query optimization for homepage scroller

Author: ankitamk14

static/website/templates/index.html

@@ -27,22 +27,27 @@
 </script>
     <div id="carousel-container">
         <div class="carousel">
-            {% for category in categories %}
+            {% for item in slider_questions %}
                 <div>
                     <div class="thumbnail">
-                        {% with file=category|get_category_image %}
+                        {% with file=item.category|get_category_image %}
                             {% if file %}
-                                <img src="{% static category|get_category_image %}">
+                                <img src="{% static item.category|get_category_image %}">
                             {% else %}
-                                <div class="category-title">{{category}}</div>
+                                <div class="category-title">{{item.category}}</div>
                             {% endif %}
                         {% endwith %}
+
                         <div class="caption">
                             <small class="category">
-                                {{ category }}
+                                {{ item.category }}
                             </small>
-                            {% latest_question category %}
-                            <a class="btn btn-xs btn-block btn-success" href="{% url 'website:new_question' %}?category={{ category|urlencode }}">Ask new question</a>
+                                <small class="latest">
+                                    <a href="{% url 'website:get_question' item.id %}">{{ item.title }}</a>
+                                </small>
+                                <a class="btn btn-xs btn-block btn-primary" href="{% url 'website:filter' item.category %}">View previous questions</a>
+                            
+                            <a class="btn btn-xs btn-block btn-success" href="{% url 'website:new_question' %}?category={{ item.category|urlencode }}">Ask new question</a>
                         </div>
                     </div>
                 </div>

website/views.py

@@ -4,7 +4,7 @@
 from django.shortcuts import render, get_object_or_404
 from django.template.context_processors import csrf
 from django.contrib.auth.decorators import login_required
-from django.db.models import Q
+from django.db.models import Q, OuterRef, Subquery, Max, Count
 from django.core.mail import EmailMultiAlternatives
 from django.core.paginator import Paginator, EmptyPage, PageNotAnInteger
 from django.contrib.auth import get_user_model
@@ -17,7 +17,6 @@
 from website.templatetags.permission_tags import can_edit, can_hide_delete
 from spoken_auth.models import FossCategory
 from .sortable import SortableHeader, get_sorted_list, get_field_index
-from django.db.models import Count
 
 
 User = get_user_model()
@@ -32,10 +31,17 @@
 def home(request):
     questions = Question.objects.filter(status=1).order_by('date_created').reverse()[:100]
     active_questions = Question.objects.filter(status=1, last_active__isnull=False).order_by('last_active').reverse()[:100]
+
+    subquery = Question.objects.filter(category=OuterRef('category')).values('category').annotate(max_date=Max('date_created')).values('max_date')
+    slider_questions = Question.objects.filter(
+            date_created=Subquery(subquery)
+    ).order_by('category')
+    
     context = {
         'categories': categories,
         'questions': questions,
-        'active_questions':active_questions
+        'active_questions':active_questions,
+        'slider_questions': slider_questions
     }
     return render(request, "website/templates/index.html", context)