Efficient way to update multiple fields of Django model object

Question

I'm trying to update user in Django database.

Fetched data is as follows :

fetched_data = {      'id': 1,      'first_name': 'John',      'last_name': 'Doe',      'phone': '+32 12',      'mobile_phone': '+32 13',      'email': '[email protected]',      'username': 'myusername' } 

I get the user with this id as follows :

old_user = User.objects.get(pk=fetched_data['id']) 

If I update the user as follows :

old_user.username = fetched_data['username'] old_user.first_name = fetched_data['first_name'] ...... old_user.save() 

it works fine, but I do not want to do it for every record, thus I tried something like :

for fetched_data_key in fetched_data:     old_user.fetched_data_key = fetched_data['fetched_data_key']     //old_user[fetched_data_key] = fetched_data['fetched_data_key'] --- I tried this way to     old_user.save() 

But that doesn't work. Any idea how can I update the user without doing it for every record?

Answer 1

You can update a row in the database without fetching and deserializing it; update() can do it. E.g.:

User.objects.filter(id=data['id']).update(email=data['email'], phone=data['phone']) 

This will issue one SQL update statement, and is much faster than the code in your post. It will never fetch the data or waste time creating a User object.

You cannot, though, send a whole bunch of update data to the SQL database and ask it to map it to different rows in one go. If you need a massive update like that done very quickly, your best bet is probably inserting the data into a separate table and then update it form a select on that table. Django ORM does not support this, as far as I can tell.