queryset-refactor: Querysets no longer need to be customised per-backend.

Instead, it's the Query class that is backend-dependent. So make that explicit
in the code (code should refer to sql.Query and they will always get the right
backend-specific class).

This also fixes the main part of #6956, in that the various subclasses of Query
automatically use any custom Query class.

Fixed #6956.


git-svn-id: http://code.djangoproject.com/svn/django/branches/queryset-refactor@7426 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/query.py

@@ -16,7 +16,7 @@ ITER_CHUNK_SIZE = CHUNK_SIZE
 # Pull into this namespace for backwards compatibility
 EmptyResultSet = sql.EmptyResultSet
 
-class _QuerySet(object):
+class QuerySet(object):
     "Represents a lazy database lookup for a set of objects"
     def __init__(self, model=None, query=None):
         self.model = model
@@ -478,12 +478,6 @@ class _QuerySet(object):
             raise TypeError("Cannot merge querysets of different types ('%s' and '%s'."
                     % (self.__class__.__name__, other.__class__.__name__))
 
-# Use the backend's QuerySet class if it defines one. Otherwise, use _QuerySet.
-if connection.features.uses_custom_queryset:
-    QuerySet = connection.ops.query_set_class(_QuerySet)
-else:
-    QuerySet = _QuerySet
-
 class ValuesQuerySet(QuerySet):
     def __init__(self, *args, **kwargs):
         super(ValuesQuerySet, self).__init__(*args, **kwargs)

django/db/models/sql/query.py

@@ -13,6 +13,7 @@ from copy import deepcopy
 from django.utils.tree import Node
 from django.utils.datastructures import SortedDict
 from django.dispatch import dispatcher
+from django.db import connection
 from django.db.models import signals
 from django.db.models.sql.where import WhereNode, EverythingNode, AND, OR
 from django.db.models.sql.datastructures import Count
@@ -1371,6 +1372,11 @@ class Query(object):
         return iter((lambda: cursor.fetchmany(GET_ITERATOR_CHUNK_SIZE)),
                 self.connection.features.empty_fetchmany_value)
 
+# Use the backend's custom Query class if it defines one. Otherwise, use the
+# default.
+if connection.features.uses_custom_query_class:
+    Query = connection.ops.query_class(Query)
+
 def get_order_dir(field, default='ASC'):
     """
     Returns the field name and direction for an order specification. For