a join is of the form:
table1.join(table2, onclause)
such as
subscriber_table.join(address_table,
and_(address_table.c.subscriber_id==subscriber.c.id,
address_table.c.type=='MAIN'))
but unfortunately current relation() code does not support a join of X/
Y to Y, unless the join of X/Y is assembled via joined table
inheritance. As a workaround, you can wrap your join() in an
aliased select(). A fix may be available in the next 10 minutes or
maybe not.
You also could forego the complexity of mapping to a join and just
modify your Subscriber class to break up the "addresses" collection
amongst a proxy of the "MAIN" element and a list of the remaining
elements. an attribute_mapped_collection could help to accomplish
this nicely.
On Jan 28, 2009, at 7:22 PM, GHZ wrote:
>
> I have a subscriber and address table.
>
> a subscriber will have one and only one 'MAIN' address.
> I want the subscriber and MAIN address to be represented by one class
> 'Subscriber'. However, I want that class to have a collection
> 'addresses' which contains other addresses (e.g. old addresses) - (it
> can include the 'MAIN' address too .. or not.. I don't care)
>
> subscriber_table = Table('subscriber', metadata,
> Column('id', primary_key=True),
> autoload=True)
>
> address_table = Table('address',
> metadata,
> Column('subscriber_id', ForeignKey
> ('subscriber.id'), primary_key=True),
> Column('address_type', primary_key=True),
> autoload=True)
>
>
>
> subscriber_with_default_address = sql.join( subscriber_table.c.id
> == address_table.c.subscriber_id).??? <- something to say
> address_table.type is 'MAIN'
>
> mapper(Address, address_table)
>
> mapper(Subscriber, subscriber_and_address, properties={
> 'id':[subscriber_table.c.id, address_table.c.subscriber_id],
> 'addresses' : relation(Address, collection_class=Addresses,
> backref='customer')
> })
>
> a) I can't quite figure out how to say (address.type is default)
> b) even without this I get:
>
> sqlalchemy.exc.ArgumentError: Can't determine relation direction for
> relationshi
> p 'Subscriber.addresses' - foreign key columns are present in both the
> parent an
> d the child's mapped tables. Specify 'foreign_keys' argument.
>
> if I do specify foreign_keys parameter to the relation function, then
> I still get the same.
>
> Thanks
>
>
> >
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