Fixes long loading times on satellite page by adding is_decoded boolean field with index on DemodData.

db/base/migrations/0002_demoddata_is_decoded.py

@@ -0,0 +1,20 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.10 on 2018-03-04 08:50
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('base', '0001_squashed_0009_auto_20180103_1931'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='demoddata',
+            name='is_decoded',
+            field=models.BooleanField(db_index=True, default=False),
+        ),
+    ]

db/base/models.py

@@ -8,7 +8,7 @@ from django.conf import settings
 from django.contrib.auth.models import User
 from django.core.validators import MaxValueValidator, MinValueValidator
 from django.db import models
-from django.db.models.signals import post_save
+from django.db.models.signals import post_save, pre_save
 from django.utils.timezone import now
 
 from db.base.helpers import gridsquare
@@ -37,6 +37,10 @@ def _gen_observer(sender, instance, created, **kwargs):
     post_save.connect(_gen_observer, sender=DemodData)
 
 
+def _set_is_decoded(sender, instance, **kwargs):
+    instance.is_decoded = instance.payload_decoded != ''
+
+
 class TransmitterApprovedManager(models.Manager):
     def get_queryset(self):
         return super(TransmitterApprovedManager, self).get_queryset().filter(approved=True)
@@ -179,6 +183,7 @@ class DemodData(models.Model):
                             default=0)
     lng = models.FloatField(validators=[MaxValueValidator(180), MinValueValidator(-180)],
                             default=0)
+    is_decoded = models.BooleanField(default=False, db_index=True)
     timestamp = models.DateTimeField(null=True)
 
     class Meta:
@@ -199,3 +204,4 @@ class DemodData(models.Model):
 
 
 post_save.connect(_gen_observer, sender=DemodData)
+pre_save.connect(_set_is_decoded, sender=DemodData)

db/base/views.py

@@ -88,9 +88,8 @@ def satellite(request, norad):
     satellite = get_object_or_404(satellite_query, norad_cat_id=norad)
     suggestions = Suggestion.objects.filter(satellite=satellite)
     modes = Mode.objects.all()
-    telemetry_data_empty = DemodData.objects.filter(satellite__norad_cat_id=norad,
-                                                    payload_decoded__exact='').count()
-    telemetry_data_count = satellite.payload_frames_count - telemetry_data_empty
+    telemetry_data_count = DemodData.objects.filter(satellite__norad_cat_id=norad,
+                                                    is_decoded=True).count()
 
     try:
         latest_frame = DemodData.objects.get(satellite=satellite,