query speedups in query and serializers

helpdesk/query.py

@@ -1,10 +1,9 @@
 
 from base64 import b64decode, b64encode
-from django.db.models import Q
+from django.db.models import Q, Max
 from django.urls import reverse
 from django.utils.html import escape
 from django.utils.translation import gettext as _
-from django.db.models import Max
 from helpdesk.serializers import DatatablesTicketSerializer
 import json
 from model_utils import Choices
@@ -177,8 +176,7 @@ class __Query__:
         if order == 'desc':
             order_column = '-' + order_column
 
-        queryset = objects.all().order_by(order_by)
+        queryset = objects.annotate(last_followup=Max('followup__date')).order_by(order_by)
-        queryset = queryset.annotate(last_followup=Max('followup__date'))
         total = queryset.count()
 
         if search_value:  # Dead code currently

helpdesk/serializers.py

@@ -1,7 +1,7 @@
 from django.contrib.auth import get_user_model
 from django.contrib.humanize.templatetags import humanize
+from django.db.models import Max, F, Window
 from django.utils.timezone import localtime
-from django.core.exceptions import ObjectDoesNotExist
 from rest_framework import serializers
 from rest_framework.exceptions import ValidationError
 
@@ -75,12 +75,15 @@ class DatatablesTicketSerializer(serializers.ModelSerializer):
         return obj.kbitem.title if obj.kbitem else ""
         
     def get_last_followup(self, obj):
-        try:
+        followup = obj.followup_set.order_by().annotate(
-            followup = obj.followup_set.latest('date')
+            last_followup=Window(
-            followup = obj.followup_set.latest('date')        
+                expression=Max("date"),
-            return localtime(followup.date).strftime('%Y-%m-%d %H:%M:%S') if followup else ""
+                partition_by=[F("ticket_id"),],
-        except ObjectDoesNotExist:
+                order_by="-date"
-            return None  # Return None or an empty string if no follow-ups exist
+            )
+        ).values("last_followup").distinct().values_list("last_followup", flat=True)
+        # If there are no followups for the ticket then the result will be empty
+        return localtime(followup[0]).strftime('%Y-%m-%d %H:%M:%S') if followup else ""
         
     
 class FollowUpAttachmentSerializer(serializers.ModelSerializer):