Cache post's threads count, don't load all threads each time

boards/models/post/__init__.py

@@ -2,6 +2,7 b' import logging'
 import re
 import uuid
 
+from boards.utils import cached_result, datetime_to_epoch
 from django.core.exceptions import ObjectDoesNotExist
 from django.core.urlresolvers import reverse
 from django.db import models
@@ -107,11 +108,6 b' class Post(models.Model, Viewable):'
     def __str__(self):
         return 'P#{}/{}'.format(self.id, self.get_title())
 
-    def get_referenced_posts(self):
-        threads = self.get_threads().all()
-        return self.referenced_posts.filter(threads__in=threads)\
-            .order_by('pub_time').distinct().all()
-
     def get_title(self) -> str:
         return self.title
 
@@ -176,6 +172,13 b' class Post(models.Model, Viewable):'
 
         return self.threads
 
+    def _get_cache_key(self):
+        return [datetime_to_epoch(self.last_edit_time)]
+
+    @cached_result(key_method=_get_cache_key)
+    def get_thread_count(self):
+        return self.get_threads().count()
+
     def get_view(self, *args, **kwargs) -> str:
         """
         Renders post's HTML view. Some of the post params can be passed over
@@ -312,7 +315,7 b' class Post(models.Model, Viewable):'
         ID.
         """
 
-        if self.get_threads().count() > 1:
+        if self.get_thread_count() > 1:
             return '{}/{}'.format(self.get_thread().get_opening_post_id(), self.id)
         else:
             return str(self.id)

boards/models/thread.py

@@ -181,7 +181,7 b' class Thread(models.Model):'
         """
 
         query = self.multi_replies.order_by('pub_time').prefetch_related(
-            'images', 'thread', 'threads', 'attachments')
+            'images', 'thread', 'attachments')
         if view_fields_only:
             query = query.defer('poster_ip')
         return query