Added indices to the Schedule model

These new indices will allow for more efficient querying of schedules.

openedx/core/djangoapps/schedules/migrations/0002_auto_20170816_1532.py

+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('schedules', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='schedule',
+            name='start',
+            field=models.DateTimeField(help_text='Date this schedule went into effect', db_index=True),
+        ),
+        migrations.AlterField(
+            model_name='schedule',
+            name='upgrade_deadline',
+            field=models.DateTimeField(help_text='Deadline by which the learner must upgrade to a verified seat', null=True, db_index=True, blank=True),
+        ),
+    ]

openedx/core/djangoapps/schedules/models.py

@@ -5,10 +5,17 @@ from django_extensions.db.models import TimeStampedModel
 
 class Schedule(TimeStampedModel):
     enrollment = models.OneToOneField('student.CourseEnrollment', null=False)
-    active = models.BooleanField(default=True, help_text=_('Indicates if this schedule is actively used'))
-    start = models.DateTimeField(help_text=_('Date this schedule went into effect'))
+    active = models.BooleanField(
+        default=True,
+        help_text=_('Indicates if this schedule is actively used')
+    )
+    start = models.DateTimeField(
+        db_index=True,
+        help_text=_('Date this schedule went into effect')
+    )
     upgrade_deadline = models.DateTimeField(
         blank=True,
+        db_index=True,
         null=True,
         help_text=_('Deadline by which the learner must upgrade to a verified seat')
     )