On Sep 27, 2006, at 4:15 PM, Matias Hermanrud Fjeld wrote:
> Here is (part of) the table SA is working with.
>
> Table('categories',
> BoundMetaData(),
> Column('categories_id',<sqlalchemy.databases.mysql.MSInteger object
> at
> 0x4060a5ec>,key='categories_id',primary_key=True,nullable=False,hidden
> =False,default=None,onupdate=None),
> Column('parent_id',<sqlalchemy.types.Integer object at
> 0x4060742c>,ForeignKey
> ('categories.categories_id'),key='parent_id',primary_key=False,nullabl
> e=True,hidden=False,default=None,onupdate=None),
> [snip uninteresting columns]
> schema=None)
>
> The mapper:
>
> sa.mapper(
> Category, categories, properties=dict(
> children=sa.relation(
> Category, backref=sa.backref('parent', uselist=False)
> ),
> [snip]
> )
> )
>
> Is there anything special I have to do to tell SA that the
> dependency should only go one way?
>
yeah, becuase this mapper is self-referring, the "parent" backref
needs a clue that the relationship is in the opposite direction, like
this:
sa.mapper(
Category, categories, properties=dict(
children=sa.relation(
Category, backref=sa.backref('parent', uselist=False,
foreignkey=categories.c.categories_id)
),
[snip]
)
)
see the example in http://www.sqlalchemy.org/docs/
adv_datamapping.myt#advdatamapping_recursive for this, as well as the
examples in the /examples directory of the distribution.
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