#23576: ORM delete strategy can lead to race conditions inside a transaction
-------------------------------------+-------------------------------------
Reporter: jdufresne | Owner: nobody
Type: Uncategorized | Status: new
Component: Database layer | Version: 1.7
(models, ORM) | Resolution:
Severity: Normal | Triage Stage:
Keywords: | Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by jdufresne):
* needs_better_patch: => 0
* needs_tests: => 0
* needs_docs: => 0
Comment:
I have created a minimal test case:
https://github.com/jdufresne/djtest-23576 I'd be happy to answer any
questions about the test case if anything requires explanation. The
waiting on `stdin` is to simulate a view with a long running process
inside a transaction.
To run the test, run `$ python test.py` from the project root directory.
(As it is a race condition it may take more than one try.)
The test runs in a management command instead of a HTTP view in order to
easily trigger the race using multiple processes, but the principle is the
same. Imagine the command is the view and each process is an HTTP request.
Upon running the test and triggering the error I get the following
traceback:
{{{
Traceback (most recent call last):
File "manage.py", line 10, in <module>
execute_from_command_line(sys.argv)
File "/home/jon/djtest/venv/lib/python2.7/site-
packages/django/core/management/__init__.py", line 385, in
execute_from_command_line
utility.execute()
File "/home/jon/djtest/venv/lib/python2.7/site-
packages/django/core/management/__init__.py", line 377, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/home/jon/djtest/venv/lib/python2.7/site-
packages/django/core/management/base.py", line 288, in run_from_argv
self.execute(*args, **options.__dict__)
File "/home/jon/djtest/venv/lib/python2.7/site-
packages/django/core/management/base.py", line 338, in execute
output = self.handle(*args, **options)
File "/home/jon/djtest/venv/lib/python2.7/site-
packages/django/core/management/base.py", line 533, in handle
return self.handle_noargs(**options)
File "/home/jon/djtest/myproj/myapp/management/commands/mytest.py", line
13, in handle_noargs
C(a=A.objects.get(name='foo'), b=B.objects.get(name='bar'))
File "/home/jon/djtest/venv/lib/python2.7/site-
packages/django/db/models/manager.py", line 92, in manager_method
return getattr(self.get_queryset(), name)(*args, **kwargs)
File "/home/jon/djtest/venv/lib/python2.7/site-
packages/django/db/models/query.py", line 409, in bulk_create
self._batched_insert(objs_without_pk, fields, batch_size)
File "/home/jon/djtest/venv/lib/python2.7/site-
packages/django/db/models/query.py", line 938, in _batched_insert
using=self.db)
File "/home/jon/djtest/venv/lib/python2.7/site-
packages/django/db/models/manager.py", line 92, in manager_method
return getattr(self.get_queryset(), name)(*args, **kwargs)
File "/home/jon/djtest/venv/lib/python2.7/site-
packages/django/db/models/query.py", line 921, in _insert
return query.get_compiler(using=using).execute_sql(return_id)
File "/home/jon/djtest/venv/lib/python2.7/site-
packages/django/db/models/sql/compiler.py", line 920, in execute_sql
cursor.execute(sql, params)
File "/home/jon/djtest/venv/lib/python2.7/site-
packages/django/db/backends/utils.py", line 81, in execute
return super(CursorDebugWrapper, self).execute(sql, params)
File "/home/jon/djtest/venv/lib/python2.7/site-
packages/django/db/backends/utils.py", line 65, in execute
return self.cursor.execute(sql, params)
File "/home/jon/djtest/venv/lib/python2.7/site-
packages/django/db/utils.py", line 94, in __exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
File "/home/jon/djtest/venv/lib/python2.7/site-
packages/django/db/backends/utils.py", line 65, in execute
return self.cursor.execute(sql, params)
File "/home/jon/djtest/venv/lib/python2.7/site-
packages/django/db/backends/mysql/base.py", line 128, in execute
return self.cursor.execute(query, args)
File "/home/jon/djtest/venv/lib/python2.7/site-
packages/MySQLdb/cursors.py", line 205, in execute
self.errorhandler(self, exc, value)
File "/home/jon/djtest/venv/lib/python2.7/site-
packages/MySQLdb/connections.py", line 36, in defaulterrorhandler
raise errorclass, errorvalue
django.db.utils.IntegrityError: (1062, "Duplicate entry '1-1' for key
'a_id'")
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/23576#comment:1>
Django <https://code.djangoproject.com/>
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