On Mar 11, 2014, at 3:50 PM, Bala <[email protected]> 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definition is removed, it is no longer valid to refer to the word "id" within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-relationship
to include this form now.
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