Using the default_engine, instead of defining an engine causes a 'No connection established' error when defining a relation in a mapper

(original reporter: creiht) I have the following code block:

tiles = Table('tiles',
        Column('id', Integer, primary_key = True),
        Column('width', Integer),
        Column('height', Integer),
        Column('image', Binary),
        )

tags = Table('tags',
        Column('id', Integer, primary_key = True),
        Column('name', String(50)),
        Column('description', String),
        )

tiles_tags = Table('tiles_tags',
        Column('id', Integer, primary_key = True),
        Column('tiles_id', Integer, ForeignKey('tiles.id')),
        Column('tags_id', Integer, ForeignKey('tags.id')),
        )

class Tile(object):
    pass

class Tag(object):
    pass

assign_mapper(Tag, tags)
assign_mapper(Tile, tiles, properties = {
        'tags' : relation(Tag.mapper, tiles_tags, lazy=False,
            backref=backref('tiles', lazy=False, private=True)
            )
        }
    )

I get the following traceback:

exceptions.AttributeError                            Traceback (most recent call last)

/workspace/personal/sprite/<console>

/workspace/personal/sprite/spriteDB.py 
     41 assign_mapper(Tile, tiles, properties = {
     42         'tags' : relation(Tag.mapper, tiles_tags, lazy=False,
---> 43             backref=backref('tiles', lazy=False, private=True)
     44             )
     45         }

/opt/local/lib/python2.4/site-packages/SQLAlchemy-0.1.5-py2.4.egg/sqlalchemy/mapping/__init__.py in assign_mapper(class_, *args, **params)
    103                  setattr(self, key, value)
    104         class_.__init__ = __init__
--> 105     m = mapper(class_, *args, **params)
    106     class_.mapper = m
    107     class_.get = m.get

/opt/local/lib/python2.4/site-packages/SQLAlchemy-0.1.5-py2.4.egg/sqlalchemy/mapping/__init__.py in mapper(class_, table, *args, **params)
     53         return class_mapper(class_)
     54 
---> 55     return Mapper(class_, table, *args, **params)
     56 
     57 def clear_mappers():

/opt/local/lib/python2.4/site-packages/SQLAlchemy-0.1.5-py2.4.egg/sqlalchemy/mapping/mapper.py in __init__(self, class_, table, primarytable, properties, primary_key, is_primary, inherits, inherit_condition, extension, order_by, allow_column_override, entity_name, always_refresh, version_id_col, **kwargs)
    223         for key, prop in l:
    224             if getattr(prop, 'key', None) is None:
--> 225                 prop.init(key, self)
    226 
    227         # this prints a summary of the object attributes and how they

/opt/local/lib/python2.4/site-packages/SQLAlchemy-0.1.5-py2.4.egg/sqlalchemy/mapping/mapper.py in init(self, key, parent)
    960         self.key = key
    961         self.parent = parent
--> 962         self.do_init(key, parent)
    963     def do_init(self, key, parent):
    964         """template method for subclasses"""

/opt/local/lib/python2.4/site-packages/SQLAlchemy-0.1.5-py2.4.egg/sqlalchemy/mapping/properties.py in do_init(self, key, parent)
    212 
    213             if self.backref is not None:
--> 214                 self.backref.compile(self)
    215         elif not objectstore.global_attributes.is_class_managed(parent.class_, key):
    216             raise ArgumentError("Non-primary property created for attribute '%s' on class '%s', but that attribute is not managed! Insure that the primary mapper for this class defines this property" % (key, parent.class_.__name__))
/opt/local/lib/python2.4/site-packages/SQLAlchemy-0.1.5-py2.4.egg/sqlalchemy/mapping/properties.py in compile(self, prop)
    884                 cls = EagerLoader
    885             relation = cls(prop.parent, prop.secondary, pj, sj, backref=prop.key, is_backref=True, **self.kwargs)
--> 886             prop.mapper.add_property(self.key, relation);
    887         else:
    888             # else set one of us as the "backreference"

/opt/local/lib/python2.4/site-packages/SQLAlchemy-0.1.5-py2.4.egg/sqlalchemy/mapping/mapper.py in add_property(self, key, prop)
    247                 proplist = self.columntoproperty.setdefault(col.original, [   248                 proplist.append(prop)
--> 249         prop.init(key, self)
    250         
    251     def __str__(self):

/opt/local/lib/python2.4/site-packages/SQLAlchemy-0.1.5-py2.4.egg/sqlalchemy/mapping/mapper.py in init(self, key, parent)
    960         self.key = key
    961         self.parent = parent
--> 962         self.do_init(key, parent)
    963     def do_init(self, key, parent):
    964         """template method for subclasses"""

/opt/local/lib/python2.4/site-packages/SQLAlchemy-0.1.5-py2.4.egg/sqlalchemy/mapping/properties.py in do_init(self, key, parent)
    216             raise ArgumentError("Non-primary property created for attribute '%s' on class '%s', but that attribute is not managed! Insure that the primary mapper for this class defines this property" % (key, parent.class_.__name__))    217 
--> 218         self.do_init_subclass(key, parent)
    219         
    220     def _set_class_attribute(self, class_, key):

/opt/local/lib/python2.4/site-packages/SQLAlchemy-0.1.5-py2.4.egg/sqlalchemy/mapping/properties.py in do_init_subclass(self, key, parent, recursion_stack)
    672         parent._has_eager = True
    673 
--> 674         self.eagertarget = self.target.alias()
    675 #        print "ALIAS", str(self.eagertarget.select()) #selectable.__class__.__name__
    676         if self.secondary:

/opt/local/lib/python2.4/site-packages/SQLAlchemy-0.1.5-py2.4.egg/sqlalchemy/sql.py in alias(self, name)
   1150         return Join(self, right, isouter = True, *args, **kwargs)
   1151     def alias(self, name=None):
-> 1152         return Alias(self, name)
   1153     def select(self, whereclause = None, **params):
   1154         return select([self](])
), whereclause, **params)

/opt/local/lib/python2.4/site-packages/SQLAlchemy-0.1.5-py2.4.egg/sqlalchemy/sql.py in __init__(self, selectable, alias)
    991             alias = n + "_" + hex(random.randint(0, 65535))[2:](2:)
    992         self.name = alias
--> 993         if self.selectable.oid_column is not None:
    994             self.oid_column = self.selectable.oid_column._make_proxy(self)
    995         else:

/opt/local/lib/python2.4/site-packages/SQLAlchemy-0.1.5-py2.4.egg/sqlalchemy/sql.py in _oid_col(self)
   1100         # OID remains a little hackish so far
   1101         if not hasattr(self, '_oid_column'):
-> 1102             if self.engine.oid_column_name() is not None:
   1103                 self._oid_column = schema.Column(self.engine.oid_column_name(), sqltypes.Integer, hidden=True)
   1104                 self._oid_column._set_parent(self)

/opt/local/lib/python2.4/site-packages/SQLAlchemy-0.1.5-py2.4.egg/sqlalchemy/ext/proxy.py in oid_column_name(self)
     32         # oid_column should not be requested before the engine is connected.
     33         # it should ideally only be called at query compilation time.
---> 34         e= self.get_engine()
     35         if e is None:
     36             return None

/opt/local/lib/python2.4/site-packages/SQLAlchemy-0.1.5-py2.4.egg/sqlalchemy/ext/proxy.py in get_engine(self)
    110     def get_engine(self):
    111         if self.storage.engine is None:
--> 112             raise AttributeError('No connection established')
    113         return self.storage.engine
    114

AttributeError: No connection established

If I comment out the relation piece of the mapper, the code imports fine

If I define an engine, and pass it to the table functions, the code works fine

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