[soc2009/multidb] Added a using option to a Model's Meta class. This allows you to select the default database for a specific model, in addition to the global default

git-svn-id: http://code.djangoproject.com/svn/django/branches/soc2009/multidb@11135 bcc190cf-cafb-0310-a4f2-bffc1f526a37

TODO.txt

@@ -26,7 +26,4 @@ that need to be done.  I'm trying to be as granular as possible.
 
 4)  Wait on the merge of the m2m stuff.
 
-5)  Add the ``using`` Meta option.  Tests and docs(these are to be assumed at
-    each stage from here on out).
-
 6) Time permitting add support for a ``DatabaseManager``.

django/db/models/base.py

@@ -419,8 +419,7 @@ class Model(object):
         need for overrides of save() to pass around internal-only parameters
         ('raw', 'cls', and 'origin').
         """
-        if using is None:
+        using = using or self._meta.using or DEFAULT_DB_ALIAS
-            using = DEFAULT_DB_ALIAS
         connection = connections[using]
         assert not (force_insert and force_update)
         if cls is None:
@@ -563,8 +562,7 @@ class Model(object):
             parent_obj._collect_sub_objects(seen_objs)
 
     def delete(self, using=None):
-        if using is None:
+        using = using or self._meta.using or DEFAULT_DB_ALIAS
-            using = DEFAULT_DB_ALIAS
         connection = connections[using]
         assert self._get_pk_val() is not None, "%s object can't be deleted because its %s attribute is set to None." % (self._meta.object_name, self._meta.pk.attname)
 

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', 'managed', 'proxy')
+                 'abstract', 'managed', 'proxy', 'using')
 
 class Options(object):
     def __init__(self, meta, app_label=None):
@@ -47,6 +47,7 @@ class Options(object):
         self.proxy_for_model = None
         self.parents = SortedDict()
         self.duplicate_targets = {}
+        self.using = None
 
         # To handle various inheritance situations, we need to track where
         # managers came from (concrete or abstract base classes).
@@ -487,4 +488,3 @@ class Options(object):
         Returns the index of the primary key field in the self.fields list.
         """
         return self.fields.index(self.pk)
-

django/db/models/query.py

@@ -33,12 +33,14 @@ class QuerySet(object):
     """
     def __init__(self, model=None, query=None):
         self.model = model
-        connection = connections[DEFAULT_DB_ALIAS]
+        using = model._meta.using or DEFAULT_DB_ALIAS
+        connection = connections[using]
         self.query = query or sql.Query(self.model, connection)
         self._result_cache = None
         self._iter = None
         self._sticky_filter = False
-        self._using = connections.alias_for_connection(self.query.connection)
+        self._using = (query and
+            connections.alias_for_connection(self.query.connection) or using)
 
     ########################
     # PYTHON MAGIC METHODS #

docs/ref/models/options.txt

@@ -103,7 +103,7 @@ model handling are exactly the same as normal. This includes
        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
@@ -210,6 +210,17 @@ set of fields::
 
     unique_together = ("driver", "restaurant")
 
+``using``
+---------
+
+.. attribute:: Options.using
+
+The alias for the default database to be used for this model.  If this is not
+provided the default is ``'default'``.  If it is porvided it can be overidden
+at the ``QuerySet`` level with the ``using()`` method.
+
+.. versionadded:: TODO
+
 ``verbose_name``
 ----------------
 
@@ -232,4 +243,3 @@ The plural name for the object::
     verbose_name_plural = "stories"
 
 If this isn't given, Django will use :attr:`~Options.verbose_name` + ``"s"``.
-

docs/topics/db/multi-db.txt

@@ -25,6 +25,15 @@ thing to note is that your primary database should have the alias
 ``'default'``, and any additional databases you have can have whatever alias
 you choose.
 
+Selecting a Database for a ``Model``
+====================================
+
+In addition to the global default database for all models, it is possible to
+select a default database on a per-model level.  This is done using the
+``using`` option in a model's inner ``Meta`` class.  When provided this
+database becomes the default database for all lookups, saves, and deletes for
+this model.  It can be overiden on a per-query basis as described below.
+
 Selecting a Database for a ``QuerySet``
 =======================================
 

tests/regressiontests/multiple_database/models.py

@@ -1,4 +1,5 @@
-from django.db import models
+from django.conf import settings
+from django.db import models, DEFAULT_DB_ALIAS
 
 class Book(models.Model):
     title = models.CharField(max_length=100)
@@ -9,3 +10,15 @@ class Book(models.Model):
 
     class Meta:
         ordering = ('title',)
+
+if len(settings.DATABASES) > 1:
+    article_using = filter(lambda o: o != DEFAULT_DB_ALIAS, settings.DATABASES.keys())[0]
+    class Article(models.Model):
+        title = models.CharField(max_length=100)
+
+        def __unicode__(self):
+            return self.title
+
+        class Meta:
+            ordering = ('title',)
+            using = article_using

tests/regressiontests/multiple_database/tests.py

@@ -6,6 +6,13 @@ from django.test import TestCase
 
 from models import Book
 
+try:
+    # we only have these models if the user is using multi-db, it's safe the
+    # run the tests without them though.
+    from models import Article, article_using
+except ImportError:
+    pass
+
 class ConnectionHandlerTestCase(TestCase):
     def setUp(self):
         settings.DATABASES['__test_db'] = {
@@ -71,3 +78,18 @@ class QueryTestCase(TestCase):
 
             months = Book.objects.dates('published', 'month').using(db)
             self.assertEqual(sorted(o.month for o in months), [5, 12])
+
+if len(settings.DATABASES) > 1:
+    class MetaUsingTestCase(TestCase):
+        def test_meta_using_queries(self):
+            a = Article.objects.create(title="Django Rules!")
+            self.assertEqual(Article.objects.get(title="Django Rules!"), a)
+            for db in connections:
+                if db == article_using:
+                    self.assertEqual(Article.objects.using(db).get(title="Django Rules!"), a)
+                else:
+                    self.assertRaises(Article.DoesNotExist,
+                        lambda: Article.objects.using(db).get(title="Django Rules!"))
+            a.delete()
+            self.assertRaises(Article.DoesNotExist,
+                lambda: Article.objects.get(title="Django Rules!"))