Opened 3 years ago

Closed 3 years ago

#34523 closed Bug (fixed)

Model.objects.update_or_create method sometimes raises TransactionManagementError

Reported by: gatello-s Owned by: Mariusz Felisiak
Component: Database layer (models, ORM) Version: 4.2
Severity: Normal Keywords: update_or_create TransactionManagementError
Cc: Anton Plotkin, Francesco Panico Triage Stage: Accepted
Has patch: yes Needs documentation: no
Needs tests: no Patch needs improvement: no
Easy pickings: no UI/UX: no

Description (last modified by Anton Plotkin)

When using with myisam-only database the method update_or_create can occur a TransactionManagementError exception if creating a record was unsuccessful (because of IntegrityError, for example the record with a same primary key was already created by another process).

The problem has started after the upgrading from Django 3.2.16 to 4.1.7

The test below just simulates a parallel insertion of the record with the same PK

Database backend: mariadb server (10.5.19) (default-storage-engine is myisam).

This test works fine with Django 3.2.16 and fails on Django 4.1.7+:

class TransactionManagementErrorTest(TestCase):

    class TestModel(models.Model):
        managed = False
        field = models.IntegerField(null=True)

        class Meta(object):
            db_table = 'test_model_update_or_create'

        class QuerySet(models.QuerySet):
            def create(self, **kwargs):
                super().create(**kwargs)  # simulate parallel insertion
                return super().create(**kwargs)
    
        class TestModelManager(models.Manager.from_queryset(QuerySet)):
            pass

        objects = TestModelManager()

    def exec_sql(self, sql):
        from django.db import connections, router
        db = router.db_for_write(self.TestModel)
        connection = connections[db]
        connection.cursor().execute(sql)

    def setUp(self):
        super().setUp()
        self.exec_sql(
            'CREATE TABLE IF NOT EXISTS `test_model_update_or_create` (`id` integer AUTO_INCREMENT NOT NULL PRIMARY KEY, `field` integer NULL);'
        )

    def tearDown(self):
        self.exec_sql(
            'DROP TABLE IF EXISTS `test_model_update_or_create`;'
        )
        super().tearDown()

    def test_update_or_create(self):
        self.TestModel.objects.update_or_create(id=1, defaults={'field': 2})

Exception: django.db.transaction.TransactionManagementError: An error occurred in the current transaction. You can't execute queries until the end of the 'atomic' block.

Failure stack:

Traceback (most recent call last):
  File "/home/alex/workspace/test_TransactionManagementError/mysite/polls/tests.py", line 47, in test_update_or_create
    self.TestModel.objects.update_or_create(id=1, defaults={'field': 2})
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/models/manager.py", line 87, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/models/query.py", line 949, in update_or_create
    obj, created = self.select_for_update().get_or_create(defaults, **kwargs)
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/models/query.py", line 926, in get_or_create
    return self.get(**kwargs), False
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/models/query.py", line 633, in get
    num = len(clone)
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/models/query.py", line 380, in __len__
    self._fetch_all()
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/models/query.py", line 1881, in _fetch_all
    self._result_cache = list(self._iterable_class(self))
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/models/query.py", line 91, in __iter__
    results = compiler.execute_sql(
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/models/sql/compiler.py", line 1560, in execute_sql
    cursor.execute(sql, params)
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/backends/utils.py", line 67, in execute
    return self._execute_with_wrappers(
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/backends/utils.py", line 80, in _execute_with_wrappers
    return executor(sql, params, many, context)
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/backends/utils.py", line 83, in _execute
    self.db.validate_no_broken_transaction()
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/backends/base/base.py", line 531, in validate_no_broken_transaction
    raise TransactionManagementError(
django.db.transaction.TransactionManagementError: An error occurred in the current transaction. You can't execute queries until the end of the 'atomic' block.

Change History (19)

comment:1 by Mariusz Felisiak, 3 years ago

Resolution: → needsinfo
Status: new → closed

What kind of exception are you getting?

comment:2 by Mariusz Felisiak, 3 years ago

Resolution: needsinfo
Status: closed → new

comment:3 by David Sanders, 3 years ago

I ran the test above (I had to add managed=False to the model) on 3.2.16 and I get the same error as it does on main.

Here's the failure with stack trace:

======================================================================
ERROR: test_update_or_create (ticket_34523.tests.TransactionManagementErrorTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/dsanders/projects/django-sample/django/db/models/query.py", line 581, in get_or_create
    return self.get(**kwargs), False
  File "/Users/dsanders/projects/django-sample/django/db/models/query.py", line 435, in get
    raise self.model.DoesNotExist(
ticket_34523.tests.TransactionManagementErrorTest.TestModel.DoesNotExist: TestModel matching query does not exist.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/dsanders/projects/django-sample/django/db/backends/utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)
  File "/Users/dsanders/projects/django-sample/django/db/backends/mysql/base.py", line 73, in execute
    return self.cursor.execute(query, args)
  File "/Users/dsanders/projects/django-sample/.direnv/python-3.10.8/lib/python3.10/site-packages/MySQLdb/cursors.py", line 206, in execute
    res = self._query(query)
  File "/Users/dsanders/projects/django-sample/.direnv/python-3.10.8/lib/python3.10/site-packages/MySQLdb/cursors.py", line 319, in _query
    db.query(q)
  File "/Users/dsanders/projects/django-sample/.direnv/python-3.10.8/lib/python3.10/site-packages/MySQLdb/connections.py", line 255, in query
    _mysql.connection.query(self, query)
MySQLdb.IntegrityError: (1062, "Duplicate entry '1' for key 'test_model_update_or_create.PRIMARY'")

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/Users/dsanders/projects/django-sample/ticket_34523/tests.py", line 44, in test_update_or_create
    self.TestModel.objects.update_or_create(id=1, defaults={"field": 2})
  File "/Users/dsanders/projects/django-sample/django/db/models/manager.py", line 85, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/Users/dsanders/projects/django-sample/django/db/models/query.py", line 608, in update_or_create
    obj, created = self.select_for_update().get_or_create(defaults, **kwargs)
  File "/Users/dsanders/projects/django-sample/django/db/models/query.py", line 588, in get_or_create
    return self.create(**params), True
  File "/Users/dsanders/projects/django-sample/ticket_34523/tests.py", line 16, in create
    return super().create(**kwargs)
  File "/Users/dsanders/projects/django-sample/django/db/models/query.py", line 453, in create
    obj.save(force_insert=True, using=self.db)
  File "/Users/dsanders/projects/django-sample/django/db/models/base.py", line 739, in save
    self.save_base(using=using, force_insert=force_insert,
  File "/Users/dsanders/projects/django-sample/django/db/models/base.py", line 776, in save_base
    updated = self._save_table(
  File "/Users/dsanders/projects/django-sample/django/db/models/base.py", line 881, in _save_table
    results = self._do_insert(cls._base_manager, using, fields, returning_fields, raw)
  File "/Users/dsanders/projects/django-sample/django/db/models/base.py", line 919, in _do_insert
    return manager._insert(
  File "/Users/dsanders/projects/django-sample/django/db/models/manager.py", line 85, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/Users/dsanders/projects/django-sample/django/db/models/query.py", line 1270, in _insert
    return query.get_compiler(using=using).execute_sql(returning_fields)
  File "/Users/dsanders/projects/django-sample/django/db/models/sql/compiler.py", line 1416, in execute_sql
    cursor.execute(sql, params)
  File "/Users/dsanders/projects/django-sample/django/db/backends/utils.py", line 66, in execute
    return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
  File "/Users/dsanders/projects/django-sample/django/db/backends/utils.py", line 75, in _execute_with_wrappers
    return executor(sql, params, many, context)
  File "/Users/dsanders/projects/django-sample/django/db/backends/utils.py", line 79, in _execute
    with self.db.wrap_database_errors:
  File "/Users/dsanders/projects/django-sample/django/db/utils.py", line 90, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File "/Users/dsanders/projects/django-sample/django/db/backends/utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)
  File "/Users/dsanders/projects/django-sample/django/db/backends/mysql/base.py", line 73, in execute
    return self.cursor.execute(query, args)
  File "/Users/dsanders/projects/django-sample/.direnv/python-3.10.8/lib/python3.10/site-packages/MySQLdb/cursors.py", line 206, in execute
    res = self._query(query)
  File "/Users/dsanders/projects/django-sample/.direnv/python-3.10.8/lib/python3.10/site-packages/MySQLdb/cursors.py", line 319, in _query
    db.query(q)
  File "/Users/dsanders/projects/django-sample/.direnv/python-3.10.8/lib/python3.10/site-packages/MySQLdb/connections.py", line 255, in query
    _mysql.connection.query(self, query)
django.db.utils.IntegrityError: (1062, "Duplicate entry '1' for key 'test_model_update_or_create.PRIMARY'")

comment:4 by David Sanders, 3 years ago

Last edited 3 years ago by David Sanders (previous) (diff)

comment:5 by Natalia Bidart, 3 years ago

Besides knowing what exception the reporter is getting, I would like to understand what is the desired outcome, considering that the test is setting the same id for both insertions. I would expect an IntegrityError as shown by David.

comment:6 by Mariusz Felisiak, 3 years ago

Resolution: → needsinfo
Status: new → closed

I'd be surprise at any change in the behavior here. Also, MyISAM storage engine doesn't support transactions, etc. I don't think you've explained the issue in enough detail to confirm a bug in Django. Please reopen the ticket if you can debug your issue and provide details about why and where Django is at fault.

comment:7 by gatello-s, 3 years ago

code from db/models/query.py

return self.create(**params), True

# test generate IntegrityError, this ok

return self.get(**kwargs), False

# this must work fine, but raise django.db.transaction.TransactionManagementError

    def get_or_create(self, defaults=None, **kwargs):
        """
        Look up an object with the given kwargs, creating one if necessary.
        Return a tuple of (object, created), where created is a boolean
        specifying whether an object was created.
        """
        # The get() needs to be targeted at the write database in order
        # to avoid potential transaction consistency problems.
        self._for_write = True
        try:
            return self.get(**kwargs), False
        except self.model.DoesNotExist:
            params = self._extract_model_params(defaults, **kwargs)
            # Try to create an object using passed params.
            try:
                with transaction.atomic(using=self.db):
                    params = dict(resolve_callables(params))
                    return self.create(**params), True  # test generate IntegrityError, this ok
            except IntegrityError:
                try:
                    return self.get(**kwargs), False  # this must work fine, but raise django.db.transaction.TransactionManagementError
                except self.model.DoesNotExist:
                    pass
                raise

ERROR: test_update_or_create (polls.tests.TransactionManagementErrorTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/models/query.py", line 916, in get_or_create
    return self.get(**kwargs), False
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/models/query.py", line 637, in get
    raise self.model.DoesNotExist(
polls.tests.TransactionManagementErrorTest.TestModel.DoesNotExist: TestModel matching query does not exist.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/backends/utils.py", line 89, in _execute
    return self.cursor.execute(sql, params)
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/backends/mysql/base.py", line 75, in execute
    return self.cursor.execute(query, args)
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/MySQLdb/cursors.py", line 206, in execute
    res = self._query(query)
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/MySQLdb/cursors.py", line 320, in _query
    self._do_get_result(db)
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/MySQLdb/cursors.py", line 145, in _do_get_result
    self._result = result = self._get_result()
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/MySQLdb/cursors.py", line 352, in _get_result
    return self._get_db().store_result()
MySQLdb.IntegrityError: (1062, "Duplicate entry '1' for key 'PRIMARY'")

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/models/query.py", line 923, in get_or_create
    return self.create(**params), True
  File "/home/alex/workspace/test_TransactionManagementError/mysite/polls/tests.py", line 19, in create
    return super().create(**kwargs)
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/models/query.py", line 658, in create
    obj.save(force_insert=True, using=self.db)
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/models/base.py", line 814, in save
    self.save_base(
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/models/base.py", line 877, in save_base
    updated = self._save_table(
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/models/base.py", line 1020, in _save_table
    results = self._do_insert(
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/models/base.py", line 1061, in _do_insert
    return manager._insert(
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/models/manager.py", line 87, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/models/query.py", line 1805, in _insert
    return query.get_compiler(using=using).execute_sql(returning_fields)
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/models/sql/compiler.py", line 1820, in execute_sql
    cursor.execute(sql, params)
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/backends/utils.py", line 67, in execute
    return self._execute_with_wrappers(
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/backends/utils.py", line 80, in _execute_with_wrappers
    return executor(sql, params, many, context)
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/backends/utils.py", line 89, in _execute
    return self.cursor.execute(sql, params)
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/utils.py", line 91, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/backends/utils.py", line 89, in _execute
    return self.cursor.execute(sql, params)
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/backends/mysql/base.py", line 75, in execute
    return self.cursor.execute(query, args)
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/MySQLdb/cursors.py", line 206, in execute
    res = self._query(query)
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/MySQLdb/cursors.py", line 320, in _query
    self._do_get_result(db)
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/MySQLdb/cursors.py", line 145, in _do_get_result
    self._result = result = self._get_result()
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/MySQLdb/cursors.py", line 352, in _get_result
    return self._get_db().store_result()
django.db.utils.IntegrityError: (1062, "Duplicate entry '1' for key 'PRIMARY'")

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/home/alex/workspace/test_TransactionManagementError/mysite/polls/tests.py", line 47, in test_update_or_create
    self.TestModel.objects.update_or_create(id=1, defaults={'field': 2})
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/models/manager.py", line 87, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/models/query.py", line 949, in update_or_create
    obj, created = self.select_for_update().get_or_create(defaults, **kwargs)
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/models/query.py", line 926, in get_or_create
    return self.get(**kwargs), False
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/models/query.py", line 633, in get
    num = len(clone)
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/models/query.py", line 380, in __len__
    self._fetch_all()
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/models/query.py", line 1881, in _fetch_all
    self._result_cache = list(self._iterable_class(self))
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/models/query.py", line 91, in __iter__
    results = compiler.execute_sql(
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/models/sql/compiler.py", line 1560, in execute_sql
    cursor.execute(sql, params)
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/backends/utils.py", line 67, in execute
    return self._execute_with_wrappers(
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/backends/utils.py", line 80, in _execute_with_wrappers
    return executor(sql, params, many, context)
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/backends/utils.py", line 83, in _execute
    self.db.validate_no_broken_transaction()
  File "/home/alex/workspace/test_TransactionManagementError/.venv/lib/python3.9/site-packages/django/db/backends/base/base.py", line 531, in validate_no_broken_transaction
    raise TransactionManagementError(
django.db.transaction.TransactionManagementError: An error occurred in the current transaction. You can't execute queries until the end of the 'atomic' block.

comment:8 by Simon Charette, 3 years ago

Backends that don't support transactions is not a particularly well tested area of the code base. Do we even run the full test suite against MyISAM?

I'm curious as to whether you run into the same issue by making your TransactionManagementErrorTest testcase extend TransationTestCase instead of TestCase. I would expect transaction.atomic to be a noop when the backend doesn't support transactions so I wouldn't be surprised if there was an issue with nested atomic blocks on such backends as they also don't support savepoints by definition (Remember that TestCase wraps each tests in an outer atomic block).

I don't see why a TransactionManagementError is raised in the first place when atomic is meant to be a noop as there are no transactions to manage.

Last edited 3 years ago by Simon Charette (previous) (diff)

comment:9 by David Sanders, 3 years ago

Ok so I think I get what OP is reporting here, but when I run the above test on latest main, it works fine.

  • The above test creates an InnoDB table; this causes the test with the duplicate create() calls in the manager to abort the transaction because we can't have 2 rows with pk=1
  • After editing the test to create a MyISAM the test starts passing - I see no issue.

I'd ask if OP can please make sure the test is run against latest main.

comment:10 by Mariusz Felisiak, 3 years ago

Backends that don't support transactions is not a particularly well tested area of the code base. Do we even run the full test suite against MyISAM?

I'm doing this from time to time (e.g. 73766c118781a7f7052bf0a5fbee38b944964e31, 8e89dfe1c24540d33b577377af633694ff57f505, or 331a460f8f2e4f447b68fba491464b68c9b21fd1.)

comment:11 by Anton Plotkin, 3 years ago

Cc: Anton Plotkin added
Description: modified (diff)
Resolution: needsinfo
Status: closed → new
Summary: update_or_create not work in parallel insertion → Model.objects.update_or_create method sometimes raises TransactionManagementError

comment:12 by Mariusz Felisiak, 3 years ago

Bisected to the 331a460f8f2e4f447b68fba491464b68c9b21fd1, however the MyISAM storage engine doesn't support transactions so I'm not sure how it worked before.

comment:13 by Simon Charette, 3 years ago

The changes in 331a460f8f2e4f447b68fba491464b68c9b21fd1 are semantically correct but they had the side effect of making BaseDatabaseWrapper._savepoint_allowed return False and thus savepoint() creation always return None. Remember that MySQL does support transactions and will happily create valid savepoints that can be rolled back and discarded independently of the default storage engine used.

Since update_or_create uses nested atomic to handle possible integrity errors it was previously taking the savepoints created by MySQL as way to mark back the connection as usable. Now that savepoints are not returned anymore it assumes the outer atomic block is tainted as well and raise TransactionManagementError.

I'm not sure why Atomic.__enter__ and __exit__ are not simply noops when transactions are determined to not be supported instead of trying to handle all kind of nesting and savepoint combinations.

  • django/db/transaction.py 

    diff --git a/django/db/transaction.py b/django/db/transaction.py
index 4150cbcbbe..28229f8f3a 100644
    a b def __init__(self, using, savepoint, durable):  
    181181
    182182    def __enter__(self):
    183183        connection = get_connection(self.using)
     184        if not connection.features.supports_transactions:
     185            return
    184186
    185187        if (
    186188            self.durable
    … … def __enter__(self):  
    223225
    224226    def __exit__(self, exc_type, exc_value, traceback):
    225227        connection = get_connection(self.using)
     228        if not connection.features.supports_transactions:
     229            return
    226230
    227231        if connection.in_atomic_block:
    228232            connection.atomic_blocks.pop()

As for the heuristics to determine if a backend supports transaction the situation is definitely weird on MySQL as supports is on a per-table basis and default_storage_engine is really just a guess at that. In this sense 331a460f8f2e4f447b68fba491464b68c9b21fd1 is backward incompatible as it stopped using savepoints which could have an impact on setups that have mixed storage engines. Not sure if this is a supported setup though.

Last edited 3 years ago by Simon Charette (previous) (diff)

in reply to:  13 comment:14 by Mariusz Felisiak, 3 years ago

Replying to Simon Charette:

As for the heuristics to determine if a backend supports transaction the situation is definitely weird on MySQL as supports is on a per-table basis and default_storage_engine is really just a guess at that. In this sense 331a460f8f2e4f447b68fba491464b68c9b21fd1 is backward incompatible as it stopped using savepoints which could have an impact on setups that have mixed storage engines. Not sure if this is a supported setup though.

Would you recommend reverting 331a460f8f2e4f447b68fba491464b68c9b21fd1? (I fine with that)

comment:15 by Simon Charette, 3 years ago

I think that reverting 331a460f8f2e4f447b68fba491464b68c9b21fd1 is less controversial than making Atomic a noop on databases that don't support transactions as the latter would require a larger discussion.

comment:16 by Mariusz Felisiak, 3 years ago

Owner: changed from nobody to Mariusz Felisiak
Status: new → assigned
Triage Stage: Unreviewed → Accepted

comment:17 by Mariusz Felisiak, 3 years ago

Has patch: set

​PR

comment:18 by Francesco Panico, 3 years ago

Cc: Francesco Panico added

comment:19 by GitHub <noreply@…>, 3 years ago

Resolution: → fixed
Status: assigned → closed

In 83339d21:

Fixed #34523 -- Fixed TransactionManagementError in QuerySet.update_or_create() with MyISAM storage engine.

QuerySet.update_or_create() uses nested atomic to handle possible
integrity errors taking savepoints as way to mark back the connection
as usable. Savepoints are not returned when
uses_savepoints/can_release_savepoints feature flags are set to False.
As a consequence, QuerySet.update_or_create() assumed the outer atomic
block is tainted and raised TransactionManagementError.

This commit partly reverts 331a460f8f2e4f447b68fba491464b68c9b21fd1.

Thanks gatello-s for the report.

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