[soc2009/multidb] Correctly handle pickling of Query objects, restoring them to the correct database.

git-svn-id: http://code.djangoproject.com/svn/django/branches/soc2009/multidb@11274 bcc190cf-cafb-0310-a4f2-bffc1f526a37

TODO.txt

@@ -22,4 +22,4 @@ that need to be done.  I'm trying to be as granular as possible.
 
 6)  Generate SQL, instead of an error for nesting on different DBs.
 
-7) Time permitting add support for a ``DatabaseManager``.
+7)  Time permitting add support for a ``DatabaseManager``.

django/db/backends/__init__.py

@@ -33,6 +33,12 @@ class BaseDatabaseWrapper(local):
         self.queries = []
         self.settings_dict = settings_dict
 
+    def __eq__(self, other):
+        return self.settings_dict == other.settings_dict
+
+    def __ne__(self, other):
+        return not self == other
+
     def _commit(self):
         if self.connection is not None:
             return self.connection.commit()

django/db/models/query.py

@@ -750,7 +750,7 @@ class QuerySet(object):
         Returns the internal query's SQL and parameters (as a tuple).
         """
         obj = self.values("pk")
-        if connection.settings_dict == obj.query.connection.settings_dict:
+        if connection == obj.query.connection:
             return obj.query.as_nested_sql()
         raise ValueError("Can't do subqueries with queries on different DBs.")
 
@@ -879,7 +879,7 @@ class ValuesQuerySet(QuerySet):
                     % self.__class__.__name__)
 
         obj = self._clone()
-        if connection.settings_dict == obj.query.connection.settings_dict:
+        if connection == obj.query.connection:
             return obj.query.as_nested_sql()
         raise ValueError("Can't do subqueries with queries on different DBs.")
 

django/db/models/sql/query.py

@@ -13,7 +13,7 @@ from django.utils.tree import Node
 from django.utils.datastructures import SortedDict
 from django.utils.encoding import force_unicode
 from django.db.backends.util import truncate_name
-from django.db import connection
+from django.db import connection, connections
 from django.db.models import signals
 from django.db.models.fields import FieldDoesNotExist
 from django.db.models.query_utils import select_related_descend
@@ -126,6 +126,7 @@ class BaseQuery(object):
         obj_dict['related_select_fields'] = []
         obj_dict['related_select_cols'] = []
         del obj_dict['connection']
+        obj_dict['connection_settings'] = self.connection.settings_dict
 
         # Fields can't be pickled, so if a field list has been
         # specified, we pickle the list of field names instead.
@@ -147,10 +148,8 @@ class BaseQuery(object):
         ]
 
         self.__dict__.update(obj_dict)
-        # XXX: Need a better solution for this when multi-db stuff is
-        # supported. It's the only class-reference to the module-level
-        # connection variable.
-        self.connection = connection
+        self.connection = connections[connections.alias_for_settings(
+            obj_dict['connection_settings'])]
 
     def get_meta(self):
         """

django/db/utils.py

@@ -81,8 +81,14 @@ class ConnectionHandler(object):
         """
         Returns the alias for the given connection object.
         """
+        return self.alias_for_settings(connection.settings_dict)
+
+    def alias_for_settings(self, settings_dict):
+        """
+        Returns the alias for the given settings dictionary.
+        """
         for alias in self:
             conn_settings = self.databases[alias]
-            if conn_settings == connection.settings_dict:
+            if conn_settings == settings_dict:
                 return alias
         return None

tests/regressiontests/multiple_database/tests.py

@@ -1,4 +1,5 @@
 import datetime
+import pickle
 
 from django.conf import settings
 from django.db import connections
@@ -79,6 +80,15 @@ class QueryTestCase(TestCase):
             months = Book.objects.dates('published', 'month').using(db)
             self.assertEqual(sorted(o.month for o in months), [5, 12])
 
+class PickleQuerySetTestCase(TestCase):
+    def test_pickling(self):
+        for db in connections:
+            qs = Book.objects.all()
+            self.assertEqual(qs.query.connection,
+                pickle.loads(pickle.dumps(qs)).query.connection)
+            self.assertEqual(qs._using, pickle.loads(pickle.dumps(qs))._using)
+
+
 if len(settings.DATABASES) > 1:
     class MetaUsingTestCase(TestCase):
         def test_meta_using_queries(self):