diff options
Diffstat (limited to 'django/db/models/sql')
| -rw-r--r-- | django/db/models/sql/subqueries.py | 23 |
1 files changed, 20 insertions, 3 deletions
diff --git a/django/db/models/sql/subqueries.py b/django/db/models/sql/subqueries.py index 1f9a13ecdc..7385cd00e1 100644 --- a/django/db/models/sql/subqueries.py +++ b/django/db/models/sql/subqueries.py @@ -159,20 +159,37 @@ class UpdateQuery(Query): # from other tables. query = self.clone(klass=Query) query.bump_prefix() - query.select = [] query.extra_select = {} - query.add_fields([query.model._meta.pk.name]) + first_table = query.tables[0] + if query.alias_refcount[first_table] == 1: + # We can remove one table from the inner query. + query.unref_alias(first_table) + for i in xrange(1, len(query.tables)): + table = query.tables[i] + if query.alias_refcount[table]: + break + join_info = query.alias_map[table] + query.select = [(join_info[RHS_ALIAS], join_info[RHS_JOIN_COL])] + must_pre_select = False + else: + query.select = [] + query.add_fields([query.model._meta.pk.name]) + must_pre_select = not self.connection.features.update_can_self_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() - if self.related_updates: + if self.related_updates or must_pre_select: + # Either we're using the idents in multiple update queries (so + # don't want them to change), or the db backend doesn't support + # selecting from the updating table (e.g. MySQL). idents = [] for rows in query.execute_sql(MULTI): idents.extend([r[0] for r in rows]) self.add_filter(('pk__in', idents)) 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:]: self.alias_refcount[alias] = 0 |