Do not index post's uid field as mysql does not support it

boards/migrations/0056_auto_20170123_1620.py

@@ -0,0 +1,24 b''
+# -*- coding: utf-8 -*-
+# Generated by Django 1.10.5 on 2017-01-23 14:20
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('boards', '0055_auto_20161229_1132'),
+    ]
+
+    operations = [
+        migrations.AlterModelOptions(
+            name='attachment',
+            options={'ordering': ('id',)},
+        ),
+        migrations.AlterField(
+            model_name='post',
+            name='uid',
+            field=models.TextField(),
+        ),
+    ]

boards/models/post/__init__.py

@@ -90,7 +90,7 b' class Post(models.Model, Viewable):'
     thread = models.ForeignKey('Thread', db_index=True, related_name='replies')
 
     url = models.TextField()
-    uid = models.TextField(db_index=True)
+    uid = models.TextField()
 
     # Global ID with author key. If the message was downloaded from another
     # server, this indicates the server.