How to force insert custom value in datetimefield(auto_now_add=True) while object creation in Django?

Question

I have a model Test in service A

class Test(models.Model):
    some_field = models.IntegerField()
    created_at = models.DateTimeField(auto_now_add=True)

I am migrating data from a different service B 's model to this model (using APIs). Exposed an API in service A which reads from POST data sent from the B , and saves the data in this Test model.

Sample data coming from service B

data = {
    'some_field': 5,
    'created_at': '2013-06-26 00:14:27.260524',
}

Now when I save this data in the db using:

obj = Test(
        some_field=request.POST.get('some_field'),
        created_at=request.POST.get('created_at'),
      )
obj.save()

The created_at values of saved object is the current time. Not the created_at coming from the API.

How to bypass this current time saving in this scenario and save the timestamp coming from the API while creating the object?

Answer 1

When you have auto_now_add=True you're forcing your records to have current time as their timestamp in the creation time and Django simply ignores this field in the creation moment if you try to pass a value to it (either on calling Test.objects.create() or calling save method on your object for the first time). I think you can handle this problem by doing two different solutions (there might be other solutions as well):

A- Try to change your field value from auto_now_add=True to default=timezone.now :

from django.utils import timezone


class Test(models.Model):
    some_field = models.IntegerField()
    created_at = models.DateTimeField(default=timezone.now)

And then you can pass a value for your created_time in the creation process.

B- If this is a just one time import (or hitting your database multiple times does not have bad impact on your performance) you can try to update every instance after creation part:

obj = Test(some_field=request.POST.get('some_field'))
obj.save()
obj.created_at = request.POST.get('created_at')
obj.save(update_fields=['created_at'])

Note: Make sure that your request.POST.get('created_at') is a valid datetime format, otherwise Django will raise an exception (It must be in YYYY-MM-DD HH:MM[:ss[.uuuuuu]][TZ] format).