Hello community,
I'm using a django version 1.3 beta 1 SVN-15481 and a mysql 5 backend
I have the following field definition in my model:
class Jtem(models.Model):
name=models.CharField(blank=True, null=True, max_length=255)
nachname=models.CharField(max_length=255)
Doing manage.py syncdb results in a table with the following definition:
CREATE TABLE `roman_jtem` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`nachname` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci
Now I insert some values in the table so i can run the following:
mysql> select * from roman_jtem where id=29;
+----+------+----------+
| id | name | nachname |
+----+------+----------+
| 29 | NULL | Klesel |
+----+------+----------+
1 row in set (0.00 sec)
Now I will access the table through django and save an empty string to
the name field:
>>> from test_django.roman.models import Jtem
>>> o=Jtem.objects.get(pk=29)
>>> o.name=''
>>> o.save()
Now the record looks like this:
mysql> select * from roman_jtem where id=29;
+----+------+----------+
| id | name | nachname |
+----+------+----------+
| 29 | | Klesel |
+----+------+----------+
1 row in set (0.00 sec)
This is not what I expected! The empty string should have been
converted into a null value!
This behavior causes problems in other models where I access a legacy
database and where I update the model through a ModelForm. Because all
the null Values in the database are replaced with an empty string for
each Model I upddate.
The whole things behaves correctly (to my likings) with the following
patch to the django sources:
diff --git a/django/db/models/fields/__init__.py
b/django/db/models/fields/__init__.py
index fd0a295..569bba6 100644
--- a/django/db/models/fields/__init__.py
+++ b/django/db/models/fields/__init__.py
@@ -554,6 +554,8 @@ class CharField(Field):
return smart_unicode(value)
def get_prep_value(self, value):
+ if self.null and not value:
+ return None
return self.to_python(value)
def formfield(self, **kwargs):
Bug or feature?
Regards Roman
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