在保存时跳过字段（Django模型，插入和更新）

Question

Given PostgreSQL 9.2.10, Django 1.8, python 2.7.5, the following model:

class soapProdAPI(models.Model):
    soap_id = models.PositiveIntegerField(primary_key=True)
    soap_host = models.CharField(max_length=20)
    soap_ip = models.GenericIPAddressField(default='0.0.0.0')
    soap_asset = models.CharField(max_length=20)
    soap_state = models.CharField(max_length=20)

And the following code:

tableProdSoap = soapProdQuery()


@periodic_task(run_every=timedelta(minutes=2))
def saveSoapProd():
    tableProdSoap = soapProdQuery()
    if tableProdSoap != None:
        for item in tableProdSoap:
            commit = soapProdAPI(soap_id=item[0], soap_host=item[1], soap_asset=item[2], soap_state=item[3])
            commit.save()
    saveSoapNullIP()

To answer Josué Padilla's question:

@task
def saveSoapNullIP():
    missingIP = soapProdAPI.objects.filter(soap_ip='0.0.0.0')
    if missingIP:
        for record in missingIP:
            if str(record.soap_host).lower().startswith('1a'):
                fqdn = str(record.soap_host) + 'stringvaluehere'
            elif str(record.soap_host).lower().startswith('1b'):
                fqdn = str(record.soap_host) + 'stringvaluehere'
            elif str(record.soap_host).lower().startswith('1c'):
                fqdn = str(record.soap_host) + 'stringvaluehere'
            else:
                fqdn = str(record.soap_host) + 'stringvaluehere'
            try:
                hostIp = check_output('host %s' % fqdn, shell=True)
                hostIp = hostIp.split()[-1]
            except:
                hostIp = '0.0.0.0'
            record.soap_ip = hostIp
            record.save(update_fields=['soap_ip'])

My soapProdQuery only returns these 4 fields where there is a 5th field in the model ( soap_ip ). I know it is probably not the best way to do it but I have a separate block of code that queries the db for None values in soap_ip runs a subprocess host on them and saves it back with the ip address (The number of rows returned/updated should get smaller each pass through, as opposed to putting the logic for doing a host lookup into the request/this celery task itself which would run every API request. I have tried this already, it takes FOREVER to return the completed data.). The soap API I query does not provide the IP or I would grab it that way obviously. This all runs as background tasks using celery to make it invisible/seamless to the web user.

The issue I run into is that every time the saveSoapProd() runs it overwrites the previous soap_ip field with '0.0.0.0' thus negating the work of my other function. The other issue is that I cannot force_insert or force_update as I need both functionalities with this. My question is this: is there a way to selectively update/insert at the same time and completely exclude doing anything to the soap_ip each time saveSoapProd() runs? Any and all help is greatly appreciated. Thank you in advance.

** EDIT 1 **

I may or may not have found a solution in update_or_create or get_or_create , however I am unsure on the exact usage. The docs have me slightly confused.

** EDIT 2 **

I guess get_or_create is a bust. Works first pass through but every save after that fails with this:

Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "<console>", line 8, in saveSoapProd
  File "/lib/python2.7/site-packages/django/db/models/base.py", line 690, in save
    % ', '.join(non_model_fields))
ValueError: The following fields do not exist in this model or are m2m fields: soap_id

Here is the code:

@periodic_task(run_every=timedelta(minutes=2))
def saveSoapProd():
    tableProdSoap = soapProdQuery()
    if tableProdSoap != None:
        for item in tableProdSoap:
            obj, created = soapProdAPI.objects.get_or_create(soap_id=item[0], defaults={'soap_host': item[1], 'soap_asset': item[2], 'soap_state': item[3]})
            if created == False:
                commit = soapProdAPI(soap_id=item[0], soap_host=item[1], soap_asset=item[2], soap_state=item[3])
                commit.save(update_fields=['soap_id', 'soap_host', 'soap_asset', 'soap_state'])

I will be honest, I am not entirely sure what is causing this error.

---

** EDIT 3/CURRENT SOLUTION **

I was able to resolve my own issue by modifying my model and my task function. The solution uses get_or_create, but you could easily extrapolate how to use update_or_create from the solution provided. See the selected answer below for a coded example.

---

** TLDR **

I want to do a .save() where it may need to do a insert for new records or update for changed records WITHOUT touching the soap_ip field (no insert_only or update_only ).

Answer 1

I don't know if you already knew this, but you can override the save() function of your model.

class soapProdAPI(models.Model):
    soap_id = models.PositiveIntegerField(primary_key=True)
    soap_host = models.CharField(max_length=20)
    soap_ip = models.GenericIPAddressField(default='0.0.0.0')
    soap_asset = models.CharField(max_length=20)
    soap_state = models.CharField(max_length=20)

    # Override save
    def save(self, *args, **kwargs):
        if self.soap_ip != '0.0.0.0':
          self.soap_ip = your_ip # Here you can  get your old IP an save that instead of 0.0.0.0

EDIT

You are getting

ValueError: The following fields do not exist in this model or are m2m fields: soap_id

Because you are trying to update soap_id , that field is defined as your model's primary key, so it is immutable when updating. That's why it crashes when you do:

commit.save(update_fields=['soap_id', 'soap_host', 'soap_asset', 'soap_state'])

Try removing soap_id from update_fields .

Answer 2

Solved my own issue without modifying the save method by making the following changes to my model:

class soapProdAPI(models.Model):
    soap_id = models.PositiveIntegerField(unique=True, null=False)
    soap_host = models.CharField(max_length=20)
    soap_ip = models.GenericIPAddressField(default='0.0.0.0')
    soap_asset = models.CharField(max_length=20)
    soap_state = models.CharField(max_length=20)

and my task:

def saveSoapProd():
    tableProdSoap = soapProdQuery()
    if tableProdSoap != None:
        for item in tableProdSoap:
            try:
                obj, created = soapProdAPI.objects.get_or_create(soap_id=item[0], defaults={'soap_host': item[1], 'soap_asset': item[2], 'soap_state': item[3]})
                if created == False:
                    obj.soap_host  = item[1]
                    obj.soap_asset = item[2]
                    obj.soap_state = item[3]
                    obj.save(update_fields=['soap_host', 'soap_asset', 'soap_state'])
            except:
                continue
    saveSoapMissingIP()

EDIT

Just noticed Josué Padilla's response, which was in fact part of my problem that I solved with this answer. Thank you to Josué for all of your help.