Django: Increment blog entry view count by one. Is this efficient?

by

You can use F() objects for this.

Here is how you import F: from django.db.models import F

New in Django 1.1.
Calls to update can also use F() objects to update one field based on the value of another field in the model. This is especially useful for incrementing counters based upon their current value.

Entry.objects.filter(is_published=True).update(views=F('views')+1)

Although you can’t do an update on a sliced query set… edit: actually you can…

This can be done completely in django ORM. You need two SQL queries:

  1. Do your filter and collect a list of primary keys
  2. Do an update on a non-sliced query set of items matching any of those primary keys.

Getting the non-sliced query set is the hard bit. I wondered about using in_bulk but that returns a dictionary, not a query set. One would usually use Q objects to do complex OR type queries and that will work, but pk__in does the job much more simply.

latest_entry_ids = Entry.objects.filter(is_published=True)\
                                      .order_by('-date_published')
                                      .values_list('id', flat=True)[:10]  
non_sliced_query_set = Entry.objects.filter(pk__in=latest_entry_ids)  
n = non_sliced_query_set.update(views=F('views')+1)  
print n or 0, 'items updated'

Due to the way that django executes queries lazily, this results in just 2 database hits, no matter how many items are updated.

More Related Contents:

  1. OperationalError: database is locked
  2. multiple databases and multiple models in django
  3. Django persistent database connection
  4. How do you join two tables on a foreign key field using django ORM?
  5. How to make/use a custom database function in Django
  6. How to see the raw SQL queries Django is running?
  7. A QuerySet by aggregate field value
  8. How to move a model between two Django apps (Django 1.7)
  9. Count() vs len() on a Django QuerySet
  10. sqlite3.OperationalError: unable to open database file
  11. Race conditions in django
  12. What is your favorite solution for managing database migrations in django? [closed]
  13. django.core.exceptions.ImproperlyConfigured: Error loading MySQLdb module: No module named MySQLdb
  14. django makemigrations and migrate on heroku server don’t create tables
  15. Type error on Login using the ‘login()’ function
  16. String formatting: % vs. .format vs. f-string literal
  17. When should I (not) want to use pandas apply() in my code?
  18. Django URLs TypeError: view must be a callable or a list/tuple in the case of include()
  19. Django Rest Framework File Upload
  20. How can I filter a Django query with a list of values?
  21. Poor scaling of multiprocessing Pool.map() on a list of large objects: How to achieve better parallel scaling in python?
  22. Django 1.8 sending mail using gmail SMTP
  23. Why is `np.sum(range(N))` very slow?
  24. Is it better to use path() or url() in urls.py for django 2.0?
  25. No Module named django.core
  26. Running Scrapy spiders in a Celery task
  27. How to set and get session variable in django?
  28. How to assign a local file to the FileField in Django?
  29. How do you configure Django for simple development and deployment?
  30. Python if vs try-except

Leave a Comment