I'm not sure why. But when I do a delete/sql alchemy seems to be
running the save/delete operation twice. Could this be related to a
circular dependency in UOW that is undetected?? When deleting this is
causing the following error because the database delete is done twice:
sqlalchemy.exceptions.ConcurrentModificationError: Updated rowcount 0
does not match number of objects updated
To fix this I added the following, but it is a serious hack, and
probably needs to be addressed in the unit of work code, but I'm not
sure where to look. Code below. I am on 0.3.5, however I tested
against 0.3.6 as well and this bug appears to be present there as
well.
in orm.unitofwork.UnitOfWork
def _remove_deleted(self, obj):
if hasattr(obj, "_instance_key"):
# ADDED
# ignore key errors if the item has already been
deleted
try :
del self.identity_map[obj._instance_key]
except KeyError:
pass
try:
self.deleted.remove(obj)
except KeyError:
pass
try:
self.new.remove(obj)
except KeyError:
pass
in orm.mapper.Mapper
def delete_obj(self, objects, uowtransaction):
"""issue DELETE statements for a list of objects.
this is called within the context of a UOWTransaction during a
flush operation."""
if self.__should_log_debug:
self.__log_debug("delete_obj() start")
connection = uowtransaction.transaction.connection(self)
[self.extension.before_delete(self, connection, obj) for obj
in objects]
deleted_objects = util.Set()
for table in self.tables.sort(reverse=True):
if not self._has_pks(table):
continue
delete = []
for obj in objects:
# ADDED
# 4/17/07
# this prevents items from being deleted twice
if hasattr(obj, '_has_been_deleted_') :
continue
params = {}
if not hasattr(obj, "_instance_key"):
continue
else:
delete.append(params)
for col in self.pks_by_table[table]:
params[col.key] = self.get_attr_by_column(obj,
col)
if self.version_id_col is not None:
params[self.version_id_col.key] =
self.get_attr_by_column(obj, self.version_id_col)
deleted_objects.add(obj)
if len(delete):
def comparator(a, b):
for col in self.pks_by_table[table]:
x = cmp(a[col.key],b[col.key])
if x != 0:
return x
return 0
delete.sort(comparator)
clause = sql.and_()
for col in self.pks_by_table[table]:
clause.clauses.append(col ==
sql.bindparam(col.key, type=col.type))
if self.version_id_col is not None:
clause.clauses.append(self.version_id_col ==
sql.bindparam(self.version_id_col.key, type=self.version_id_col.type))
statement = table.delete(clause)
c = connection.execute(statement, delete)
if c.supports_sane_rowcount() and c.rowcount !=
len(delete):
raise
exceptions.ConcurrentModificationError("Updated rowcount %d does not
match number of objects updated %d" % (c.cursor.rowcount,
len(delete)))
# ADDED
# this prevents items from being deleted twice
for obj in deleted_objects :
obj._has_been_deleted_ = True
[self.extension.after_delete(self, connection, obj) for obj in
deleted_objects]
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