topological sorting issue with self-ref m2o

[Mike Bayer]

from sqlalchemy.ext.declarative import declarative_base, declared_attr
from sqlalchemy import *
from sqlalchemy.orm import relationship, Session, backref

Base = declarative_base()

class Group(Base):
    __tablename__ = 'group'
    id = Column(Integer, primary_key=True)
    parent_id = Column(Integer, ForeignKey('group.id'))
    name = Column(Unicode, nullable=False)
    children = relationship("Group",
                            backref=backref("parent", 
                                    # fixes
                                    #active_history=True,
                                    remote_side="Group.id"))

    def __init__(self, name):
        self.name = name

e = create_engine("sqlite://", echo=True)
Base.metadata.create_all(e)
s = Session(e)

g1 = Group(name="g1")
g1.parent = Group(name='g2')
s.add(g1)
s.commit()
s.close()

g1 = s.query(Group).filter_by(name='g1').one()
g1.parent = None
s.commit()

assert g1.parent is None

without active history, g1.parent gets PASSIVE_NO_RESULT in committed state. When the cycle resolution for the self-referential .parent gets figured out, ScalarObjectAttributeImpl.get_all_pending skips entries that are PASSIVE_NO_RESULT.

diff -r 6de2aa03bdfd3fd40b36bc4d052f6f1f10f10fe8 lib/sqlalchemy/orm/attributes.py
--- a/lib/sqlalchemy/orm/attributes.py  Fri Apr 27 15:21:02 2012 -0700
+++ b/lib/sqlalchemy/orm/attributes.py  Wed May 02 14:56:05 2012 -0400
@@ -657,7 +657,9 @@

             if self.key in state.committed_state:
                 original = state.committed_state[self.key](self.key)
-                if original not in (NEVER_SET, PASSIVE_NO_RESULT, None) and \
+                if original is PASSIVE_NO_RESULT:
+                    ret.append((original, original))
+                elif original not in (NEVER_SET, None) and \
                     original is not current:

                     ret.append((instance_state(original), original))

not sure if this is for 0.7.7 or not, as this has been broken like this since at least the new uow in 0.6. need to determine potential backwards incompatibilities.

[Mike Bayer]

another way to do it:

diff -r 6de2aa03bdfd3fd40b36bc4d052f6f1f10f10fe8 lib/sqlalchemy/orm/attributes.py
--- a/lib/sqlalchemy/orm/attributes.py  Fri Apr 27 15:21:02 2012 -0700
+++ b/lib/sqlalchemy/orm/attributes.py  Wed May 02 15:00:14 2012 -0400
@@ -653,7 +653,7 @@
             if current is not None:
                 ret = [current)]((instance_state(current),)
             else:
-                ret = [               ret = [(None, None)](]
+)

             if self.key in state.committed_state:
                 original = state.committed_state[self.key](self.key)

[Mike Bayer]

will go to 0.7. 0.6 is doing this differently, and prior to d94c1d1ac30821572c7c5cf864825d5f552b81b3 there are additional bugs in 0.6 that prevent this from being a simple backport.

[Mike Bayer]

25b6e811e692d20495ea6bed93552a22a28f9d92 3757034d2de03f23dabb9456d773e34b8b09edb0

[Mike Bayer]

Removing milestone: 0.7.7 (automated comment)