optimize homepage queries

doab_check/migrations/0005_alter_check_return_code.py

@@ -0,0 +1,18 @@
+# Generated by Django 4.1.7 on 2023-09-06 16:06
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('doab_check', '0004_auto_20230427_1818'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='check',
+            name='return_code',
+            field=models.IntegerField(db_index=True),
+        ),
+    ]

doab_check/models.py

@@ -78,7 +78,7 @@ class Check(models.Model):
     ''' The results of a link check '''
     created = models.DateTimeField(auto_now_add=True)
     link = models.ForeignKey("Link", related_name='checks', on_delete=models.CASCADE)
-    return_code = models.IntegerField()
+    return_code = models.IntegerField(db_index=True)
     content_type = models.CharField(max_length=255, null=True)
     location = models.ForeignKey("Link", related_name='redirects_from', null=True,
                                  on_delete=models.SET_NULL)

doab_check/views.py

@@ -14,15 +14,15 @@ class HomepageView(generic.TemplateView):
     template_name = 'index.html'
 
     def get_context_data(self, **kwargs):
-        codes = Link.objects.filter(recent_check__isnull=False).order_by(
-            '-recent_check__return_code').values(
+        active_links = Link.objects.filter(recent_check__isnull=False).only(
+            'recent_check').order_by('-recent_check__return_code').distinct()
+        codes = active_links.values(
             'recent_check__return_code').distinct()
-        num_checked = Link.objects.filter(
-                recent_check__return_code__isnull=False).distinct().count()
+        num_checked = active_links.count()
         for code in codes:
-            code['count'] = Link.objects.filter(
+            code['count'] = active_links.filter(
                 recent_check__return_code=code['recent_check__return_code'],
-            ).distinct().count()
+            ).count()
             code['percent'] = '{:.2%}'.format(code['count'] / num_checked)
         return {'num_checked': num_checked, 'codes': codes}