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# Copyright (c) 2025 Oracle and/or its affiliates.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License, version 2.0, as
# published by the Free Software Foundation.
#
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#
# Without limiting anything contained in the foregoing, this file,
# which is part of MySQL Connector/Python, is also subject to the
# Universal FOSS Exception, version 1.0, a copy of which can be found at
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#
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# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
# See the GNU General Public License, version 2.0, for more details.
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"""Atomic transaction context manager utilities for MySQL Connector/Python.
Provides context manager atomic_transaction() that ensures commit on success
and rollback on error without obscuring the original exception.
"""
from contextlib import contextmanager
from typing import Iterator
from mysql.connector.abstracts import MySQLConnectionAbstract
from mysql.connector.cursor import MySQLCursorAbstract
@contextmanager
def atomic_transaction(
conn: MySQLConnectionAbstract,
) -> Iterator[MySQLCursorAbstract]:
"""
Context manager that wraps a MySQL database cursor and ensures transaction
rollback in case of exception.
NOTE: DDL statements such as CREATE TABLE cause implicit commits. These cannot
be managed by a cursor object. Changes made at or before a DDL statement will
be committed and not rolled back. Callers are responsible for any cleanup of
this type.
This class acts as a robust, PEP 343-compliant context manager for handling
database cursor operations on a MySQL connection. It ensures that all operations
executed within the context block are part of the same transaction, and
automatically calls `connection.rollback()` if an exception occurs, helping
to maintain database integrity. On normal completion (no exception), it simply
closes the cursor after use. Exceptions are always propagated to the caller.
Args:
conn: A MySQLConnectionAbstract instance.
"""
old_autocommit = conn.autocommit
cursor = conn.cursor()
exception_raised = False
try:
if old_autocommit:
conn.autocommit = False
yield cursor # provide cursor to block
conn.commit()
except Exception: # pylint: disable=broad-exception-caught
exception_raised = True
try:
conn.rollback()
except Exception: # pylint: disable=broad-exception-caught
# Don't obscure original exception
pass
# Raise original exception
raise
finally:
conn.autocommit = old_autocommit
try:
cursor.close()
except Exception: # pylint: disable=broad-exception-caught
# don't obscure original exception if exists
if not exception_raised:
raise