Updating Django ORM with filter is updating unexpected fields-CodePudding

I have a very simple DjangoRestFramework api_view where i am grabbing an id and filtering a queryset by that id and a start date greater than today.

My Model is pretty simple, it has a patient (FK), is_cancelled (boolean), start (Datetime) and end (Datetime).

The issue is that when i run the below update, it is setting the start date to the date and time that i run this view.

@api_view(['POST'])
def BookingCancelAppointmentsView(request):
    if request.method == 'POST':
        patient_id = request.data
        today = date.today()
        bookings = Booking.objects.filter(patient=patient_id, start__gte=today).update(is_cancelled=True)
    return Response({'message': 'Appointments cancelled'})

so for example, if find an entry that is greater than today for that patient_id, it does update the "is_cancelled" field for the correct record but it is setting the Start datetime from whatever datetime i had in there originally to the date.today() value even though i am only updating the "is_cancelled" field.

Does anyone have any idea why it would touch the "start" field at all and how i might get around this issue?

Software Versions:

Python Version: 3.10.5
Django Version: 3.2.15
Django Rest Framework Version: 3.13.1

CodePudding user response：

Try to check your Booking model. It might be because you set auto_now=True on the start field.

Ex.

class Booking(models.Model):
    is_cancelled = models.BooleanField()
    start = models.DateTimeField(auto_now=True)

If auto_now=True the field will be automatically set to now every time the object is saved

CodePudding user response：

If you just need to set the time fields at the time of object creation. You can pass auto_now_add=True, instead of auto_now=True.
The auto_now will update the field every time the save method is called.

class Booking:
    <...other fields here...>
    start = models.DateTimeField(auto_now_add=True)
    end = models.DateTimeField(auto_now_add=True)

Alternative you can use bulk operations to save data to models. On Bulk operations these fields will not be updated. Though this is not a suggested approach, this is just a hack if you don't want to change your models due to some reasons.