dashboard: improve node list performance

circle/dashboard/templates/dashboard/node-list/column-vm.html

 {% load i18n %} 
 
 <div id="node-list-column-vm">
-  <a class="real-link" href="{% url "dashboard.views.node-detail" pk=record.pk %}#virtualmachines">{{ record.instance_set.count }}</a>
+  <a class="real-link" href="{% url "dashboard.views.node-detail" pk=record.pk %}#virtualmachines">{{ value }}</a>
 </div>

circle/dashboard/views.py

@@ -14,6 +14,7 @@ from django.core.exceptions import (
 )
 from django.core import signing
 from django.core.urlresolvers import reverse, reverse_lazy
+from django.db.models import Count
 from django.http import HttpResponse, HttpResponseRedirect, Http404
 from django.shortcuts import redirect, render, get_object_or_404
 from django.views.decorators.http import require_GET
@@ -921,10 +922,13 @@ class VmList(LoginRequiredMixin, SingleTableView):
 
 class NodeList(LoginRequiredMixin, SuperuserRequiredMixin, SingleTableView):
     template_name = "dashboard/node-list.html"
-    model = Node
     table_class = NodeListTable
     table_pagination = False
 
+    def get_queryset(self):
+        return Node.objects.annotate(
+            number_of_VMs=Count('instance_set')).select_related('host')
+
 
 class GroupList(LoginRequiredMixin, SuperuserRequiredMixin, SingleTableView):
     template_name = "dashboard/group-list.html"

circle/vm/models/node.py

@@ -305,7 +305,8 @@ class Node(TimeStampedModel):
 
     @classmethod
     def get_state_count(cls, online, enabled):
-        return len([1 for i in cls.objects.filter(enabled=enabled).all()
+        return len([1 for i in
+                    cls.objects.filter(enabled=enabled).select_related('host')
                     if i.online == online])
 
     @permalink