问题
What is the Django way to copy and paste Queryset except iterating over records and cloning/saving? E.g. a set of records from table A needs to be selected, some field updated and records inserted back to the original table? A sample use case is adding subscribers from mailing list A to mailing list B. Should it be just a loop iterating over QuerySet and cloning/saving record by record, or there is some method for group operation?
回答1:
Django 1.4 has bulk_create method that does his job in 1 sql query
回答2:
It doesn't sound like you want to clone or copy these records - that's something you should avoid in a normalized database anyway.
If you just want to update a single field, then you can do that with the update queryset method:
MyModel.objects.filter(mailing_list=list_a).update(mailing_list=list_b)
If you're talking about adding them to a different M2M relationship, then you can do that simply:
mailing_list_b.users.add(*MyModel.objects.filter(mailing_list=list_a))
回答3:
In Django 1.3 the solution is to iterate QuerySet and create copies like this:
from copy import deepcopy
old_obj = deepcopy(obj)
old_obj.id = None
old_obj.save()
来源：https://stackoverflow.com/questions/10911416/django-copy-paste-queryset