#13906: REPEATABLE READ (as used by default on MySQL) breaks atleast
QuerySet.get_or_create().
-------------------------------------+-------------------------------------
Reporter: | Owner:
sebastian_noack | Status: new
Type: | Component: Database layer
Cleanup/optimization | (models, ORM)
Milestone: 1.4 | Severity: Normal
Version: SVN | Keywords: mysql transaction
Resolution: | isolation
Triage Stage: Accepted | Has patch: 1
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-------------------------------------+-------------------------------------
Changes (by kmtracey):
* ui_ux: => 0
Comment:
The repeatable read default is tripping up one of our tests:
{{{
./runtests.py --settings=testdb.innodb
select_for_update.SelectForUpdateTests.test_block
Creating test database for alias 'default'...
Creating test database for alias 'other'...
F
======================================================================
FAIL: test_block (modeltests.select_for_update.tests.SelectForUpdateTests)
----------------------------------------------------------------------
Traceback (most recent call last):
File "/home/kmtracey/django/hg-django/django/test/testcases.py", line
613, in skip_wrapper
return test_func(*args, **kwargs)
File "/home/kmtracey/django/hg-django/django/test/testcases.py", line
613, in skip_wrapper
return test_func(*args, **kwargs)
File "/home/kmtracey/django/hg-
django/tests/modeltests/select_for_update/tests.py", line 209, in
test_block
self.assertEqual('Fred', p.name)
AssertionError: 'Fred' != u'Reinhardt'
----------------------------------------------------------------------
Ran 1 test in 0.301s
FAILED (failures=1)
Destroying test database for alias 'default'...
Destroying test database for alias 'other'...
}}}
It's failing because the test continues to read the already-read value
even though another transaction has committed a different value. We either
need to fix the test to avoid this behavior or (better) figure out how to
fix this problem more globally. Repeatable read does seem to cause more
problems than anything else, but I'm a little worried about backwards
incompatibility of changing the default behavior under Django. Hmpf.
--
Ticket URL: <https://code.djangoproject.com/ticket/13906#comment:17>
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