file_cleanup.py

import os

from django.core.management.base import CommandError, LabelCommand
from django.utils.datastructures import SortedDict
from django_commands.utils import parse_apps_and_models

class Command(LabelCommand):
    args = '<upload-path> <appname.Model> [appname.Model] ...>'
    help = ("Cleans orphaned file field files from <upload-path>.\n"
            "'Orphaned' is defined as existing under <upload-path> "
            "but\nnot referenced by any file fields in given "
            "<appname.Model>s.")

    def handle_label(self, label, **options):
        upload_path, modelnames = label.split(' ', 1)
        # Order is important to avoid races.
        # Build list of files on disk first, in db second.
        filenames_on_disk = list_files(upload_path)

        filenames_in_database = set()
        for appname, modelname in parse_apps_and_models(modelnames):
            model = get_model_cls(appname, modelname)
            filefields = get_filefields(model)
            if not filefields:
                raise CommandError("Model %s.%s contains no file fields" %
                        (appname, modelname))
            for filefield in filefields:
                kwargs = {filefield: ''}
                qs = model.objects.exclude(**kwargs).values_list(
                        filefield, flat=True)
                filenames_in_database.update(os.path.join(upload_path, name)
                        for name in qs)

        if not filenames_in_database:
            warn("No files in database")
            return

        db_has_extra_files = filenames_in_database.issubset(filenames_on_disk)
        if db_has_extra_files:
            # Avoid erasing files accidentally.
            # There's a minor race here: subset check may fail if a file is
            # added while the script runs.
            raise CommandError("Database filenames are not a "
                    "subset of actual filenames on disk. Will not risk "
                    "erasing arbitrary files, exiting.")

        dangling_files = filenames_on_disk - filenames_in_database
        remove_files(dangling_files)