Fixed #10647: intermediary tables between two umanaged models are no longer created.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@10455 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/backends/creation.py

@@ -140,6 +140,7 @@ class BaseDatabaseCreation(object):
         "Return the CREATE TABLE statments for all the many-to-many tables defined on a model"
         output = []
         for f in model._meta.local_many_to_many:
+            if model._meta.managed or f.rel.to._meta.managed:
                 output.extend(self.sql_for_many_to_many_field(model, f, style))
         return output
 

docs/ref/models/options.txt

@@ -98,11 +98,16 @@ model handling are exactly the same as normal. This includes
        specify all the columns from the database table you are modeling when
        using unmanaged models.
 
-    2. If a model contains a :class:`~django.db.models.ManyToManyField` and
-       has ``managed=False``, the intermediate table for the many-to-many join
-       will also not be created. Should you require the intermediate table to
-       be created, set it up as an explicit model and use the
-       :attr:`ManyToManyField.through` attribute.
+    2. If a model with ``managed=False`` contains a
+       :class:`~django.db.models.ManyToManyField` that points to another
+       unmanaged model, then the intermediate table for the many-to-many join
+       will also not be created. However, a the intermediary table between one
+       managed and one unmanaged model *will* be created.
+       
+       If you need to change this default behavior, create the intermediary
+       table as an explicit model (with ``managed`` set as needed) and use the
+       :attr:`ManyToManyField.through` attribute to make the relation use your
+       custom model.
 
 For tests involving models with ``managed=False``, it's up to you to ensure
 the correct tables are created as part of the test setup.

tests/modeltests/unmanaged_models/models.py

@@ -89,6 +89,27 @@ class Intermediate(models.Model):
         db_table = 'D01'
         managed = False
 
+#
+# These next models test the creation (or not) of many to many join tables
+# between managed and unmanaged models. A join table between two unmanaged 
+# models shouldn't be automatically created (see #10647). 
+#
+class Unmanaged1(models.Model):    
+    class Meta:
+        managed = False
+
+# Unmanged with an m2m to unmanaged: the intermediary table won't be created.
+class Unmanaged2(models.Model):
+    mm = models.ManyToManyField(Unmanaged1)
+    
+    class Meta:
+        managed = False
+
+# Here's an unmanaged model with an m2m to a managed one; the intermediary
+# table *will* be created (unless given a custom `through` as for C02 above).
+class Managed1(models.Model):
+    mm = models.ManyToManyField(Unmanaged1)
+
 __test__ = {'API_TESTS':"""
 The main test here is that the all the models can be created without any
 database errors. We can also do some more simple insertion and lookup tests

tests/modeltests/unmanaged_models/tests.py

@@ -0,0 +1,22 @@
+from django.test import TestCase
+from django.db import connection
+from models import Unmanaged1, Unmanaged2, Managed1
+
+class ManyToManyUnmanagedTests(TestCase):
+            
+    def test_many_to_many_between_unmanaged(self):
+        """
+        The intermediary table between two unmanaged models should not be created.
+        """
+        table = Unmanaged2._meta.get_field('mm').m2m_db_table()
+        tables = connection.introspection.table_names()
+        self.assert_(table not in tables, "Table '%s' should not exist, but it does." % table)
+        
+    def test_many_to_many_between_unmanaged_and_managed(self):
+        """
+        An intermediary table between a managed and an unmanaged model should be created.
+        """
+        table = Managed1._meta.get_field('mm').m2m_db_table()
+        tables = connection.introspection.table_names()
+        self.assert_(table in tables, "Table '%s' does not exist." % table)
+