Speed up tag list generation a bit

boards/models/tag.py

@@ -41,9 +41,9 b' class Tag(models.Model):'
         return self.name
 
     def is_empty(self):
-        return self.get_post_count() == 0
+        return self.get_thread_count() == 0
 
-    def get_post_count(self):
+    def get_thread_count(self):
         return self.threads.count()
 
     def get_popularity(self):
@@ -51,13 +51,9 b' class Tag(models.Model):'
 
         tag_reply_count = 0.0
 
-        for thread in self.threads.all():
-            if thread.archived:
-                modifier = ARCHIVE_POPULARITY_MODIFIER
-            else:
-                modifier = 1
-            tag_reply_count += thread.get_reply_count() * modifier \
-                    / thread.tags.all().count()
+        tag_reply_count += self.get_post_count()
+        tag_reply_count +=\
+            self.get_post_count(archived=True) * ARCHIVE_POPULARITY_MODIFIER
 
         popularity = tag_reply_count / all_post_count
 
@@ -92,3 +88,12 b' class Tag(models.Model):'
         font_value = min(font_value, MAX_TAG_FONT)
 
         return str(font_value)
+
+    def get_post_count(self, archived=False):
+        posts_count = 0
+
+        for thread in self.threads.annotate(Count('replies')).filter(
+                archived=archived):
+            posts_count += thread.replies__count
+
+        return posts_count