From 898578852d684ef9b625a2a0857201e5758fee68 Mon Sep 17 00:00:00 2001
From: Nikolai R Kristiansen <nikolaik@gmail.com>
Date: Thu, 7 Jan 2016 23:39:11 +0100
Subject: [PATCH] select_related to the rescue, such performance!

---
 mdb/forms.py        | 16 +++++++++-------
 mdb/models.py       |  7 +------
 mdbsite/settings.py |  1 +
 mdbsite/wsgi.py     |  7 ++++---
 4 files changed, 15 insertions(+), 16 deletions(-)

diff --git a/mdb/forms.py b/mdb/forms.py
index 51dfd6f..2a0d4d0 100644
--- a/mdb/forms.py
+++ b/mdb/forms.py
@@ -4,13 +4,12 @@ from django.forms import ModelChoiceField
 from mdb.models import Interface, Ip4Address
 
 
-class Ipv4ModelChoiceField(ModelChoiceField):
-    # def __init__(self, *args, **kwargs):
-    #     super(Ipv4ModelChoiceField, self).__init__(*args, **kwargs)
-
+class Ip4ModelChoiceField(ModelChoiceField):
     def label_from_instance(self, obj):
-        # TODO improve those labelZ
-        return obj.__str__()
+        if not hasattr(obj, 'interface'):
+            return obj.address
+
+        return "{} ({})".format(obj.address, obj.interface.host.hostname)
 
 
 class InterfaceForm(forms.ModelForm):
@@ -19,4 +18,7 @@ class InterfaceForm(forms.ModelForm):
     def __init__(self, *args, **kwargs):
         super(InterfaceForm, self).__init__(*args, **kwargs)
 
-        self.fields['ip4address'] = Ipv4ModelChoiceField(queryset=Ip4Address.objects.select_related())
+        # Join Ip4Address with tables interface and host,
+        # before printing the select labels that walk those two relations.
+        queryset = Ip4Address.objects.select_related('interface', 'interface__host')
+        self.fields['ip4address'] = Ip4ModelChoiceField(queryset=queryset)
diff --git a/mdb/models.py b/mdb/models.py
index f83aee9..5e55122 100644
--- a/mdb/models.py
+++ b/mdb/models.py
@@ -472,12 +472,7 @@ class Ip4Address(models.Model):
     ping_avg_rtt = models.FloatField(null=True, blank=True)
 
     def __str__(self):
-        # FIXME: generates 2 SQL queries?
-        if not hasattr(self, 'interface'):
-            return self.address
-
-        # FIXME: Remove this when admin is overridden
-        return "{} ({})".format(self.address, self.interface.host.hostname)
+        return self.address
 
     def assigned_to_host(self):
         return self.interface.host
diff --git a/mdbsite/settings.py b/mdbsite/settings.py
index 1e0549c..bf04d3a 100644
--- a/mdbsite/settings.py
+++ b/mdbsite/settings.py
@@ -76,6 +76,7 @@ INSTALLED_APPS = (
     'django.contrib.admin',
     'rest_framework',
     'rest_framework.authtoken',
+    'django_extensions',
 
     'mdb',
 )
diff --git a/mdbsite/wsgi.py b/mdbsite/wsgi.py
index cbb5e87..ac62e0d 100644
--- a/mdbsite/wsgi.py
+++ b/mdbsite/wsgi.py
@@ -1,5 +1,6 @@
-import os
-os.environ.setdefault("DJANGO_SETTINGS_MODULE", "mdb.settings")
-
 from django.core.wsgi import get_wsgi_application
+import os
+
+os.environ.setdefault("DJANGO_SETTINGS_MODULE", "mdbsite.settings")
+
 application = get_wsgi_application()