Ticket #2705: for_update_7477.patch

django/db/models/sql/query.py

@@ -67 +67 @@
         self.order_by = []
         self.low_mark, self.high_mark = 0, None  # Used for offset/limit
         self.distinct = False
+        self.select_for_update = False
         self.select_related = False
         self.related_select_cols = []
 
@@ -155 +156 @@
         obj.order_by = self.order_by[:]
         obj.low_mark, obj.high_mark = self.low_mark, self.high_mark
         obj.distinct = self.distinct
+        obj.select_for_update = self.select_for_update
         obj.select_related = self.select_related
         obj.related_select_cols = []
         obj.max_depth = self.max_depth
@@ -193 +195 @@
         obj = self.clone()
         obj.clear_ordering(True)
         obj.clear_limits()
+        obj.select_for_update = False
         obj.select_related = False
         obj.related_select_cols = []
         obj.related_select_fields = []
@@ -272 +275 @@
                         result.append('LIMIT %d' % val)
                 result.append('OFFSET %d' % self.low_mark)
 
+        if self.select_for_update:
+            result.append("%s" % self.connection.ops.for_update_sql())
+
         params.extend(self.extra_params)
         return ' '.join(result), tuple(params)
 

django/db/models/manager.py

@@ -108 +108 @@
     def order_by(self, *args, **kwargs):
         return self.get_query_set().order_by(*args, **kwargs)
 
+    def select_for_update(self, *args, **kwargs): 
+        return self.get_query_set().select_for_update(*args, **kwargs)
+        
     def select_related(self, *args, **kwargs):
         return self.get_query_set().select_related(*args, **kwargs)
 

django/db/models/query.py

@@ -256 +256 @@
         del_query = self._clone()
 
         # Disable non-supported fields.
+        del_query.query.select_for_update = False
         del_query.query.select_related = False
         del_query.query.clear_ordering()
 
@@ -390 +391 @@
         else:
             return self._filter_or_exclude(None, **filter_obj)
 
+    def select_for_update(self):
+        """
+        Returns a new QuerySet instance that will select objects with a
+        FOR UPDATE lock.
+        """
+        obj = self._clone()
+        obj.query.select_for_update = True
+        return obj
+
     def select_related(self, *fields, **kwargs):
         """
         Returns a new QuerySet instance that will select related objects. If

django/db/backends/sqlite3/base.py

@@ -52 +52 @@
         # function django_date_trunc that's registered in connect().
         return 'django_date_trunc("%s", %s)' % (lookup_type.lower(), field_name)
 
+    def for_update_sql():
+        # sqlite does not support FOR UPDATE
+        return ''
+
     def drop_foreignkey_sql(self):
         return ""
 
@@ -171 +175 @@
         return bool(re.search(re_pattern, re_string))
     except:
         return False
+

django/db/backends/__init__.py

@@ -159 +159 @@
         """
         return cursor.lastrowid
 
+    def for_update_sql(self):
+        """
+        Return FOR UPDATE SQL clause to lock row for update
+        """
+        return 'FOR UPDATE' 
+
     def limit_offset_sql(self, limit, offset=None):
         """
         Returns a LIMIT/OFFSET SQL clause, given a limit and optional offset.