How many rows were deleted?

Question

Is it possible to check how many rows were deleted by a query?

queryset = MyModel.object.filter(foo=bar)
queryset.delete()
deleted = ...

Or should I use transactions for that?

@transaction.commit_on_success
def delete_some_rows():
    queryset = MyModel.object.filter(foo=bar)
    deleted = queryset.count()
    queryset.delete()

PHP + MySQL example:

mysql_query('DELETE FROM mytable WHERE id < 10');
printf("Records deleted: %d\n", mysql_affected_rows());

Answer 1

There are many situations where you want to know how many rows were deleted, for example if you do something based on how many rows were deleted. Checking it by performing a COUNT creates extra database load and is not atomic.

The queryset.delete() method immediately deletes the object and returns the number of objects deleted and a dictionary with the number of deletions per object type. Check the docs for more details: https://docs.djangoproject.com/en/stable/topics/db/queries/#deleting-objects