Changeset 7496

Timestamp:

04/28/08 06:51:52 (2 months ago)

Author:

mtredinnick

Message:

Made some types of nested update queries very slightly more efficient at the
database level. Also worked around the fact that MySQL (and maybe other
backends we don't know about) cannot select from the table they're updating.

Fixed #7095.

Files:

• django/trunk/django/db/backends/__init__.py (modified) (1 diff)
• django/trunk/django/db/backends/mysql/base.py (modified) (1 diff)
• django/trunk/django/db/backends/mysql_old/base.py (modified) (1 diff)
• django/trunk/django/db/models/sql/subqueries.py (modified) (2 diffs)

django/trunk/django/db/backends/__init__.py

@@ -52 +52 @@
-    uses_custom_query_class = False
-    empty_fetchmany_value = []
+    update_can_self_select = True
-
-class BaseDatabaseOperations(object):

django/trunk/django/db/backends/mysql/base.py

@@ -64 +64 @@
-    inline_fk_references = False
-    empty_fetchmany_value = ()
+    update_can_self_select = False
-
-class DatabaseOperations(BaseDatabaseOperations):

django/trunk/django/db/backends/mysql_old/base.py

@@ -68 +68 @@
-    inline_fk_references = False
-    empty_fetchmany_value = ()
+    update_can_self_select = False
-
-class DatabaseOperations(BaseDatabaseOperations):

django/trunk/django/db/models/sql/subqueries.py

@@ -160 +160 @@
-        query = self.clone(klass=Query)
-        query.bump_prefix()
-        query.select = []
-        query.extra_select = {}
-
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
-
-        # Now we adjust the current query: reset the where clause and get rid
-        # of all the tables we don't need (since they're in the sub-select).
-        self.where = self.where_class()
-
+
+
+
+
-            idents = []
-            for rows in query.execute_sql(MULTI):
@@ -174 +190 @@
-            self.related_ids = idents
-        else:
+            # The fast path. Filters and updates in one query.
-            self.add_filter(('pk__in', query))
-        for alias in self.tables[1:]: