duplicate Key violation in Django insert doing after Django update - django

Question

first i update my model instance, after that i tried to insert a new data but showing
"IntegrityError('duplicate key value violates unique constraint "RFIDActivation_ActivationId_key"\nDETAIL: Key ("ActivationId")=(6de9ed9a) already exists.\n',)"
Models.py
class RFIDActivation(models.Model):
RFIDActivationId = models.AutoField(primary_key=True, db_column='RFIDActivationId')
Device = models.ForeignKey(Device, on_delete=models.CASCADE, db_column='DeviceId')
Employee = models.ForeignKey(Employee, on_delete=models.CASCADE, db_column='EmployeeId')
ActivationId = models.CharField(max_length=10, unique=True, default=uuid4().hex[:8])
ActivationStatus = models.CharField(max_length=1)default=None)
class Meta:
db_table = "RFIDActivation"
my serializer.py
class RFIDActivationSerializer(serializers.ModelSerializer):
class Meta:
model = RFIDActivation
fields = '__all__'
view.py
#api_view(["POST"])
#permission_classes([IsAuthenticated])
def rfid_activation_initial(request):
RFIDActivation.objects.filter(Employee=request.POST.get("Employee")).update(
ActivationStatus='2',
ActivationMessage='Abort'
)
rfid_activation = {
'Employee': request.POST.get("Employee"),
'Device': request.POST.get("Device"),
'ActivationStatus': "0",
'ActivationMessage': "RFID Activation Initiated"
}
rfid_serializer = RFIDActivationSerializer(data=rfid_activation)
if rfid_serializer.is_valid():
rfid_serializer.save()
but rfid_serializer.save() shows exceptionexception
Previous ActivationId is using to saving the new data. ActivationId is unique and auto generated. How can i solve this. Error is showing trying to insert after update query
view.py for working fine code only insertion.
#api_view(["POST"])
#permission_classes([IsAuthenticated])
def rfid_data_add(request):
rfid_activation = {
'Employee': request.POST.get("Employee"),
'Device': request.POST.get("Device"),
'ActivationStatus': "0",
'ActivationMessage': "RFID Activation Initiated"
}
rfid_serializer = RFIDActivationSerializer(data=rfid_activation)
if rfid_serializer.is_valid():
rfid_serializer.save()

Answer 1

In restframework, serializer.save() has different behavior based on creation and update. If you pass instance to serializer, it will update the object, otherwise, it will create a new one
#api_view(['POST', 'PUT'])
def rfid_data(request, pk):
"""
Update or delete a rfid data.
"""
rfid_activation = {
...
}
if request.method == 'POST':
rfid_serializer = RFIDActivationSerializer(data=rfid_activation)
if rfid_serializer.is_valid():
rfid_serializer.save()
return Response(rfid_serializer.data,status=status.HTTP_201_CREATED)
return return Response(rfid_serializer.data, status=status.HTTP_400_BAD_REQUEST)
# PUT is used for object update
elif request.method == 'PUT':
rfid = RFIDActivation.objects.get(pk=pk)
# pass instance to your serializer
# pass partial=True to allow partial updates
rfid_serializer = RFIDActivationSerializer(instance=rfid, data=rfid_activation, partial=True)
if rfid_serializer.is_valid():
rfid_serializer.save()
return Response(rfid_serializer.data)
return Response(rfid_serializer.errors, status=status.HTTP_400_BAD_REQUEST)
UPDATE
default is calculated at import time, in your case, your default value for activation_id is calculated once and never change for subsequent instances.
You have to define a function, thus default callable will be updated each time on object creation, read more here
def activation_id_generator(self):
return uuid4().hex[:8]
# then in your class
class RFIDActivation(models.Model):
...
ActivationId = models.CharField(max_length=10, unique=True, default=activation_id_generator)