Temporarily Overriding auto_now_add for Bulk Creation

Based on the Django documentation, there are a few approaches you can take to temporarily override the auto_now_add behavior for your bulk creation script.

Option 1: Modify the Field Attribute Temporarily

You can temporarily modify the field's auto_now_add attribute during your script execution:

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from django.db import transaction

@transaction.atomic
def create_fake_user_actions():
    # Store the original auto_now_add value
    original_auto_now_add = UserAction._meta.get_field('created_at').auto_now_add
    
    try:
        # Disable auto_now_add
        UserAction._meta.get_field('created_at').auto_now_add = False
        
        # Create your fake UserAction instances with custom created_at values
        actions = []
        for i in range(1000):
            # Generate a fake timestamp
            fake_timestamp = some_fake_timestamp_function()
            actions.append(UserAction(
                action="Some action",
                created_at=fake_timestamp
            ))
        
        # Bulk create with custom timestamps
        UserAction.objects.bulk_create(actions)
        
    finally:
        # Restore the original auto_now_add value
        UserAction._meta.get_field('created_at').auto_now_add = original_auto_now_add

Option 2: Use Raw SQL

Since bulk operations don't call model methods or signals, you could use raw SQL to insert the records with custom timestamps:

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from django.db import connection

def create_fake_user_actions_with_sql():
    actions = []
    for i in range(1000):
        fake_timestamp = some_fake_timestamp_function()
        actions.append((f"Action {i}", fake_timestamp))
    
    with connection.cursor() as cursor:
        cursor.executemany(
            "INSERT INTO your_app_useraction (action, created_at) VALUES (%s, %s)",
            actions
        )

Option 3: Create a Custom Manager Method

You could create a custom manager for your model that provides a method for bulk creation with custom timestamps:

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class UserActionManager(models.Manager):
    def bulk_create_with_custom_timestamps(self, objects):
        # Temporarily disable auto_now_add
        original_auto_now_add = self.model._meta.get_field('created_at').auto_now_add
        self.model._meta.get_field('created_at').auto_now_add = False
        
        try:
            return self.bulk_create(objects)
        finally:
            # Restore auto_now_add
            self.model._meta.get_field('created_at').auto_now_add = original_auto_now_add

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

Then use it like:

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actions = [
    UserAction(action="Some action", created_at=some_fake_timestamp_function())
    for i in range(1000)
]
UserAction.objects.bulk_create_with_custom_timestamps(actions)

Important Note

As mentioned in the Django documentation, bulk operations like bulk_create don't call model methods like save() or signals like pre_save and post_save. This means that the auto_now_add behavior is actually implemented in the pre_save method of the DateTimeField, which won't be called during bulk operations.

However, Django's ORM still handles setting default values during bulk creation, which is why we need to temporarily disable the auto_now_add attribute.