2. Bulk Updates

Django ships with an update() method to update data to the database.

This method is limited to updating data homogeneously– that is, all the values for the column(s) being updated is set to the same value throughout the queryset.

Django-bulkmodel adds to the functionality by providing a update_fields() method, which updates data heterogeneously– that is, the values for the column(s) being updated can have different values for each model instance in the queryset.

Suppose you have the following model:

from bulkmodel.models import BulkModel

class Foo(BulkModel):
    name = models.CharField(max_length=50, blank=False)
    value = models.IntegerField(null=False)

Using update you can change the value to be the same

foos = ... # a queryset

foos.update(value = 5)

Using update_fields you can update records to have different values for each item.

for foo in foos:
    # different value for each model instance in the queryset
    foo.value += randint(100, 200)

# update all fields that changed
foos.update_fields()

# or update just the value field
foos.update_fields('value')

Importantly, this will issue a single query against the database.

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See Queryset Reference for more details.