Update on a QuerySet with filter of field__in='' causes AttributeError

[anonymous]

Let testfield be models.CharField

>>> TestModel.objects.filter(testfield__in='')
[]
>>> TestModel.objects.filter(testfield__in=())
[]
>>> TestModel.objects.filter(testfield__in=()).delete()

>>> TestModel.objects.filter(testfield__in='non-existent-entry').update(testfield='test')
0
>>> TestModel.objects.filter(testfield__in='').update(testfield='test')

as well as

>>> TestModel.objects.filter(testfield__in=()).update(testfield='test')

causes following trackback:

'NoneType' object has no attribute 'rowcount'
File "C:\Python25\lib\site-packages\django\db\models\query.py" in update
  448.         rows = query.execute_sql(None)
File "C:\Python25\lib\site-packages\django\db\models\sql\subqueries.py" in execute_sql
  120.         rows = cursor.rowcount

[Alex Gaynor]

cleaned up formatting.

[Enrico]

Patch to execute_sql in django/db/models/sql/subqueries.py

[Enrico]

I've created a patch over r9904 to fix this issue.

If someone needs a quick fix without patching django, here's an ugly workaround:

try:
    TestModel.objects.filter(testfield__in=()).update(testfield='test')
except AttributeError, e:
    if not e.message.find('rowcount') > 0:
        raise

[Malcolm Tredinnick]

Which database backend has this problem? It might be caused by a bug in the DB API wrapper, since the rowcount attribute is meant to exist always (per PEP 249). At a minimum, I'd like to comment what bug we're working around (if it's something current), but also we should consider reporting upstream.

[Enrico]

I've got this error with MySQL (mysql Ver 14.12 Distrib 5.0.51a, for debian-linux-gnu (i486) using readline 5.2)

The database gets the update but the exception is raised.

[(none)]

Milestone post-1.0 deleted

[Malcolm Tredinnick]

(In [9926]) Fixed insert/update handling when no database interaction is required.

Fixed #10205 as part of this.

[Jacob]

Milestone 1.1 deleted