Merge pull request #4061 from samar-hassan/samar/optimise-user-order-count

[FEAT] Optimize order count calculation in user listing page

sandbox/fixtures/orders.json

     },
     "model": "order.orderdiscount",
     "pk": 1
+},
+{
+    "fields": {
+        "user": 1,
+        "num_product_views": 1,
+        "num_basket_additions": 1,
+        "num_orders": 1,
+        "num_order_lines": 1,
+        "num_order_items": 1,
+        "total_spent": 7.99,
+        "date_last_order": "2014-10-10T13:07:36.499Z"
+    },
+    "model": "analytics.userrecord",
+    "pk": 1
 }
 ]

src/oscar/apps/dashboard/users/tables.py

     active = Column(accessor='is_active')
     staff = Column(accessor='is_staff')
     date_registered = Column(accessor='date_joined')
-    num_orders = Column(accessor='orders__count', orderable=False, verbose_name=_('Number of Orders'))
+    num_orders = Column(accessor='userrecord__num_orders', default=0,
+                        verbose_name=_('Number of Orders'))
     actions = TemplateColumn(
         template_name='oscar/dashboard/users/user_row_actions.html',
         verbose_name=' ')

src/oscar/apps/dashboard/users/views.py

         return kwargs
 
     def get_queryset(self):
-        queryset = self.model.objects.all().order_by('-date_joined')
+        queryset = self.model.objects.select_related('userrecord').order_by('-date_joined')
         return self.apply_search(queryset)
 
     def apply_search(self, queryset):