charlie')
    with db.atomic() as nested_txn:
        # This block corresponds to a savepoint.
        User.create(username='huey')
        # This will roll back the above create() query.
        nested_txn.rollback()
    User.create(username='mickey')
# When the block ends, the transaction is committed (assuming no error
# occurs). At that point there will be two users, "charlie" and "mickey".

try:
    with db.atomic():
        user = User.create(username=username)
    return 'Success'
except peewee.IntegrityError:
    return 'Failure: %s is already in use.' % username

Decorator

Using atomic as a decorator:

atomic() provides transparent nesting of transactions. When using , the outer-most call will be wrapped in a transaction, and any nested calls will use savepoints.

with db.atomic() as txn:
    perform_operation()
    with db.atomic() as nested_txn:
        perform_another_operation()

Peewee supports nested transactions through the use of savepoints (for more information, see savepoint()).

Explicit transaction

If you wish to explicitly run code in a transaction, you can use transaction(). Like , transaction() can be used as a context manager or as a decorator.

If an exception occurs in a wrapped block, the transaction will be rolled back. Otherwise the statements will be committed at the end of the wrapped block.

db = SqliteDatabase(':memory:')
with db.transaction() as txn:
    # Delete the user and their associated tweets.

Transactions can be explicitly committed or rolled-back within the wrapped block. When this happens, a new transaction will be started.

If you attempt to nest transactions with peewee using the context manager, only the outer-most transaction will be used. However if an exception occurs in a nested block, this can lead to unpredictable behavior, so it is strongly recommended that you use .

Just as you can explicitly create transactions, you can also explicitly create savepoints using the method. Savepoints must occur within a transaction, but can be nested arbitrarily deep.

with db.transaction() as txn:
    with db.savepoint() as sp:
        User.create(username='mickey')
    with db.savepoint() as sp2:
        User.create(username='zaizee')
        sp2.rollback()  # "zaizee" will not be saved, but "mickey" will be.

Warning

If you manually commit or roll back a savepoint, a new savepoint will not automatically be created. This differs from the behavior of transaction, which will automatically open a new transaction after manual commit/rollback.

Autocommit Mode

By default, Peewee operates in autocommit mode, such that any statements executed outside of a transaction are run in their own transaction. To group multiple statements into a transaction, Peewee provides the context-manager/decorator. This should cover all use-cases, but in the unlikely event you want to temporarily disable Peewee’s transaction management completely, you can use the Database.manual_commit() context-manager/decorator.

Here is how you might emulate the behavior of the context manager:

with db.manual_commit():
    db.begin()  # Have to begin transaction explicitly.
    try:
        user.delete_instance(recursive=True)
    except:
        db.rollback()  # Rollback! An error occurred.
        raise
    else:
        try:
            db.commit()  # Commit changes.
        except:
            db.rollback()