Writing a Django management command for a large batch job

# ======================================================================
# Q: How do you write a management command for a large job?
#
# Batches with small transactions, --dry-run, progress in the output, and
# idempotent so that it can be rerun if interrupted.
# ======================================================================

class Command(BaseCommand):
    help = 'Recalculate customer totals'

    def add_arguments(self, parser):
        parser.add_argument('--batch-size', type=int, default=1000)
        parser.add_argument('--dry-run', action='store_true')

    def handle(self, *args, batch_size, dry_run, **options):
        qs = Customer.objects.order_by('pk')
        for i, chunk in enumerate(read_in_chunks(qs, batch_size), 1):
            if not dry_run:
                with transaction.atomic():
                    recalc_totals(chunk)
            self.stdout.write(f'batch {i} done')