MySQL Bugs: #92001: Django MySQL Python Connector returns None when Default In

Bug #92001	Django MySQL Python Connector returns None when Default In
Submitted:	13 Aug 2018 23:09	Modified:	28 Mar 2021 2:56
Reporter:	Ciaran O'Sullivan	Email Updates:
Status:	No Feedback	Impact on me:	None
Category:	Connector / Python	Severity:	S2 (Serious)
Version:	8.0.12	OS:	Any
Assigned to:		CPU Architecture:	Any
Tags:	Django, MySql Connector, python

Description:
Hi,

I was working down through the Django Polls Tutorial and when I hit part 4 I get a persistent error.

TypeError at /polls/1/vote/
unsupported operand type(s) for +=: 'NoneType' and 'int'
Request Method:	POST
Request URL:	http://127.0.0.1:8000/polls/1/vote/
Django Version:	2.1
Exception Type:	TypeError
Exception Value:	
unsupported operand type(s) for +=: 'NoneType' and 'int'
Exception Location:	C:\<path>\polls\views.py in vote, line 40
Python Executable:	C:\<path>\venv\Scripts\python.exe
Python Version:	3.6.5

Whenever I have a column that has Zero for a value it seems to be returning None instead of Zero.

How to repeat:
Django URL: https://docs.djangoproject.com/en/2.1/intro/tutorial04/

We define Some Models

class Question(models.Model):
    question_text = models.CharField(max_length=200)
    pub_date = models.DateTimeField('date published')

    def __str__(self):
        return self.question_text

    def was_published_recently(self):
        return self.pub_date >= timezone.now() - datetime.timedelta(days=1)

class Choice(models.Model):
    question = models.ForeignKey(Question, on_delete=models.CASCADE)
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)

    def __str__(self):
        return self.choice_text

We then create some rows, that have 0 for the votes column in Choice.
Whenever the value of votes is 0 it returns None instead of 0.
If I update the table with SQL it is the same problem. 

Suggested fix:
It is easy to replicate, but rather annoying to troubleshooting when new to Django in general. I was able to workaround the issue, by setting 'use_pure':True in the settings.py of Django.

DATABASES = {
    'default': {
        'ENGINE': 'mysql.connector.django',
        'NAME': '<set>',
        'USER': '<set>',
        'PASSWORD': '<set>',
        'HOST': 'localhost',
        'PORT': '3309',
        'OPTIONS': { 'sql_mode': 'STRICT_TRANS_TABLES', 'use_pure':True },
    }
}

Example of not using 'use_pure':True

Attachment: 2018-08-14 00_16_06-127.0.0.1_8000_polls_1_results_.png (image/png, text), 24.32 KiB.

Example of using 'use_pure':True

Attachment: 2018-08-14 00_17_11-127.0.0.1_8000_polls_1_results_.png (image/png, text), 22.84 KiB.

I just ran into this myself and I can confirm this is still a problem with version 8.0.17. Not surprising I guess since this bug submission seems to be untouched since submitted a year ago...

The bug is still there in version 8.0.18.
Your workaround still helps.

Django dev team found it, too: https://code.djangoproject.com/ticket/30469

Hi,
I've tested with Django 2.1.8 and Connector/Python 8.0.12, 8.0.16 and 8.0.18, but I couldn't reproduce the error.

Can you please provide a full traceback?

Thanks.

Please check version 8.0.23.

No feedback was provided for this bug for over a month, so it is
being suspended automatically. If you are able to provide the
information that was originally requested, please do so and change
the status of the bug back to "Open".