boards/management/commands/cleanusers.py

from datetime import datetime, timedelta
from django.core.management import BaseCommand
from django.db import transaction
from django.db.models import Count
from boards.models import User, Post

__author__ = 'neko259'

OLD_USER_AGE_DAYS = 90


class Command(BaseCommand):
    help = 'Removes empty users (that don\'t have posts or tags'

    @transaction.atomic
    def handle(self, *args, **options):
        old_registration_date = datetime.now().date() - timedelta(
            OLD_USER_AGE_DAYS)

        old_users = User.objects.annotate(tags_count=Count('fav_tags')).filter(
            tags_count=0).filter(registration_time__lt=old_registration_date)
        deleted_users = 0
        for user in old_users:
            if not Post.objects.filter(user=user).exists():
                self.stdout.write('Deleting user %s' % user.user_id)
                user.delete()
                deleted_users += 1

        self.stdout.write('Deleted %d users' % deleted_users)