From 8f20ca3111e40086c377f902f6171db831638d8b Mon Sep 17 00:00:00 2001
From: Yurchenko Sergey <urchenko88@gmail.com>
Date: Mon, 27 Jan 2020 22:24:32 +0300
Subject: [PATCH] command-to-delete-stale-records (#355)

* command-to-delete-stale-records
---
 constance/management/commands/constance.py | 31 ++++++++++++++++++++++
 docs/index.rst                             |  7 +++++
 tests/test_cli.py                          | 11 ++++++++
 3 files changed, 49 insertions(+)

diff --git a/constance/management/commands/constance.py b/constance/management/commands/constance.py
index 4d78769..c78ebf6 100644
--- a/constance/management/commands/constance.py
+++ b/constance/management/commands/constance.py
@@ -1,3 +1,5 @@
+from django.apps import apps
+from django.conf import settings
 from django.core.exceptions import ValidationError
 from django.core.management import BaseCommand, CommandError
 from django.utils.translation import ugettext as _
@@ -40,6 +42,13 @@ class Command(BaseCommand):
         # use nargs='+' so that we pass a list to MultiValueField (eg SplitDateTimeField)
         parser_set.add_argument('value', help='value to set', metavar='VALUE', nargs='+')
 
+        self._subparsers_add_parser(
+            subparsers,
+            'remove_stale_keys',
+            cmd=self,
+            help='delete all Constance keys and their values if they are not in settings.CONSTANCE_CONFIG (stale keys)',
+        )
+
 
     def _subparsers_add_parser(self, subparsers, name, **kwargs):
         # API in Django >= 2.1 changed and removed cmd parameter from add_parser
@@ -71,3 +80,25 @@ class Command(BaseCommand):
         elif command == 'list':
             for k, v in get_values().items():
                 self.stdout.write("{}\t{}".format(k, v), ending="\n")
+
+        elif command == 'remove_stale_keys':
+            try:
+                Constance = apps.get_model('database.Constance')
+            except LookupError:
+                Constance = None
+
+            if Constance:
+                actual_keys = settings.CONSTANCE_CONFIG.keys()
+
+                stale_records = Constance.objects.exclude(key__in=actual_keys)
+                if stale_records:
+                    self.stdout.write("The following record will be deleted:", ending="\n")
+                else:
+                    self.stdout.write("There are no stale records in database.", ending="\n")
+
+                for stale_record in stale_records:
+                    self.stdout.write("{}\t{}".format(stale_record.key, stale_record.value), ending="\n")
+
+                stale_records.delete()
+            else:
+                self.stdout.write("Database backend is not set. Nothing is deleted", ending="\n")
diff --git a/docs/index.rst b/docs/index.rst
index 818f24b..b14340d 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -326,6 +326,13 @@ This doesn't work::
    ./manage.py constance set DATETIME_VALUE '2011-09-24 12:30:25'
    CommandError: Enter a list of values.
 
+
+remove_stale_keys - delete all stale records in database::
+
+    $ ./manage.py constance remove_stale_keys
+
+Record is considered stale if it exists in database but absent in config
+
 Editing
 -------
 
diff --git a/tests/test_cli.py b/tests/test_cli.py
index ec00239..1a17187 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -1,6 +1,7 @@
 from datetime import datetime
 from textwrap import dedent
 
+from django.apps import apps
 from django.conf import settings
 from django.core.management import call_command, CommandError
 from django.test import TransactionTestCase
@@ -71,3 +72,13 @@ class CliTestCase(TransactionTestCase):
     def test_set_invalid_multi_value(self):
         self.assertRaisesMessage(CommandError, "Enter a list of values.",
                                  call_command, 'constance', 'set', 'DATETIME_VALUE', '2011-09-24 12:30:25')
+
+    def test_delete_stale_records(self):
+        Constance = apps.get_model('database.Constance')
+
+        initial_count = Constance.objects.count()
+
+        Constance.objects.create(key='STALE_KEY', value=None)
+        call_command('constance', 'remove_stale_keys', stdout=self.out)
+
+        self.assertEqual(Constance.objects.count(), initial_count)