如何更新模型中所有对象的参数-Django

Question

I want to update a parameter in a Django model for all objects in the DB. The values will be different for each object, and I'm trying to work out whether I can do this as a batch update, or whether I have to iterate through each item and save each one separately.

The model I'm using is an extension of the Django auth user model:

from django.contrib.auth.models import User
from django.db import models

class Profile(models.Model):
    user = models.OneToOneField(User)
    position = models.PositiveIntegerField(null=False, default=0)

If I get all objects as follows:

queryset = User.objects.all()

then loop through these and update position :

for user in queryset:
    user.position = #SOME FUNCTION

do I have to do user.save() within the for loop? Or can I update each item and then save all at once to the DB?

Answer 1

Django doesn't have a bulk update but what you can do is use an atomic transaction to improve performance by committing all update statements once.

from django.db import transaction

with transaction.atomic():
    for user in queryset:
        user.position = #SOME FUNCTION
        user.save()

There will still be len(queryset) inserts but they will be grouped into a single transaction.