Orphaned Public List Notifications

query.py

import sys
from django.core.paginator import Paginator
from notifications.constants import NOTIFY_UPDATE
from lists.models import List
from lists.permissions.permissions import can_read_wishlist_via_shared_group
from notifications.models import Notification

list_ids = List.objects.filter(privacy_level=List.PUBLIC).values_list('id', flat=True)
objs = Notification.objects.filter(sub_type=NOTIFY_UPDATE, object_id__in=list_ids)

# Result: 553,742 notifications, not yet filtered on owner's access

problem_objs = []
len_objs = objs.count()
chunk_size = 25000
i = 0

print(f'{len_objs} Notification objects total are processable.')

paginator = Paginator(objs, chunk_size)
for page_number in paginator.page_range:
    page = paginator.page(page_number)
    for n, obj in enumerate(page.object_list):
        print(f'{i + n+1}/{len_objs}', end='\r')
        if not can_read_wishlist_via_shared_group(obj.content_object, obj.owner):
            problem_objs.append(obj.id)
    i += chunk_size

to_delete = Notification.objects.filter(id__in=problem_objs)

confirmation = input(f'Are you sure you want to delete the selected {to_delete.count()} notifications? (y/n): ')
if confirmation.lower() == 'y':
    result = to_delete.delete()
    print(result)
else:
    print('Deletion cancelled.')