Implement caching for homepage data and signals to improve performance

static/website/templates/ajax-keyword-search.html

@@ -63,16 +63,16 @@
         </td>
 
         <td>
-            {{ question.views}}
+            {{ question.views }}
         </td>
 
         <td>
-            {{ question.answer_set.count }}
+            {{ question.total_answers }}
         </td>
 
         <td>
-                <span class="title" data-toggle="tooltip" data-placement="top" title="{{ question.user }}">
-                {{ question.user|truncatechars:10 }}
+            <span class="title" data-toggle="tooltip" data-placement="top" title="{{ question.cached_user|default:question.user }}">
+                {{ question.cached_user|default:question.user|truncatechars:10 }}
             </span>
         </td>
 

static/website/templates/ajax-time-search.html

@@ -61,16 +61,16 @@
         </td>
 
         <td>
-            {{ question.views}}
+            {{ question.views }}
         </td>
 
         <td>
-            {{ question.answer_set.count }}
+            {{ question.total_answers }}
         </td>
 
         <td>
-                <span class="title" data-toggle="tooltip" data-placement="top" title="{{ question.user }}">
-                {{ question.user|truncatechars:10 }}
+            <span class="title" data-toggle="tooltip" data-placement="top" title="{{ question.cached_user|default:question.user }}">
+                {{ question.cached_user|default:question.user|truncatechars:10 }}
             </span>
         </td>
 

static/website/templates/filter.html

@@ -82,16 +82,16 @@ <h5>
             </td>
 
             <td>
-                {{ question.views}}
+                {{ question.views }}
             </td>
-
+            
             <td>
-                {{ question.answer_set.count }}
+                {{ question.total_answers }}
             </td>
-
+           
             <td>
-                    <span class="title" data-toggle="tooltip" data-placement="top" title="{{ question.user }}">
-                    {{ question.user|truncatechars:10 }}
+                <span class="title" data-toggle="tooltip" data-placement="top" title="{{ question.cached_user|default:question.user }}">
+                    {{ question.cached_user|default:question.user|truncatechars:10 }}
                 </span>
             </td>
 

static/website/templates/get-question.html

@@ -136,7 +136,7 @@ <h5>Question</h5>
             </small>
 
             <span class="user">
-                {{ question.user }}
+                {{ question.cached_user|default:question.user }}
             </span>
         </span>
     </div> <!-- /.question -->
@@ -169,7 +169,7 @@ <h4><u>Answers:</u></h4>
                 </small>
 
                 <span class="user">
-                    {{ answer.user }}
+                    {{ answer.cached_user|default:answer.user }}
                 </span>
             </span>
             {% if user|can_edit:answer  %}
@@ -199,7 +199,7 @@ <h4><u>Answers:</u></h4>
                         </small>
 
                         <span class="user">
-                            {{ comment.user }}
+                            {{ comment.cached_user|default:comment.user }}
                         </span>
                     </span>
                     {% if user|can_edit:comment %}

static/website/templates/notifications.html

@@ -7,7 +7,7 @@ <h4 class="pull-left">Notifications</h4>
     </a>
     <div class="clearfix"></div> 
     {% for notification in notifications %}
-        {% get_notification notification.id %}
+        {% get_notification notification %}
     {% endfor %}
 {% endblock %}
 

static/website/templates/questions.html

@@ -68,16 +68,16 @@ <h5>
             </td>
 
             <td class="col-md-1">
-                {{ question.views}}
+                {{ question.views }}
             </td>
 
             <td class="col-md-1">
-                {{ question.answer_set.count }}
+                {{ question.total_answers }}
             </td>
 
             <td class="col-md-1">
-                <span class="title" data-toggle="tooltip" data-placement="top" title="{{ question.user }}">
-                    {{ question.user|truncatechars:10 }}
+                <span class="title" data-toggle="tooltip" data-placement="top" title="{{ question.cached_user|default:question.user }}">
+                    {{ question.cached_user|default:question.user|truncatechars:10 }}
                 </span>
             </td>
         </tr>

static/website/templates/recent-questions.html

@@ -1,9 +1,7 @@
-{% extends 'website/templates/base.html' %}
 {% load static %}
 {% load count_tags %}
 
-{% block content %}
-    <h4><u>Recent Questions</u></h4>
+<h4><u>Recent Questions</u></h4>
     <table class="table table-bordered table-hover">
         <th> FOSS </th>
         <th> Tutorial</th>
@@ -65,16 +63,16 @@ <h4><u>Recent Questions</u></h4>
             </td>
 
             <td>
-                {{ question.views}}
+                {{ question.views }}
             </td>
 
             <td>
-                {{ question.answer_set.count }}
+                {{ question.total_answers }}
             </td>
 
             <td>
-                <span class="title" data-toggle="tooltip" data-placement="top" title="{{ question.user }}">
-                    {{ question.user|truncatechars:10 }}
+                <span class="title" data-toggle="tooltip" data-placement="top" title="{{ question.cached_user|default:question.user }}">
+                    {{ question.cached_user|default:question.user|truncatechars:10 }}
                 </span>
             </td>
         </tr>
@@ -96,11 +94,6 @@ <h4><u>Recent Questions</u></h4>
             {% endfor %}
         </ul>
     {% endif %}
-
-{% endblock %}
-
-{% block javascript %}
 <script>
     $('span').tooltip();
 </script>
-{% endblock %}

website/models.py

@@ -21,12 +21,22 @@ class Question(models.Model):
     # votes = models.IntegerField(default=0)
 
     def user(self):
+        cached_username = getattr(self, "cached_user", None)
+        if cached_username is not None:
+            return cached_username
         user = User.objects.get(id=self.uid)
-        return user.username
+        username = user.username
+        self.cached_user = username
+        return username
 
     def last_post_user(self):
+        cached_username = getattr(self, "cached_last_post_user", None)
+        if cached_username is not None:
+            return cached_username
         user = User.objects.filter(id=self.last_post_by).first()
-        return user.username if user else "Unknown User"
+        username = user.username if user else "Unknown User"
+        self.cached_last_post_user = username
+        return username
 
     class Meta:
         get_latest_by = "date_created"
@@ -54,8 +64,13 @@ class Answer(models.Model):
     # votes = models.IntegerField(default=0)
 
     def user(self):
+        cached_username = getattr(self, "cached_user", None)
+        if cached_username is not None:
+            return cached_username
         user = User.objects.get(id=self.uid)
-        return user.username
+        username = user.username
+        self.cached_user = username
+        return username
 
 
 class AnswerVote(models.Model):
@@ -71,8 +86,13 @@ class AnswerComment(models.Model):
     date_modified = models.DateTimeField(auto_now=True)
 
     def user(self):
+        cached_username = getattr(self, "cached_user", None)
+        if cached_username is not None:
+            return cached_username
         user = User.objects.get(id=self.uid)
-        return user.username
+        username = user.username
+        self.cached_user = username
+        return username
 
 
 class Notification(models.Model):
@@ -84,7 +104,12 @@ class Notification(models.Model):
     date_created = models.DateTimeField(auto_now_add=True)
 
     def poster(self):
+        cached_username = getattr(self, "cached_poster", None)
+        if cached_username is not None:
+            return cached_username
         user = User.objects.get(id=self.pid)
-        return user.username
+        username = user.username
+        self.cached_poster = username
+        return username
 
 # CDEEP database created using inspectdb arg of manage.py

website/templatetags/count_tags.py

@@ -6,10 +6,16 @@
 register = template.Library()
 
 
-# Counts the number of questions in <category>
+# Counts the number of questions in <category>, cached for faster rendering
 def category_question_count(category):
-    category_question_count = Question.objects.filter(category=category).count()
-    return category_question_count
+    cache_key = f"stats:category_question_count:{category}"
+    count = cache.get(cache_key)
+    if count is not None:
+        return count
+
+    count = Question.objects.filter(category=category).count()
+    cache.set(cache_key, count, 300)
+    return count
 
 
 register.simple_tag(category_question_count)

website/templatetags/notify.py

@@ -5,16 +5,16 @@
 register = template.Library()
 
 
-def get_notification(nid):
-    notification = Notification.objects.get(pk=nid)
-    try:
-        question = Question.objects.get(pk=notification.qid)
-    except Question.DoesNotExist:
-        question =  None
-    try:
-        answer = Answer.objects.get(pk=notification.aid)
-    except Answer.DoesNotExist:
-        answer = None
+def get_notification(notification):
+    """
+    Render a single notification.
+
+    The view (`user_notifications`) attaches `cached_question`, `cached_answer`
+    and `cached_poster` attributes on each `Notification` instance so that this
+    tag does not need to perform any additional database queries.
+    """
+    question = getattr(notification, "cached_question", None)
+    answer = getattr(notification, "cached_answer", None)
     context = {
         'notification': notification,
         'question': question,

website/templatetags/sidebar_tags.py

@@ -1,13 +1,22 @@
 from django import template
+from django.db.models import Count
 
 from website.models import Question
 
 register = template.Library()
 
 
 def recent_questions():
-    recent_questions = Question.objects.all().order_by('-id')[:5]
-    return {'recent_questions': recent_questions}
+    recent_questions = (
+        Question.objects.all()
+        .annotate(total_answers=Count('answer'))
+        .order_by('-id')[:5]
+    )
+    return {
+        'questions': recent_questions,
+        'total': 10,
+        'marker': 0,
+    }
 
 
-register.inclusion_tag('website/templates/recent_questions.html')(recent_questions)
+register.inclusion_tag('website/templates/recent-questions.html')(recent_questions)