#27335: Avoid object save during QuerySet.update_or_create when there were no changes ----------------------------------------------+-------------------- Reporter: tonnzor | Owner: nobody Type: Cleanup/optimization | Status: new Component: Database layer (models, ORM) | Version: master Severity: Normal | Keywords: Triage Stage: Unreviewed | Has patch: 0 Easy pickings: 0 | UI/UX: 0 ----------------------------------------------+-------------------- Right now when you use QuerySet.update_or_create -- it always saves into DB even if there were no changes.
It would be great that if nothing is changed -- nothing is saved into DB. I found myself often reusing the same pattern in our projects. Use case: {{{#!python >>> from django.contrib.auth.models import User >>> User.objects.create(is_superuser=True, username='admin', is_active=True) # generate a use in DB to work with >>> # later in our code >>> user, created = User.objects.update_or_create(defaults={'is_active': True}, username='admin') # here an extra DB write though no data were changed }}} If you check the current code in master (https://github.com/django/django/blob/master/django/db/models/query.py#L477): {{{#!python try: obj = self.select_for_update().get(**lookup) except self.model.DoesNotExist: obj, created = self._create_object_from_params(lookup, params) if created: return obj, created for k, v in six.iteritems(defaults): setattr(obj, k, v() if callable(v) else v) obj.save(using=self.db) # HERE IT IS => always save }}} If object exists in DB, it would apply all attributes from `default` and save it even if there were no changes in values. We could do something like that: {{{#!python changed = False for k, v in six.iteritems(defaults): v = v() if callable(v) else v if v != getattr(obj, k): modified = True setattr(obj, k, v) if changed: obj.save(using=self.db) # save only if there were changes }}} If you think it is too complex for all use cases, we may put a flag for enabling / disabling this feature or have another method for this logic. -- Ticket URL: <https://code.djangoproject.com/ticket/27335> Django <https://code.djangoproject.com/> The Web framework for perfectionists with deadlines. -- You received this message because you are subscribed to the Google Groups "Django updates" group. To unsubscribe from this group and stop receiving emails from it, send an email to django-updates+unsubscr...@googlegroups.com. To post to this group, send email to django-updates@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/django-updates/050.4e2e256a5cdeb082cf9ea4ebfa1f9af2%40djangoproject.com. For more options, visit https://groups.google.com/d/optout.