[1.7.x] Fixed #22487: Optional rollback emulation for migrated apps

Conflicts:
	django/db/backends/creation.py
	django/test/runner.py
	docs/ref/settings.txt
	docs/topics/testing/advanced.txt

2 files changed, 29 insertions, 2 deletions

diff --git a/docs/ref/migration-operations.txt b/docs/ref/migration-operations.txt
index 40ef3849ac..95c9a65020 100644
--- a/docs/ref/migration-operations.txt
+++ b/docs/ref/migration-operations.txt
@@ -199,8 +199,9 @@ model::
         # We get the model from the versioned app registry;
         # if we directly import it, it'll be the wrong version
         Country = apps.get_model("myapp", "Country")
-        Country.objects.create(name="USA", code="us")
-        Country.objects.create(name="France", code="fr")
+        db_alias = schema_editor.connection.alias
+        Country.objects.create(name="USA", code="us", using=db_alias)
+        Country.objects.create(name="France", code="fr", using=db_alias)
 
     class Migration(migrations.Migration):
 
@@ -236,6 +237,14 @@ Oracle). This should be safe, but may cause a crash if you attempt to use
 the ``schema_editor`` provided on these backends; in this case, please
 set ``atomic=False``.
 
+.. warning::
+
+    RunPython does not magically alter the connection of the models for you;
+    any model methods you call will go to the default database unless you
+    give them the current database alias (available from
+    ``schema_editor.connection.alias``, where ``schema_editor`` is the second
+    argument to your function).
+
 SeparateDatabaseAndState
 ------------------------
 
diff --git a/docs/ref/settings.txt b/docs/ref/settings.txt
index c695131565..7f41939735 100644
--- a/docs/ref/settings.txt
+++ b/docs/ref/settings.txt
@@ -2116,6 +2116,24 @@ The name of the class to use for starting the test suite. See
     Previously the default ``TEST_RUNNER`` was
     ``django.test.simple.DjangoTestSuiteRunner``.
 
+.. setting:: TEST_NON_SERIALIZED_APPS
+
+TEST_NON_SERIALIZED_APPS
+------------------------
+
+Default: ``[]``
+
+In order to restore the database state between tests for TransactionTestCases
+and database backends without transactions, Django will :ref:`serialize the
+contents of all apps with migrations <test-case-serialized-rollback>` when it
+starts the test run so it can then reload from that copy before tests that
+need it.
+
+This slows down the startup time of the test runner; if you have apps that
+you know don't need this feature, you can add their full names in here (e.g.
+``django.contrib.contenttypes``) to exclude them from this serialization
+process.
+
 .. setting:: THOUSAND_SEPARATOR
 
 THOUSAND_SEPARATOR