1
That is because the moment you apply values to the queryset, it returns a list of dictionary, whereas the admin is expecting a queryset of objects.
I have been in this situation before, so I did something like this:
def changelist_view(self, request, extra_context=None):
response = super().changelist_view(request, extra_context)
try:
# this is the final queryset to be rendered on the page after pagination.
_cl = response.context_data['cl']
qs = _cl.result_list._clone()
# since in my case mysql 5.5 does'nt support subquery with LIMIT
# fetch all the ips on that page
ips = list(set([obj.ip_address for obj in qs]))
result_qs = models.Log.objects.values('ip_address') \
.filter(ip_address__in=ips) \
.annotate(ip_address_count=Count('ip_address'))
result = {_r['ip_address']: _r['ip_address_count'] for _r in result_qs}
setattr(self, '_ip_addr_count', result)
except:
pass
return response
def ip_address_count(self, instance):
# fetch the count from the dict we set above
return self._ip_addr_count.get(instance.ip_address)
Hence you see what I did is, fetch the ips from the final queryset and then using that to query the count. By doing this you will query the database only once per page.
I hope you get the basic underlying idea.Please suit it according to your need.
6
Here is how you can do natively. Django knows how to handle this (see the documentation about the admin and list_display).
class LogAdmin(admin.ModelAdmin):
list_display = (..., "field1", "field2"... "quantity_of_things",)
def get_queryset(self, request):
return (super(LogAdmin, self).get_queryset(request).annotate(quantity_of_things=Count("xxxxxx")))
def quantity_of_things(self, obj):
return obj.quantity_of_things
quantity_of_things.short_description = "Number of xxxxxx"
You annotate the queryset with anything you need (a Count for instance). As you can see, you just have to use the same name 3 times (quantity_of_things in my example)
- in the list_display (Django understands this is a callable),
- in the annotate,
- in the function to be called.
quantity_of_things.short_descriptionis for the column title