Optimize migrate to new ip address field type

devapp/migrations/0005_device_ip_address_change.py

@@ -1,11 +1,11 @@
 # -*- coding: utf-8 -*-
-# Generated by Django 1.11 on 2018-06-12 11:24
+# Generated by Django 1.11 on 2018-08-08 17:31
 from __future__ import unicode_literals
-import os
 from json import load
+import os
+from django.core import serializers
 
 from django.db import migrations, models
-from django.core import serializers
 
 
 TMP_FILE = '/tmp/djing_ip_field_devapp_migrate.json'
@@ -13,9 +13,9 @@ TMP_FILE = '/tmp/djing_ip_field_devapp_migrate.json'
 
 def device_backup_info(apps, _):
     Device = apps.get_model('devapp', 'Device')
-    obs = Device.objects.all()
+    obs = Device.objects.exclude(ip_address=None).only('ip_address')
     with open(TMP_FILE, 'w') as f:
-        serializers.serialize('json', obs, stream=f)
+        serializers.serialize('json', obs, stream=f, fields=('ip_address',))
 
 
 def device_restore_info_to_new_scheme(apps, _):
@@ -28,7 +28,6 @@ def device_restore_info_to_new_scheme(apps, _):
 
 
 class Migration(migrations.Migration):
-
     dependencies = [
         ('devapp', '0004_device_extra_data'),
     ]
@@ -38,7 +37,7 @@ class Migration(migrations.Migration):
         migrations.AlterField(
             model_name='device',
             name='ip_address',
-            field=models.GenericIPAddressField(blank=True, null=True, protocol='ipv4', verbose_name='Ip address'),
+            field=models.GenericIPAddressField(blank=True, null=True, verbose_name='Ip address'),
         ),
         migrations.RunPython(device_restore_info_to_new_scheme)
     ]