Use more efficient way to get last replies

boards/models/thread.py

@@ -1,185 +1,185 b''
 import logging
 
 from django.db.models import Count, Sum
 from django.utils import timezone
 from django.db import models
 
 from boards import settings
 from boards.utils import cached_result
 from boards.models.post import Post
 
 
 __author__ = 'neko259'
 
 
 logger = logging.getLogger(__name__)
 
 
 class ThreadManager(models.Manager):
     def process_oldest_threads(self):
         """
          Preserves maximum thread count. If there are too many threads,
          archive or delete the old ones.
          """
 
         threads = Thread.objects.filter(archived=False).order_by('-bump_time')
         thread_count = threads.count()
 
         if thread_count > settings.MAX_THREAD_COUNT:
             num_threads_to_delete = thread_count - settings.MAX_THREAD_COUNT
             old_threads = threads[thread_count - num_threads_to_delete:]
 
             for thread in old_threads:
                 if settings.ARCHIVE_THREADS:
                     self._archive_thread(thread)
                 else:
                     thread.delete()
 
             logger.info('Processed %d old threads' % num_threads_to_delete)
 
     def _archive_thread(self, thread):
         thread.archived = True
         thread.bumpable = False
         thread.last_edit_time = timezone.now()
         thread.save(update_fields=['archived', 'last_edit_time', 'bumpable'])
 
 
 class Thread(models.Model):
     objects = ThreadManager()
 
     class Meta:
         app_label = 'boards'
 
     tags = models.ManyToManyField('Tag')
     bump_time = models.DateTimeField(db_index=True)
     last_edit_time = models.DateTimeField()
     archived = models.BooleanField(default=False)
     bumpable = models.BooleanField(default=True)
 
     def get_tags(self):
         """
         Gets a sorted tag list.
         """
 
         return self.tags.order_by('name')
 
     def bump(self):
         """
         Bumps (moves to up) thread if possible.
         """
 
         if self.can_bump():
             self.bump_time = timezone.now()
 
             if self.get_reply_count() >= settings.MAX_POSTS_PER_THREAD:
                 self.bumpable = False
 
             logger.info('Bumped thread %d' % self.id)
 
     def get_reply_count(self):
         return self.get_replies().count()
 
     def get_images_count(self):
         return self.get_replies().annotate(images_count=Count(
                 'images')).aggregate(Sum('images_count'))['images_count__sum']
 
     def can_bump(self):
         """
         Checks if the thread can be bumped by replying to it.
         """
 
         return self.bumpable
 
     def get_last_replies(self):
         """
         Gets several last replies, not including opening post
         """
 
         if settings.LAST_REPLIES_COUNT > 0:
             reply_count = self.get_reply_count()
 
             if reply_count > 0:
                 reply_count_to_show = min(settings.LAST_REPLIES_COUNT,
                                           reply_count - 1)
                 replies = self.get_replies()
-                last_replies = replies[reply_count - reply_count_to_show:]
+                last_replies = replies.reverse()[:reply_count_to_show]
 
                 return last_replies
 
     def get_skipped_replies_count(self):
         """
         Gets number of posts between opening post and last replies.
         """
         reply_count = self.get_reply_count()
         last_replies_count = min(settings.LAST_REPLIES_COUNT,
                                  reply_count - 1)
         return reply_count - last_replies_count - 1
 
     def get_replies(self, view_fields_only=False):
         """
         Gets sorted thread posts
         """
 
         query = Post.objects.filter(threads__in=[self])
         query = query.order_by('pub_time').prefetch_related('images', 'thread', 'threads')
         if view_fields_only:
             query = query.defer('poster_user_agent')
         return query.all()
 
     def get_replies_with_images(self, view_fields_only=False):
         """
         Gets replies that have at least one image attached
         """
 
         return self.get_replies(view_fields_only).annotate(images_count=Count(
             'images')).filter(images_count__gt=0)
 
     def add_tag(self, tag):
         """
         Connects thread to a tag and tag to a thread
         """
 
         self.tags.add(tag)
 
     def get_opening_post(self, only_id=False):
         """
         Gets the first post of the thread
         """
 
         query = self.get_replies().order_by('pub_time')
         if only_id:
             query = query.only('id')
         opening_post = query.first()
 
         return opening_post
 
     @cached_result
     def get_opening_post_id(self):
         """
         Gets ID of the first thread post.
         """
 
         return self.get_opening_post(only_id=True).id
 
     def __unicode__(self):
         return str(self.id)
 
     def get_pub_time(self):
         """
         Gets opening post's pub time because thread does not have its own one.
         """
 
         return self.get_opening_post().pub_time
 
     def delete(self, using=None):
         """
         Deletes thread with all replies.
         """
 
         for reply in self.get_replies().all():
             reply.delete()
 
         super(Thread, self).delete(using)
 
     def __str__(self):
         return 'T#{}/{}'.format(self.id, self.get_opening_post_id())