Question

I have a django application with a model named TestCase. There are 9 instances of the model currently stored in the DB, which I can see by running TestCase.objects.all() in the shell, and they’re also being displayed correctly in my views.

However, in a management command I’m running, the same query (TestCase.objects.all()) consistently returns an empty list instead. I have imported the model correctly, and the management command is even able to add entries to the database without any problem, so reading back from the database shouldn’t be a problem.

Any ideas on what could be causing this?

Some context: The django app is a frontend to display and manage testcases. The management command reads in the results from the test into the DB. I need to access the DB in the management command to incorporate test runs into the app – if a testcase provides a test run (an integer) it is used, but if it does not, then the command sets the test run to one plus the max test run present in the app already – this is where I need to access the DB (using something like TestCase.objects.all().aggregate(Max('test_run'))).

I’m using Django 1.4.

This is the management command:

from django.core.management.base import NoArgsCommand
from django.core.management.base import AppCommand, CommandError
from mainapp.models import TestCase
from django.utils import timezone
from django.db.utils import IntegrityError
from django.conf import settings
from django.core import management
from django.db.models import Max 

import cPickle
import errno

class Command(NoArgsCommand):
  def handle_noargs(self, **options):
    management.call_command('reset', 'mainapp', interactive=False) 
    print "ALL: %s" % TestCase.objects.all()
    self.traverse()

  def traverse(self):
    ...

the output is ALL: []. I’ve omitted the source of the traverse() method, but the problem is visible before that, so it shouldn’t impact anything.

Here’s the output from the shell showing the instances in the DB:

[as@as-mac  ui]$ pm shell
Python 2.6.1 (r261:67515, Jun 24 2010, 21:47:49) 
[GCC 4.2.1 (Apple Inc. build 5646)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> from mainapp.models import TestCase
>>> TestCase.objects.all()
[<TestCase: internet explorer 8 on WIN7 at https://www.google.com/ >, <TestCase:     internet explorer 8 on WIN7 at https://www.google.com/ >, <TestCase: internet explorer 8 on WIN7 at https://www.google.com/search?q=mooo >, <TestCase: internet explorer 8 on WIN7 at https://www.google.com/search?q=mooo >, ...]
>>> TestCase.objects.count()
454

Please feel free to ask for more details!

Answer 1

The following line of your Command is resetting the database and clearing data:

management.call_command('reset', 'mainapp', interactive=False) 

If you remove this line, the record count in the shell and command will be equivalent.