How to use select_for_update to 'get' a Query in Django?

python django django-queryset
Indradhanush Gupta picture Indradhanush Gupta · Jun 18, 2013 · Viewed 23.8k times · Source

As the Django Documentation says, select_for_update returns a Queryset. But get does not. Now I have a query which I am sure is going to return only one tuple. But I also need to acquire locks for this transaction. So I am doing something like:

ob = MyModel.objects.select_for_update().filter(some conditions)

Now I need to modify some values of ob. But ob is a Queryset. This seems pretty simple, but beats me. I'm pretty new to Django. Some advice please.

Answer

Yuji 'Tomita' Tomita picture Yuji 'Tomita' Tomita · Jun 18, 2013

Just call get, slice it, etc. and save as usual. The lock is in place through the transaction.

ob = MyModel.objects.select_for_update().get(pk=1)

Any changes are committed at the end of the transaction (which by default through 1.5 is per-request)

Related questions

How do I do a not equal in Django queryset filtering?

In Django model QuerySets, I see that there is a __gt and __lt for comparative values, but is there a __ne or != (not equals)? I want to filter out using a not equals. For example, for Model: bool a; int …

Read More
How do I filter query objects by date range in Django?

I've got a field in one model like: class Sample(models.Model): date = fields.DateField(auto_now=False) Now, I need to filter the objects by a date range. How do I filter all the objects that have a date …

Read More
How can I filter a Django query with a list of values?

I'm sure this is a trivial operation, but I can't figure out how it's done. There's got to be something smarter than this: ids = [1, 3, 6, 7, 9] for id in ids: MyModel.objects.filter(pk=id) I'm looking to get them all in …

Read More