[Answered ]-Model save update only specific fields

by

2👍

✅

This is not how you’re supposed to update.

Model(**param_dict["Model"]).save()

You’re creating a new instance with the same id. Instead, you should get the instance, and then update it appropriately.

m = Model.objects.get(id=param_dict['id'])
m.field = param_dict['some_field']
m.save()

Or, you can use the Manager update method:

Model.objects.filter(id=param_dict['id']).update(**param_dict['Model'])

There’s also the get_or_create method if you’re not sure whether or not the record already exists.

You can try using a REST framework, like tasty-pie or django-rest-framework, which might alleviate some problems you’re having.

Edit:

A brief summary about how save works in django. This is what I meant about whether or not an INSERT or an UPDATE is happening. Unless your post_data dict contains empty values for all the fields, read the documentation on how save works for a more thorough understanding of how django works.

So, what is happening in your case is this:

dict = {'id': 1, 'field1': 'my_value'}
m = Model(**dict)
m.id       # 1
m.field1   # my_value
m.field2   # None (because you haven't set it, it defaults to None
m.save()   # UPDATEs the existing instance with id 1 with ALL of the values of `m`

So, you’re saving an instance that contains None values. That’s why I’m suggesting you do a get, so that all the correct values are filled, before saving to the database.

👤Josh Smeaton

0👍

Maybe you shoul use some function like this:

def insert_or_update(param_dict):
    pk = param_dict.get('pk', None)
    if pk:
        Model.objects.filter(pk=pk).update(**param_dict)
    else:
        Model(**param_dict)
        Model.save()
👤genry

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