Fork of Django's dumpdata management command with an option to select related models to dump as well.

dumpdata_related.py

from django.core.exceptions import ImproperlyConfigured
from django.core.management.base import BaseCommand, CommandError
from django.core import serializers
from django.db import router, DEFAULT_DB_ALIAS
from django.utils.datastructures import SortedDict

from optparse import make_option

class Command(BaseCommand):
    option_list = BaseCommand.option_list + (
        make_option('--format', default='json', dest='format',
            help='Specifies the output serialization format for fixtures.'),
        make_option('--indent', default=None, dest='indent', type='int',
            help='Specifies the indent level to use when pretty-printing output'),
        make_option('--database', action='store', dest='database',
            default=DEFAULT_DB_ALIAS, help='Nominates a specific database to dump '
                'fixtures from. Defaults to the "default" database.'),
        make_option('-e', '--exclude', dest='exclude',action='append', default=[],
            help='An appname or appname.ModelName to exclude (use multiple --exclude to exclude multiple apps/models).'),
        make_option('-n', '--natural', action='store_true', dest='use_natural_keys', default=False,
            help='Use natural keys if they are available.'),
        make_option('-a', '--all', action='store_true', dest='use_base_manager', default=False,
            help="Use Django's base manager to dump all models stored in the database, including those that would otherwise be filtered or modified by a custom manager."),
        make_option('--pks', dest='primary_keys', help="Only dump objects with "
            "given primary keys. Accepts a comma seperated list of keys. "
            "This option will only work when you specify one model."),
        make_option('--related', dest='related'),
    )
    help = ("Output the contents of the database as a fixture of the given "
            "format (using each model's default manager unless --all is "
            "specified).")
    args = '[appname appname.ModelName ...]'

    def handle(self, *app_labels, **options):
        from django.db.models import get_app, get_apps, get_model

        format = options.get('format')
        indent = options.get('indent')
        using = options.get('database')
        excludes = options.get('exclude')
        show_traceback = options.get('traceback')
        use_natural_keys = options.get('use_natural_keys')
        use_base_manager = options.get('use_base_manager')
        pks = options.get('primary_keys')
        related = options.get('related')

        if pks:
            primary_keys = pks.split(',')
        else:
            primary_keys = []

        if related:
            related = related.split(',')

        excluded_apps = set()
        excluded_models = set()
        for exclude in excludes:
            if '.' in exclude:
                app_label, model_name = exclude.split('.', 1)
                model_obj = get_model(app_label, model_name)
                if not model_obj:
                    raise CommandError('Unknown model in excludes: %s' % exclude)
                excluded_models.add(model_obj)
            else:
                try:
                    app_obj = get_app(exclude)
                    excluded_apps.add(app_obj)
                except ImproperlyConfigured:
                    raise CommandError('Unknown app in excludes: %s' % exclude)

        if len(app_labels) == 0:
            if primary_keys:
                raise CommandError("You can only use --pks option with one model")
            app_list = SortedDict((app, None) for app in get_apps() if app not in excluded_apps)
        else:
            if len(app_labels) > 1 and primary_keys:
                raise CommandError("You can only use --pks option with one model")
            app_list = SortedDict()
            for label in app_labels:
                try:
                    app_label, model_label = label.split('.')
                    try:
                        app = get_app(app_label)
                    except ImproperlyConfigured:
                        raise CommandError("Unknown application: %s" % app_label)
                    if app in excluded_apps:
                        continue
                    model = get_model(app_label, model_label)
                    if model is None:
                        raise CommandError("Unknown model: %s.%s" % (app_label, model_label))

                    if app in app_list.keys():
                        if app_list[app] and model not in app_list[app]:
                            app_list[app].append(model)
                    else:
                        app_list[app] = [model]
                except ValueError:
                    if primary_keys:
                        raise CommandError("You can only use --pks option with one model")
                    # This is just an app - no model qualifier
                    app_label = label
                    try:
                        app = get_app(app_label)
                    except ImproperlyConfigured:
                        raise CommandError("Unknown application: %s" % app_label)
                    if app in excluded_apps:
                        continue
                    app_list[app] = None

        if related:
            if len(app_list) != 1 or len(app_list.values()[0]) != 1:
                raise CommandError("you can only use --related option with one model")

        # Check that the serialization format exists; this is a shortcut to
        # avoid collating all the objects and _then_ failing.
        if format not in serializers.get_public_serializer_formats():
            try:
                serializers.get_serializer(format)
            except serializers.SerializerDoesNotExist:
                pass

            raise CommandError("Unknown serialization format: %s" % format)

        def get_objects():
            # Collate the objects to be serialized.
            for model in sort_dependencies(app_list.items()):
                if model in excluded_models:
                    continue
                if not model._meta.proxy and router.allow_syncdb(using, model):
                    if use_base_manager:
                        objects = model._base_manager
                    else:
                        objects = model._default_manager

                    queryset = objects.using(using).order_by(model._meta.pk.name)
                    if primary_keys:
                        queryset = queryset.filter(pk__in=primary_keys)
                        if related:
                            queryset = queryset.select_related()
                    serialized_objects = set()
                    for obj in queryset.iterator():
                        if related:
                            for rel_expression in related:
                                for rel_obj in get_related_objects(obj, rel_expression):
                                    if rel_obj not in serialized_objects:
                                        serialized_objects.add(rel_obj)
                                        yield rel_obj
                        if obj not in serialized_objects:
                            yield obj

        def get_related_objects(obj, rel_expression):
            expressions = rel_expression.split('.')
            nb_expressions = len(expressions)
            rel_objs = [obj]
            for i, fieldname in enumerate(expressions):
                last_iteration = (i == (nb_expressions - 1)) and True or False
                rel_objs = [getattr(rel_obj, fieldname) for rel_obj in rel_objs
                            if getattr(rel_obj, fieldname)]
                # FK is null, don't go any further.
                if not rel_objs:
                    return rel_objs
                # M2M.
                if hasattr(rel_objs[0], "all"):
                    rel_objs = [rel for rel_obj in rel_objs for rel in rel_obj.all()]
                    if use_natural_keys and last_iteration and \
                       hasattr(obj, 'natural_key') and len(rel_objs):
                        # Search a potential FK to main object. If such
                        # relation exists, obj is inserted to respect the
                        # dependency order.
                        rel_obj = rel_objs[0]
                        for field in rel_obj._meta.fields:
                            if field.rel and field.rel.to == obj.__class__ and \
                               getattr(rel_obj, field.name) == obj:
                                rel_objs.insert(0, obj)
                                break

                # Retrieve OneToOne relations if such exists.
                if len(rel_objs) and last_iteration:
                    parents = rel_objs[0]._meta.get_parent_list()
                    if parents:
                        parents = [parent.objects.get(pk=rel.pk)
                                   for rel in rel_objs for parent in parents]
                        rel_objs = parents + rel_objs
            return rel_objs

        try:
            self.stdout.ending = None
            serializers.serialize(format, get_objects(), indent=indent,
                    use_natural_keys=use_natural_keys, stream=self.stdout)
        except Exception as e:
            if show_traceback:
                raise
            raise CommandError("Unable to serialize database: %s" % e)


def sort_dependencies(app_list):
    """Sort a list of app,modellist pairs into a single list of models.

    The single list of models is sorted so that any model with a natural key
    is serialized before a normal model, and any model with a natural key
    dependency has it's dependencies serialized first.
    """
    from django.db.models import get_model, get_models
    # Process the list of models, and get the list of dependencies
    model_dependencies = []
    models = set()
    for app, model_list in app_list:
        if model_list is None:
            model_list = get_models(app)

        for model in model_list:
            models.add(model)
            # Add any explicitly defined dependencies
            if hasattr(model, 'natural_key'):
                deps = getattr(model.natural_key, 'dependencies', [])
                if deps:
                    deps = [get_model(*d.split('.')) for d in deps]
            else:
                deps = []

            # Now add a dependency for any FK or M2M relation with
            # a model that defines a natural key
            for field in model._meta.fields:
                if hasattr(field.rel, 'to'):
                    rel_model = field.rel.to
                    if hasattr(rel_model, 'natural_key') and rel_model != model:
                        deps.append(rel_model)
            for field in model._meta.many_to_many:
                rel_model = field.rel.to
                if hasattr(rel_model, 'natural_key') and rel_model != model:
                    deps.append(rel_model)
            model_dependencies.append((model, deps))

    model_dependencies.reverse()
    # Now sort the models to ensure that dependencies are met. This
    # is done by repeatedly iterating over the input list of models.
    # If all the dependencies of a given model are in the final list,
    # that model is promoted to the end of the final list. This process
    # continues until the input list is empty, or we do a full iteration
    # over the input models without promoting a model to the final list.
    # If we do a full iteration without a promotion, that means there are
    # circular dependencies in the list.
    model_list = []
    while model_dependencies:
        skipped = []
        changed = False
        while model_dependencies:
            model, deps = model_dependencies.pop()

            # If all of the models in the dependency list are either already
            # on the final model list, or not on the original serialization list,
            # then we've found another model with all it's dependencies satisfied.
            found = True
            for candidate in ((d not in models or d in model_list) for d in deps):
                if not candidate:
                    found = False
            if found:
                model_list.append(model)
                changed = True
            else:
                skipped.append((model, deps))
        if not changed:
            raise CommandError("Can't resolve dependencies for %s in serialized app list." %
                ', '.join('%s.%s' % (model._meta.app_label, model._meta.object_name)
                for model, deps in sorted(skipped, key=lambda obj: obj[0].__name__))
            )
        model_dependencies = skipped

    return model_list

BaseCommand.option_list was deprecated in Django 1.8 and has been removed in Django 1.10, so this code no longer works.

You also need to use collections.OrderedDict or something similar, as django.utils.datastructures.SortedDict was removed in Django 1.9.