On Tuesday, March 11, 2014 4:39:54 PM UTC-7, Michael Bayer wrote:
>
> you need to name the “secondary” table as it’s name in the MetaData
> collection, not the variable name you’ve assigned it to, when configuring
> with string arguments.
>
>
> On Mar 11, 2014, at 6:50 PM, Bala <bal...@gmail.com <javascript:>> wrote:
>
> Hi Michael, thanks for the prompt reply.
>
> However, When I tried according to the suggestion, I get this error:
>
> 45 class Groups(ModelBase, VersionColumnMixin):
> 46 domain_id = sa.Column(sa.String(36),
> DefaultClause('default'), nullable=False)
> 47 description = sa.Column(sa.Text)
> 48 date_created = sa.Column(sa.DateTime)
> 49 group_name = sa.Column(sa.String(64), nullable=False,
> index=True)
> 50 child_groups = relationship('Groups',
> secondary=groups_and_groups_assoc_table,
> 51 primaryjoin=
> *"Groups.id==groups_and_groups_assoc_table.c.parent_group_id"*,
> 52 secondaryjoin=
> *"Groups.id==groups_and_groups_assoc_table.c.child_group_id"*,
> 53 backref='parent_groups')
> 54 __table_args__ = (sa.UniqueConstraint('domain_id',
> 'group_name'),)
>
> Traceback (most recent call last):
> File "./selfref4.py", line 67, in <module>
> g1 = Groups(description='1234', group_name='group1')
> File "<string>", line 2, in __init__
> File
> "/usr/lib64/python2.6/site-packages/sqlalchemy/orm/instrumentation.py",
> line 322, in _new_state_if_none
> state = self._state_constructor(instance, self)
> File
> "/usr/lib64/python2.6/site-packages/sqlalchemy/util/langhelpers.py", line
> 689, in __get__
> obj.__dict__[self.__name__] = result = self.fget(obj)
> ...
> ...File
> "/usr/lib64/python2.6/site-packages/sqlalchemy/ext/declarative/clsregistry.py",
>
> line 275, in __call__
> (self.prop.parent, self.arg, n.args[0], self.cls)
> *sqlalchemy.exc.InvalidRequestError:* When initializing mapper
> Mapper|Groups|groups, expression
> 'Groups.id==groups_and_groups_assoc_table.c.parent_group_id' failed to
> locate a name ("name 'groups_and_groups_assoc_table' is not defined"). If
> this is a class name, consider adding this relationship() to the <class
> '__main__.Groups'> class after both dependent classes have been defined.
>
>
>
>
> On Tuesday, March 11, 2014 2:10:52 PM UTC-7, Michael Bayer wrote:
>>
>>
>> On Mar 11, 2014, at 3:50 PM, Bala <bal...@gmail.com> wrote:
>>
>> 45 class Groups(ModelBase, VersionColumnMixin):
>> 46 *id = sa.Column('id', sa.Integer, Sequence('id_seq'),
>> primary_key=True)*
>> 47 domain_id = sa.Column(sa.String(36),
>> DefaultClause('default'), nullable=False)
>> 48 description = sa.Column(sa.Text)
>> 49 date_created = sa.Column(sa.DateTime)
>> 50 group_name = sa.Column(sa.String(64), nullable=False,
>> index=True)
>> 51 child_groups = relationship('Groups',
>> secondary=groups_and_groups_assoc_table,
>> 52
>> primaryjoin=id==groups_and_groups_assoc_table.c.parent_group_id,
>> 53
>> secondaryjoin=id==groups_and_groups_assoc_table.c.child_group_id,
>> 54 backref='parent_groups’)
>>
>>
>> here, when the definition of the Python identifier “id” within the Groups
>> class definition is removed, it is no longer valid to refer to the word
>> “id” within the “primaryjoin” and “secondaryjoin” conditions, as “id” is
>> not defined. The reason it seems to be defined is that it is resolving to
>> the Python built in function “id”. Unfortunately the exception message
>> isn’t being too smart here, interpreting “id” as just another literal value
>> like the number “3” so you don’t see it, it wouldn’t be a bad idea for SQLA
>> to detect this kind of thing but that is actually somewhat difficult as it
>> is valid for an expression to refer to a callable.
>>
>> Since “id” is not yet defined within the class body of Groups you need to
>> specify conditions using a string:
>>
>> class Groups(ModelBase, VersionColumnMixin):
>> domain_id = sa.Column(sa.String(36), DefaultClause('default'),
>> nullable=False)
>> description = sa.Column(sa.Text)
>> date_created = sa.Column(sa.DateTime)
>> group_name = sa.Column(sa.String(64), nullable=False, index=True)
>> child_groups = relationship('Groups',
>> secondary=groups_and_groups_assoc_table,
>>
>> primaryjoin="Groups.id==groups_and_groups.c.parent_group_id",
>>
>> secondaryjoin="Groups.id==groups_and_groups.c.child_group_id",
>> backref='parent_groups')
>> __table_args__ = (sa.UniqueConstraint('domain_id', 'group_name'),)
>>
>>
>> i’m updating the document at
>> http://docs.sqlalchemy.org/en/rel_0_9/orm/relationships.html#self-referential-many-to-many-relationshipto
>> include this form now.
>>
>>
>>
>>
>>
>>
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