Fixed #16330 -- added --pks option in dumpdata command

Thanks to guettli for the initial ticket and patch, with additional work
from mehmetakyuz and Kevin Brolly.

django/core/management/commands/dumpdata.py

@@ -21,6 +21,8 @@ class Command(BaseCommand):
             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', action='append', default=[],
+            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."),
     )
     help = ("Output the contents of the database as a fixture of the given "
             "format (using each model's default manager unless --all is "
@@ -37,6 +39,12 @@ class Command(BaseCommand):
         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')
+
+        if pks:
+            primary_keys = pks.split(',')
+        else:
+            primary_keys = False
 
         excluded_apps = set()
         excluded_models = set()
@@ -55,8 +63,12 @@ class Command(BaseCommand):
                     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:
@@ -77,6 +89,8 @@ class Command(BaseCommand):
                     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:
@@ -107,8 +121,11 @@ class Command(BaseCommand):
                         objects = model._base_manager
                     else:
                         objects = model._default_manager
-                    for obj in objects.using(using).\
+
-                            order_by(model._meta.pk.name).iterator():
+                    queryset = objects.using(using).order_by(model._meta.pk.name)
+                    if primary_keys:
+                        queryset = queryset.filter(pk__in=primary_keys)
+                    for obj in queryset.iterator():
                         yield obj
 
         try:

docs/ref/django-admin.txt

@@ -227,6 +227,15 @@ a natural key definition. If you are dumping ``contrib.auth`` ``Permission``
 objects or ``contrib.contenttypes`` ``ContentType`` objects, you should
 probably be using this flag.
 
+.. versionadded:: 1.6
+
+.. django-admin-option:: --pks
+
+By default, ``dumpdata`` will output all the records of the model, but
+you can use the ``--pks`` option to specify a comma seperated list of
+primary keys on which to filter.  This is only available when dumping
+one model.
+
 flush
 -----
 

docs/releases/1.6.txt

@@ -249,6 +249,10 @@ Minor features
   and :func:`~django.contrib.auth.views.password_change`, you can now pass
   URL names and they will be resolved.
 
+* The ``dumpdata`` manage.py command now has a --pks option which will
+  allow users to specify the primary keys of objects they want to dump.
+  This option can only be used with one model.
+
 Backwards incompatible changes in 1.6
 =====================================
 

tests/fixtures/tests.py

@@ -27,14 +27,15 @@ class TestCaseFixtureLoadingTests(TestCase):
 class DumpDataAssertMixin(object):
 
     def _dumpdata_assert(self, args, output, format='json', natural_keys=False,
-                         use_base_manager=False, exclude_list=[]):
+                         use_base_manager=False, exclude_list=[], primary_keys=[]):
         new_io = six.StringIO()
         management.call_command('dumpdata', *args, **{'format': format,
                                                       'stdout': new_io,
                                                       'stderr': new_io,
                                                       'use_natural_keys': natural_keys,
                                                       'use_base_manager': use_base_manager,
-                                                      'exclude': exclude_list})
+                                                      'exclude': exclude_list,
+                                                      'primary_keys': primary_keys})
         command_output = new_io.getvalue().strip()
         if format == "json":
             self.assertJSONEqual(command_output, output)
@@ -223,6 +224,45 @@ class FixtureLoadingTests(DumpDataAssertMixin, TestCase):
         # even those normally filtered by the manager
         self._dumpdata_assert(['fixtures.Spy'], '[{"pk": %d, "model": "fixtures.spy", "fields": {"cover_blown": true}}, {"pk": %d, "model": "fixtures.spy", "fields": {"cover_blown": false}}]' % (spy2.pk, spy1.pk), use_base_manager=True)
 
+    def test_dumpdata_with_pks(self):
+        management.call_command('loaddata', 'fixture1.json', verbosity=0, commit=False)
+        management.call_command('loaddata', 'fixture2.json', verbosity=0, commit=False)
+        self._dumpdata_assert(
+            ['fixtures.Article'],
+            '[{"pk": 2, "model": "fixtures.article", "fields": {"headline": "Poker has no place on ESPN", "pub_date": "2006-06-16T12:00:00"}}, {"pk": 3, "model": "fixtures.article", "fields": {"headline": "Copyright is fine the way it is", "pub_date": "2006-06-16T14:00:00"}}]',
+            primary_keys='2,3'
+        )
+
+        self._dumpdata_assert(
+            ['fixtures.Article'],
+            '[{"pk": 2, "model": "fixtures.article", "fields": {"headline": "Poker has no place on ESPN", "pub_date": "2006-06-16T12:00:00"}}]',
+            primary_keys='2'
+        )
+
+        with six.assertRaisesRegex(self, management.CommandError,
+                "You can only use --pks option with one model"):
+            self._dumpdata_assert(
+                ['fixtures'],
+                '[{"pk": 2, "model": "fixtures.article", "fields": {"headline": "Poker has no place on ESPN", "pub_date": "2006-06-16T12:00:00"}}, {"pk": 3, "model": "fixtures.article", "fields": {"headline": "Copyright is fine the way it is", "pub_date": "2006-06-16T14:00:00"}}]',
+                primary_keys='2,3'
+            )
+
+        with six.assertRaisesRegex(self, management.CommandError,
+                "You can only use --pks option with one model"):
+            self._dumpdata_assert(
+                '',
+                '[{"pk": 2, "model": "fixtures.article", "fields": {"headline": "Poker has no place on ESPN", "pub_date": "2006-06-16T12:00:00"}}, {"pk": 3, "model": "fixtures.article", "fields": {"headline": "Copyright is fine the way it is", "pub_date": "2006-06-16T14:00:00"}}]',
+                primary_keys='2,3'
+            )
+
+        with six.assertRaisesRegex(self, management.CommandError,
+                "You can only use --pks option with one model"):
+            self._dumpdata_assert(
+                ['fixtures.Article', 'fixtures.category'],
+                '[{"pk": 2, "model": "fixtures.article", "fields": {"headline": "Poker has no place on ESPN", "pub_date": "2006-06-16T12:00:00"}}, {"pk": 3, "model": "fixtures.article", "fields": {"headline": "Copyright is fine the way it is", "pub_date": "2006-06-16T14:00:00"}}]',
+                primary_keys='2,3'
+            )
+
     def test_compress_format_loading(self):
         # Load fixture 4 (compressed), using format specification
         management.call_command('loaddata', 'fixture4.json', verbosity=0, commit=False)