Search code examples
djangoinheritancemulti-table

Django Multi-table Inheritance, Django-model-utils errors

I am working on a hobby project for my garage shop. I was directed to django-model-utils for what I need. (I have serial CNC machines, serial machines have two flow control methods)

I have a parent class of SerialMachine (defines address, baud rate, generic RS-232 definition)

Then I have HardwareFlowControlMachine model which inherits from SerialMachine (defines CTS/DTR/etc)

So when I put machine name into a form (say machine 001) I have a function that get's machine settings.

def getMachineSettings(machine):

    from src.apps.cnc.models import SerialMachine

    machineSettings = SerialMachine.objects.get(machineName=machine).select_subclasses()

    return machineSettings

I get this exception:

  DatabaseError: no such column: cnc_hardwareflowcontrolmachine.serialmachine_ptr_id

Now for testing I only have one machine in SoftwareFlowControlMachine (none in Hardware)

I thought maybe HardwareFlowControlMachine needed at least one object for whatever reason. So when I go to /admin/ and try to add a machine to either SoftwareFlowControlMachine or HardwareFlowControlMachine I get this exception:

HardwareFlowControlMachine:

DatabaseError at /admin/cnc/hardwareflowcontrolmachine/

no such column: cnc_hardwareflowcontrolmachine.serialmachine_ptr_id

Request Method:     GET
Request URL:    http://127.0.0.1:8000/admin/cnc/hardwareflowcontrolmachine/
Django Version:     1.4
Exception Type:     DatabaseError
Exception Value:    

no such column: cnc_hardwareflowcontrolmachine.serialmachine_ptr_id

Exception Location:     C:\Python27\lib\site-packages\django\db\backends\sqlite3\base.py in execute, line 337
Python Executable:  C:\Python27\python.exe
Python Version:     2.7.2

SoftwareFlowControlMachine:

DatabaseError at /admin/cnc/softwareflowcontrolmachine/

no such column: cnc_softwareflowcontrolmachine.serialmachine_ptr_id

Request Method:     GET
Request URL:    http://127.0.0.1:8000/admin/cnc/softwareflowcontrolmachine/
Django Version:     1.4
Exception Type:     DatabaseError
Exception Value:    

no such column: cnc_softwareflowcontrolmachine.serialmachine_ptr_id

Exception Location:     C:\Python27\lib\site-packages\django\db\backends\sqlite3\base.py in execute, line 337
Python Executable:  C:\Python27\python.exe
Python Version:     2.7.2

Let me know if I need to provide more info. I am really not sure what I am missing

Solution

  • I got it working. I'm still unclear on why it happened though. A mistake I made is instead of 

     machineSettings = SerialMachine.objects.get(machineName=machine).select_subclasses()

    I needed this

     machineSettings = SerialMachine.objects.get_subclass(machineName=machine)

    I also just deleted my database and remade it.

    Hope this helps others too