Remove the done index.

lms/djangoapps/courseware/migrations/0007_remove_done_index.py

@@ -0,0 +1,20 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.13 on 2018-05-29 15:18
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('courseware', '0006_remove_module_id_index'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='studentmodule',
+            name='done',
+            field=models.CharField(choices=[(b'na', b'NOT_APPLICABLE'), (b'f', b'FINISHED'), (b'i', b'INCOMPLETE')], default=b'na', max_length=8),
+        ),
+    ]

lms/djangoapps/courseware/models.py

@@ -111,7 +111,7 @@ class StudentModule(models.Model):
         ('f', 'FINISHED'),
         ('i', 'INCOMPLETE'),
     )
-    done = models.CharField(max_length=8, choices=DONE_TYPES, default='na', db_index=True)
+    done = models.CharField(max_length=8, choices=DONE_TYPES, default='na')
 
     created = models.DateTimeField(auto_now_add=True, db_index=True)
     modified = models.DateTimeField(auto_now=True, db_index=True)