Optimized tag DB queries

boards/models/tag.py

@@ -1,94 +1,70 b''
 from django.template.loader import render_to_string
 from django.db import models
-from django.db.models import Count, Sum
+from django.db.models import Count
 from django.core.urlresolvers import reverse
 
-from boards.models import Thread
 from boards.models.base import Viewable
 
 
 __author__ = 'neko259'
 
 
 class TagManager(models.Manager):
 
     def get_not_empty_tags(self):
         """
         Gets tags that have non-archived threads.
         """
 
-        not_empty_tags = list()
-        tags = self.order_by('-required', 'name')
-        for tag in tags:
-            if tag.get_thread_count() > 0:
-                not_empty_tags.append(tag)
-
-        return not_empty_tags
+        return self.filter(thread__archived=False)\
+            .annotate(num_threads=Count('thread')).filter(num_threads__gt=0)
 
 
 class Tag(models.Model, Viewable):
     """
     A tag is a text node assigned to the thread. The tag serves as a board
     section. There can be multiple tags for each thread
     """
 
     objects = TagManager()
 
     class Meta:
         app_label = 'boards'
         ordering = ('name',)
 
     name = models.CharField(max_length=100, db_index=True)
     required = models.BooleanField(default=False)
 
     def __str__(self):
         return self.name
 
     def is_empty(self) -> bool:
         """
         Checks if the tag has some threads.
         """
 
         return self.get_thread_count() == 0
 
     def get_thread_count(self) -> int:
         return self.get_threads().count()
 
-    def get_post_count(self, archived=False):
-        """
-        Gets posts count for the tag's threads.
-        """
-
-        posts_count = 0
-
-        threads = self.get_threads().filter(archived=archived)
-        if threads.exists():
-            posts_count = threads.annotate(posts_count=Count('replies')) \
-                .aggregate(posts_sum=Sum('posts_count'))['posts_sum']
-
-        if not posts_count:
-            posts_count = 0
-
-        return posts_count
-
     def get_url(self):
         return reverse('tag', kwargs={'tag_name': self.name})
 
     def get_threads(self):
-        return Thread.objects.filter(tags__in=[self]).order_by('-bump_time')
+        return self.thread_set.order_by('-bump_time')
 
     def is_required(self):
         return self.required
 
     def get_view(self):
-        #prefix = '##' if self.is_required() else '#'
         link = '<a class="tag" href="{}">{}</a>'.format(
-                self.get_url(), self.name)
+            self.get_url(), self.name)
         if self.is_required():
             link = '<b>{}</b>'.format(link)
         return link
 
     def get_search_view(self, *args, **kwargs):
         return render_to_string('boards/tag.html', {
-                   'tag': self,
-               })
+            'tag': self,
+        })