I have created a ListView in DRF 3. As database structure is complex I have written a custom query ie raw query to fetch the data. But as the data size is huge, it takes a lot of time to load it. So I need to implement pagination. Below is the code.
class SubnetList(APIView):
def get(self, request, format=None):
subnet_list = get_subnet_details(None)
return Response(subnet_list, status=status.HTTP_200_OK)
def get_subnet_details(subnet_id=None):
if subnet_id:
subnets = Subnet.objects.filter(id=subnet_id).values()
if not subnets:
raise Http404
else:
subnets = Subnet.objects.values()
subnet_list = []
subnet_option_query = ' SELECT ' \
' options_value.id as value_id,' \
' options_value.content,' \
' options_option.id,' \
' options_option.name' \
' FROM subnets_subnetoption' \
' INNER JOIN subnets_subnet ON (subnets_subnetoption.subnet_id = subnets_subnet.id)' \
' INNER JOIN options_value ON (subnets_subnetoption.value_id = options_value.id)' \
' INNER JOIN options_option ON (options_value.option_id = options_option.id)' \
' INNER JOIN options_scope ON (options_option.scope_id = options_scope.id)' \
' WHERE subnets_subnetoption.subnet_id = %s '
try:
for subnet in subnets:
subnet_dictionary = collections.OrderedDict()
subnet_dictionary['subnet_id'] = str(subnet['id'])
subnet_dictionary['name'] = str(subnet['name'])
subnet_dictionary['base_address'] = str(subnet['base_address'])
subnet_dictionary['bcast_address'] = str(subnet['bcast_address'])
subnet_dictionary['bits'] = str(subnet['bits'])
subnet_dictionary['begin'] = str(subnet['base_address'])
subnet_dictionary['end'] = str(subnet['bcast_address'])
subnet_dictionary['parent_id'] = str(subnet['parent_id'])
subnet_dictionary['vlan_common_name'] = str(subnet['vlan_common_name'])
subnet_dictionary['admin'] = str(subnet['admin'])
subnet_dictionary['responsible'] = str(subnet['responsible'])
subnet_dictionary['comments'] = str(subnet['comments'])
super_subnet = 'True' if subnet['is_physical'] else 'False'
subnet_dictionary['is_physical'] = super_subnet
options = SubnetOption.objects.raw(subnet_option_query % (subnet['id']))
physical_attributes = collections.OrderedDict()
range_attributes = collections.OrderedDict()
gatewaydevice_attributes = collections.OrderedDict()
securityzone_attributes = collections.OrderedDict()
for option in options:
if option.name.lower() == 'provider':
subnet_dictionary['provider'] = str(option.value_id)
elif option.name.lower() == 'customer':
subnet_dictionary['customer'] = str(option.value_id)
elif option.name == 'Allocated by RIPE/ARIN/APNIC':
subnet_dictionary['allocated_by'] = str(option.value_id)
if super_subnet == 'True':
if option.name.lower() == 'vlan usage':
physical_attributes['vlan_usage'] = str(option.value_id)
elif option.name.lower() == 'environment':
physical_attributes['environment'] = str(option.value_id)
elif option.name.lower() == 'status':
physical_attributes['status'] = str(option.value_id)
elif option.name.lower() == 'vrf':
physical_attributes['vrf'] = str(option.value_id)
elif option.name.lower() == 'dns on demand status':
physical_attributes['dns_on_demand_status'] = str(option.value_id)
dmz = 'True' if subnet['dmz'] else 'False'
physical_attributes['dmz'] = dmz
except ValueError as e:
print(e)
pass
return subnet_list
Pass in a couple more parameters (you can make them optional if you want) - something like page
and pagesize
. Then use them to limit the query. For MySQL it would be something like LIMIT (pagesize * page),page
. However, the specifics will vary depending on the database engine.
So, use the Django ORM . I can't say for sure without seeing the models, but I am fairly certain you can rewrite the query as a simple Django ORM query:
SubnetOption.objects.filter(subnet=subnet['id'])
and the various INNER JOINs should come through automagically.
Then you can use a range line [page*pagesize:(page+1)*pagesize]
at the end of the query and Django will translate that into a LIMIT or the equivalent for your database engine.
First, create a file named pagination.py in your app. then copy these codes:
class LargeResultsSetPagination(PageNumberPagination):
page_size = 1000
page_size_query_param = 'page_size'
max_page_size = 10000
class StandardResultsSetPagination(PageNumberPagination):
page_size = 100
page_size_query_param = 'page_size'
max_page_size = 1000
After that, you can use from those classes like example below:
class BillingRecordsView(generics.ListAPIView):
queryset = Billing.objects.all()
serializer_class = BillingRecordsSerializer
pagination_class = LargeResultsSetPagination
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