Fixed #3163 -- Add a "Meta.managed" option to models.

This allows a model to be defined which is not subject to database table
creation and removal. Useful for models that sit over existing tables or
database views.

Thanks to Alexander Myodov, Wolfgang Kriesing and Ryan Kelly for the bulk of
this patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@10008 bcc190cf-cafb-0310-a4f2-bffc1f526a37

AUTHORS

@@ -297,6 +297,7 @@ answer newbie questions, and generally made Django that much better:
     James Murty
     msundstr
     Robert Myers <myer0052@gmail.com>
+    Alexander Myodov <alex@myodov.com>
     Nebojša Dorđević
     Doug Napoleone <doug@dougma.com>
     Gopal Narayanan <gopastro@gmail.com>

django/core/management/commands/syncdb.py

@@ -71,7 +71,7 @@ class Command(NoArgsCommand):
                     if refto in seen_models:
                         sql.extend(connection.creation.sql_for_pending_references(refto, self.style, pending_references))
                 sql.extend(connection.creation.sql_for_pending_references(model, self.style, pending_references))
-                if verbosity >= 1:
+                if verbosity >= 1 and sql:
                     print "Creating table %s" % model._meta.db_table
                 for statement in sql:
                     cursor.execute(statement)

django/db/backends/__init__.py

@@ -450,6 +450,8 @@ class BaseDatabaseIntrospection(object):
         tables = set()
         for app in models.get_apps():
             for model in models.get_models(app):
+                if not model._meta.managed:
+                    continue
                 tables.add(model._meta.db_table)
                 tables.update([f.m2m_db_table() for f in model._meta.local_many_to_many])
         if only_existing:
@@ -476,6 +478,8 @@ class BaseDatabaseIntrospection(object):
 
         for app in apps:
             for model in models.get_models(app):
+                if not model._meta.managed:
+                    continue
                 for f in model._meta.local_fields:
                     if isinstance(f, models.AutoField):
                         sequence_list.append({'table': model._meta.db_table, 'column': f.column})

django/db/backends/creation.py

@@ -33,6 +33,8 @@ class BaseDatabaseCreation(object):
         from django.db import models
 
         opts = model._meta
+        if not opts.managed:
+            return [], {}
         final_output = []
         table_output = []
         pending_references = {}
@@ -112,6 +114,8 @@ class BaseDatabaseCreation(object):
         "Returns any ALTER TABLE statements to add constraints after the fact."
         from django.db.backends.util import truncate_name
 
+        if not model._meta.managed:
+            return []
         qn = self.connection.ops.quote_name
         final_output = []
         opts = model._meta
@@ -225,6 +229,8 @@ class BaseDatabaseCreation(object):
 
     def sql_indexes_for_model(self, model, style):
         "Returns the CREATE INDEX SQL statements for a single model"
+        if not model._meta.managed:
+            return []
         output = []
         for f in model._meta.local_fields:
             output.extend(self.sql_indexes_for_field(model, f, style))
@@ -255,6 +261,8 @@ class BaseDatabaseCreation(object):
 
     def sql_destroy_model(self, model, references_to_delete, style):
         "Return the DROP TABLE and restraint dropping statements for a single model"
+        if not model._meta.managed:
+            return []
         # Drop the table now
         qn = self.connection.ops.quote_name
         output = ['%s %s;' % (style.SQL_KEYWORD('DROP TABLE'),
@@ -271,6 +279,8 @@ class BaseDatabaseCreation(object):
     def sql_remove_table_constraints(self, model, references_to_delete, style):
         from django.db.backends.util import truncate_name
 
+        if not model._meta.managed:
+            return []
         output = []
         qn = self.connection.ops.quote_name
         for rel_class, f in references_to_delete[model]:

django/db/models/options.py

@@ -21,7 +21,7 @@ get_verbose_name = lambda class_name: re.sub('(((?<=[a-z])[A-Z])|([A-Z](?![A-Z]|
 DEFAULT_NAMES = ('verbose_name', 'db_table', 'ordering',
                  'unique_together', 'permissions', 'get_latest_by',
                  'order_with_respect_to', 'app_label', 'db_tablespace',
-                 'abstract')
+                 'abstract', 'managed')
 
 class Options(object):
     def __init__(self, meta, app_label=None):
@@ -42,6 +42,7 @@ class Options(object):
         self.pk = None
         self.has_auto_field, self.auto_field = False, None
         self.abstract = False
+        self.managed = True
         self.parents = SortedDict()
         self.duplicate_targets = {}
         # Managers that have been inherited from abstract base classes. These

docs/ref/django-admin.txt

@@ -431,6 +431,8 @@ Currently supported:
 	* ``django`` for all ``*.py`` and ``*.html`` files (default)
 	* ``djangojs`` for ``*.js`` files
 
+.. _django-admin-reset:
+
 reset <appname appname ...>
 ---------------------------
 
@@ -634,6 +636,8 @@ This command is disabled when the ``--settings`` option to
 situations, either omit the ``--settings`` option or unset
 ``DJANGO_SETTINGS_MODULE``.
 
+.. _django-admin-syncdb:
+
 syncdb
 ------
 

docs/ref/models/options.txt

@@ -75,6 +75,30 @@ Example::
 
 See the docs for :meth:`~django.db.models.QuerySet.latest` for more.
 
+``managed``
+-----------------------
+
+.. attribute:: Options.managed
+
+.. versionadded:: 1.1
+
+If ``False``, no database table creation or deletion operations will be
+performed for this model. This is useful if the model represents an existing
+table or a database view that has been created by some other means.
+
+The default value is ``True``, meaning Django will create the appropriate
+database tables in :ref:`django-admin-syncdb` and remove them as part of a
+:ref:`reset <django-admin-reset>` management command.
+
+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.
+
+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.
+
 ``order_with_respect_to``
 -------------------------
 
@@ -181,3 +205,4 @@ The plural name for the object::
     verbose_name_plural = "stories"
 
 If this isn't given, Django will use :attr:`~Options.verbose_name` + ``"s"``.
+

tests/modeltests/unmanaged_models/__init__.py

@@ -0,0 +1,2 @@
+
+

tests/modeltests/unmanaged_models/models.py

@@ -0,0 +1,117 @@
+"""
+Models can have a ``managed`` attribute, which specifies whether the SQL code
+is generated for the table on various manage.py operations.
+"""
+
+from django.db import models
+
+#  All of these models are creatd in the database by Django.
+
+class A01(models.Model):
+    f_a = models.CharField(max_length=10, db_index=True)
+    f_b = models.IntegerField()
+
+    class Meta:
+        db_table = 'A01'
+
+    def __unicode__(self):
+        return self.f_a
+
+class B01(models.Model):
+    fk_a = models.ForeignKey(A01)
+    f_a = models.CharField(max_length=10, db_index=True)
+    f_b = models.IntegerField()
+
+    class Meta:
+        db_table = 'B01'
+        # 'managed' is True by default. This tests we can set it explicitly.
+        managed = True
+
+    def __unicode__(self):
+        return self.f_a
+
+class C01(models.Model):
+    mm_a = models.ManyToManyField(A01, db_table='D01')
+    f_a = models.CharField(max_length=10, db_index=True)
+    f_b = models.IntegerField()
+
+    class Meta:
+        db_table = 'C01'
+
+    def __unicode__(self):
+        return self.f_a
+
+# All of these models use the same tables as the previous set (they are shadows
+# of possibly a subset of the columns). There should be no creation errors,
+# since we have told Django they aren't managed by Django.
+
+class A02(models.Model):
+    f_a = models.CharField(max_length=10, db_index=True)
+
+    class Meta:
+        db_table = 'A01'
+        managed = False
+
+    def __unicode__(self):
+        return self.f_a
+
+class B02(models.Model):
+    class Meta:
+        db_table = 'B01'
+        managed = False
+
+    fk_a = models.ForeignKey(A02)
+    f_a = models.CharField(max_length=10, db_index=True)
+    f_b = models.IntegerField()
+
+    def __unicode__(self):
+        return self.f_a
+
+# To re-use the many-to-many intermediate table, we need to manually set up
+# things up.
+class C02(models.Model):
+    mm_a = models.ManyToManyField(A02, through="Intermediate")
+    f_a = models.CharField(max_length=10, db_index=True)
+    f_b = models.IntegerField()
+
+    class Meta:
+        db_table = 'C01'
+        managed = False
+
+    def __unicode__(self):
+        return self.f_a
+
+class Intermediate(models.Model):
+    a02 = models.ForeignKey(A02, db_column="a01_id")
+    c02 = models.ForeignKey(C02, db_column="c01_id")
+
+    class Meta:
+        db_table = 'D01'
+        managed = False
+
+__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
+whilst we're here to show that the second of models do refer to the tables from
+the first set.
+
+# Insert some data into one set of models.
+>>> a = A01.objects.create(f_a="foo", f_b=42)
+>>> _ = B01.objects.create(fk_a=a, f_a="fred", f_b=1729)
+>>> c = C01.objects.create(f_a="barney", f_b=1)
+>>> c.mm_a = [a]
+
+# ... and pull it out via the other set.
+>>> A02.objects.all()
+[<A02: foo>]
+>>> b = B02.objects.all()[0]
+>>> b
+<B02: fred>
+>>> b.fk_a
+<A02: foo>
+>>> C02.objects.filter(f_a=None)
+[]
+>>> C02.objects.filter(mm_a=a.id)
+[<C02: barney>]
+
+"""}