Closes #10197: Add a cached counter field for virtual chassis members

netbox/dcim/migrations/0177_virtual_chassis_member_counter.py

@@ -0,0 +1,35 @@
+from django.db import migrations
+from django.db.models import Count
+
+import utilities.fields
+
+
+def populate_virtualchassis_members(apps, schema_editor):
+    VirtualChassis = apps.get_model('dcim', 'VirtualChassis')
+
+    vcs = list(VirtualChassis.objects.annotate(_member_count=Count('members', distinct=True)))
+
+    for vc in vcs:
+        vc.member_count = vc._member_count
+
+    VirtualChassis.objects.bulk_update(vcs, ['member_count'])
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ('dcim', '0176_device_component_counters'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='virtualchassis',
+            name='member_count',
+            field=utilities.fields.CounterCacheField(
+                default=0, to_field='virtual_chassis', to_model='dcim.Device'
+            ),
+        ),
+        migrations.RunPython(
+            code=populate_virtualchassis_members,
+            reverse_code=migrations.RunPython.noop
+        ),
+    ]