Fixed #27858 -- Prevented read-only management commands from creating the django_migrations table.

MigrationRecorder now assumes that if the django_migrations table
doesn't exist, then no migrations are applied.

Reverted documentation change from refs #23808.

3 files changed, 15 insertions, 9 deletions

diff --git a/django/core/management/base.py b/django/core/management/base.py
index bfc6811e28..41b6b0fa91 100644
--- a/django/core/management/base.py
+++ b/django/core/management/base.py
@@ -12,7 +12,6 @@ from django.core import checks
 from django.core.exceptions import ImproperlyConfigured
 from django.core.management.color import color_style, no_style
 from django.db import DEFAULT_DB_ALIAS, connections
-from django.db.migrations.exceptions import MigrationSchemaMissing
 
 
 class CommandError(Exception):
@@ -429,11 +428,6 @@ class BaseCommand:
         except ImproperlyConfigured:
             # No databases are configured (or the dummy one)
             return
-        except MigrationSchemaMissing:
-            self.stdout.write(self.style.NOTICE(
-                "\nNot checking migrations as it is not possible to access/create the django_migrations table."
-            ))
-            return
 
         plan = executor.migration_plan(executor.loader.graph.leaf_nodes())
         if plan:
diff --git a/django/db/migrations/executor.py b/django/db/migrations/executor.py
index ab412fe6d1..ea7bc70db3 100644
--- a/django/db/migrations/executor.py
+++ b/django/db/migrations/executor.py
@@ -86,6 +86,10 @@ class MigrationExecutor:
         Django first needs to create all project states before a migration is
         (un)applied and in a second step run all the database operations.
         """
+        # The django_migrations table must be present to record applied
+        # migrations.
+        self.recorder.ensure_schema()
+
         if plan is None:
             plan = self.migration_plan(targets)
         # Create the forwards plan Django would follow on an empty database
diff --git a/django/db/migrations/recorder.py b/django/db/migrations/recorder.py
index dcc27d525c..2a3ff8bb99 100644
--- a/django/db/migrations/recorder.py
+++ b/django/db/migrations/recorder.py
@@ -39,11 +39,15 @@ class MigrationRecorder:
     def migration_qs(self):
         return self.Migration.objects.using(self.connection.alias)
 
+    def has_table(self):
+        """Return True if the django_migrations table exists."""
+        return self.Migration._meta.db_table in self.connection.introspection.table_names(self.connection.cursor())
+
     def ensure_schema(self):
         """Ensure the table exists and has the correct schema."""
         # If the table's there, that's fine - we've never changed its schema
         # in the codebase.
-        if self.Migration._meta.db_table in self.connection.introspection.table_names(self.connection.cursor()):
+        if self.has_table():
             return
         # Make the table
         try:
@@ -54,8 +58,12 @@ class MigrationRecorder:
 
     def applied_migrations(self):
         """Return a set of (app, name) of applied migrations."""
-        self.ensure_schema()
-        return {tuple(x) for x in self.migration_qs.values_list("app", "name")}
+        if self.has_table():
+            return {tuple(x) for x in self.migration_qs.values_list('app', 'name')}
+        else:
+            # If the django_migrations table doesn't eixst, then no migrations
+            # are applied.
+            return set()
 
     def record_applied(self, app, name):
         """Record that a migration was applied."""