Don't store threads list of a tag, cause this data can be got from thread's tags relations

boards/migrations/0003_remove_tag_threads.py

@@ -0,0 +1,18 b''
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import models, migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('boards', '0002_auto_20141118_2234'),
+    ]
+
+    operations = [
+        migrations.RemoveField(
+            model_name='tag',
+            name='threads',
+        ),
+    ]

boards/models/post.py

@@ -268,18 +268,6 b' class Post(models.Model, Viewable):'
         thread.last_edit_time = edit_time
         thread.save(update_fields=['last_edit_time'])
 
-    @transaction.atomic
-    def remove_tag(self, tag):
-        edit_time = timezone.now()
-
-        thread = self.get_thread()
-        thread.remove_tag(tag)
-        self.last_edit_time = edit_time
-        self.save(update_fields=['last_edit_time'])
-
-        thread.last_edit_time = edit_time
-        thread.save(update_fields=['last_edit_time'])
-
     def get_url(self, thread=None):
         """
         Gets full url to the post.

boards/models/tag.py

@@ -36,8 +36,6 b' class Tag(models.Model, Viewable):'
         ordering = ('name',)
 
     name = models.CharField(max_length=100, db_index=True)
-    threads = models.ManyToManyField(Thread, null=True,
-                                     blank=True, related_name='tag+')
 
     def __str__(self):
         return self.name

boards/models/thread.py

@@ -136,7 +136,6 b' class Thread(models.Model):'
         """
 
         self.tags.add(tag)
-        tag.threads.add(self)
 
     def get_opening_post(self, only_id=False):
         """