Disable `auto_now_add` temporarily in a command

Using Django Getting Started
1

Hello everybody, sorry I don’t know exactly in which forum to ask that question.

Here is a simple model for a user action:

class UserAction(models.Model):
    action = models.CharField(...)
    created_at = models.DateTimeField(auto_now_add=True)

For development purpose, I want to make a command to run periodically that fakes user activity throughout the day. In other words, daily at say 8:00 in the morning, my script will bulk create like thousands of UserAction rows for the day, each with different fake created_at values.

The problem is, auto_now_add doesn’t let me save a date manually. Instead, the value will always be the date of creation of the row. auto_now_add is a requirement that cannot be permanently removed from the model.

How could I sort of disable that behaviour just the time it takes to run that script? Basically what I’d see for my command is something like this:

@transaction.atomic

  1. create UserAction instances
  2. disable auto_now_add
  3. bulk create UserAction rows
  4. enable auto_now_add

Is that doable?

2 
In [3]: r = ReportedTime.objects.all().first()

In [4]: r.ts
Out[4]: datetime.datetime(2023, 10, 5, 12, 47, 55, 425039, tzinfo=datetime.timezone.utc)

In [5]: r.ts = now()

In [6]: r.save()

In [7]: r.refresh_from_db()

In [8]: r.ts
Out[8]: datetime.datetime(2024, 10, 21, 14, 42, 13, 431365, tzinfo=datetime.timezone.utc)

Looks to me like you can edit them just fine. What is the problem you’re having?

3

I’m having the behaviour as described here in the docs:

Maybe I can still overwrite the field after creation of the row, but it seems not at creation of the row, or at least not using bulk_create.

# Create
>>> unique_actions = [UserAction(created_at="2010-01-01", action="unique action") for x in range(10)]
>>> UserAction.objects.bulk_create(unique_actions)

# Get
>>> unique_actions = UserAction.objects.filter(action="unique action").values_list("created_at__date", flat=True)
>>> pprint(list(unique_actions))
[datetime.date(2024, 10, 21),
 datetime.date(2024, 10, 21),
 datetime.date(2024, 10, 21),
 datetime.date(2024, 10, 21),
 datetime.date(2024, 10, 21),
 datetime.date(2024, 10, 21),
 datetime.date(2024, 10, 21),
 datetime.date(2024, 10, 21),
 datetime.date(2024, 10, 21),
 datetime.date(2024, 10, 21)]
4

That is correct, as far as creating the objects using the ORM. You could create those rows with custom values if you created them using raw sql.

5

Hi Ken, as always thanks for super fast reply.

Actually it looks like the answer was super simple. Contrary to my assumption, auto_now_add is not enforced at DB level. So just “disable” it in the model field in the script.

# my_script.py
# Prepare
>>> UserAction.created_at.field.auto_now_add = False

# Create
>>> unique_actions = [UserAction(created_at="2010-01-01", action="unique action") for x in range(10)]
>>> UserAction.objects.bulk_create(unique_actions)

# Get
>>> unique_actions = UserAction.objects.filter(action="unique action").values_list("created_at__date", flat=True)
>>> pprint(list(unique_actions))
 [datetime.date(2010, 1, 1),
 datetime.date(2010, 1, 1),
 datetime.date(2010, 1, 1),
 datetime.date(2010, 1, 1),
 datetime.date(2010, 1, 1),
 datetime.date(2010, 1, 1),
 datetime.date(2010, 1, 1),
 datetime.date(2010, 1, 1),
 datetime.date(2010, 1, 1),
 datetime.date(2010, 1, 1)]

# Exit
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