On Jun 5, 2008, at 11:18 AM, Tomer wrote:
>
> Hi,
>
> I have two tables: Image and PersistentImage, where the latter
> inherits the former. In addition, PersistentImage has a foreign key to
> itself (ie, all PersistentImage objects form a hierarchy among
> themselves). I haven't been able to get this to work - first it
> complained about wanting a primaryjoin, then it seemed to get confused
> between the parent/children relation among PersistentImage objects and
> the inheritance between PersistentImage and Image. Here are my
> mappers:
>
> mapper(
> Image,
> imageTable,
> polymorphic_on=imageTable.c.type,
> polymorphic_identity='Image'
> )
>
> mapper(
> PersistentImage,
> persistentImageTable,
> inherits=Image,
> polymorphic_identity='PersistentImage',
> properties={
> 'children': relation(PersistentImage, backref='parent')
> })
>
> And here are the actual table definitions:
>
> imageTable = Table('Images', metadata,
> Column('id', Integer, primary_key=True),
> Column('name', String(256), nullable=False),
> Column('type', String(30), nullable=False)
> )
>
> persistentImageTable = Table('PersistentImages', metadata,
> Column('id', Integer, ForeignKey('Images.id'), primary_key=True),
> Column('parentId', Integer, ForeignKey('PersistentImages.id')),
> Column('userId', Integer, ForeignKey('Users.id'), nullable=False)
> )
here it is:
mapper(PersistentImage, persistentImageTable, inherits=Image,
inherit_condition=persistentImageTable.c.id==imageTable.c.id,
polymorphic_identity='PersistentImage',
properties={
'children':relation(PersistentImage,
primaryjoin=persistentImageTable.c.parentId==persistentImageTable.c.id,
backref=backref('parent',
primaryjoin
=persistentImageTable.c.parentId==persistentImageTable.c.id,
remote_side=[persistentImageTable.c.id])
)
})
SQLA would probably slightly happier if you had the "parentId" foreign
key referencing Images.id instead of PersistentImages.id but this
should not be required.
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