def select_for_update(self, dbclass, key):
"""
This method works like L{select_by_primary_key} above, except that it
doesn't select anything but returns a dummy object (an empty dbobj)
that will allow setting attributes, yielding proper UPDATE statements.
Note that supplying a primary key that does not exist will go
unnoticed: The UPDATE statements won't create an error, they just
won't affect any rows.
This method is primarily ment for transaction based (i.e. www)
applications.
"""
if type(key) != TupleType: key = ( key, )
primary_key = keys.primary_key(dbclass)
if len(key) != len(primary_key.key_attributes):
msg = "The primary key for %s must have %i elements." % \
( repr(dbclass), len(primary_key.key_attributes), )
raise IllegalPrimaryKey(msg)
info = stupid_dict()
for property, value in zip(primary_key.attributes(), key):
info[property.column] = value
return dbclass.__from_result__(self, info)
def rollback(self):
"""
Undo the changes you made to the database since the last commit()
"""
self._updates = stupid_dict()
db = getattr(self._conn, "db", None)
if db is not None:
db.rollback()
