Hello,
I have a question about using multiple polymorphic tables with different
parents which relate to the the same parent table but other polymorphic
child.
I have two tables staff (class Staff) and contract (class Contract).
The Staff table has an identity manager (class Manager) and the contract
table has an identity peon (class Peon).
I have a third table called payments. Payments has two identities
identity StatusReport and BillableHours.
I want to have StausReport have a relationship to Peon
ForeignKey('contract.id') and the BillableHours have a relationship to
Manager ForeignKey('staff.id')
The relationships look like this:
staff.id => payments.user_id
contract.id => payments.user_id
payments.user_id => staff.id
payments.user_id => contract.id
I am using SQLAlchemy v0.5.8 on Python v2.6
Here is an *example* of one of the tests i have tried. I hope it gives
a better idea of what I am tring to do (and is not just confusing).
I get failures about specifying "foreign_keys" or "Could not locate any
equated locally mapped column pairs..."
--------------------------------------------------------------
from sqlalchemy import MetaData, orm, schema
from sqlalchemy.types import Integer, String
from sqlalchemy.schema import Column, Sequence, ForeignKey
import sqlalchemy as sa
from sqlalchemy.orm import sessionmaker, relation
from sqlalchemy.ext.declarative import declarative_base
engine = sa.create_engine( 'sqlite://' )
metadata = MetaData( )
Base = declarative_base( metadata = metadata )
Session = sessionmaker( )
Session.configure( bind = engine )
def create( ):
Base.metadata.create_all( engine )
class Staff( Base ):
__tablename__ = 'staff'
id = Column( Integer, Sequence( 'user_seq' ),
nullable=False, primary_key=True )
name = Column( String, nullable=False )
type = Column( String, nullable=False )
__mapper_args__ = {'polymorphic_on': type }
class Manager( Staff ):
__mapper_args__ = {'polymorphic_identity': 'manager'}
Billables = relation( 'BillableHours' )
class Contract( Base ):
__tablename__ = 'contract'
id = Column( Integer, Sequence( 'contract_seq' ),
nullable=False, primary_key=True )
type = Column( String, nullable=False )
__mapper_args__ = {'polymorphic_on': type }
class Peon( Contract ):
__mapper_args__ = {'polymorphic_identity': 'peon'}
StatusReports = relation( 'StatusReport' )
class Payments( Base ):
__tablename__ = 'payments'
id = Column( Integer, Sequence( 'payments_seq' ),
nullable=False, primary_key=True )
type = Column( String, nullable=False )
__mapper_args__ = {'polymorphic_on': type }
class StatusReport( Payments ):
__mapper_args__ = {'polymorphic_identity': 'status'}
user = Column( Integer, ForeignKey('contract.id'), nullable=False )
job = Column( String, nullable=False, default="offshore" )
hrs = Column( Integer, nullable=False, default=0 )
Peons = relation( 'Peon' )
class BillableHours( Payments ):
__mapper_args__ = {'polymorphic_identity': 'billable'}
user = Column( Integer, ForeignKey('staff.id'), nullable=False )
job = Column( String, nullable=False )
hrs = Column( Integer, nullable=False, default=8 )
Managers = relation( 'Manager' )
--------------------------------------------------------------
Thanks.
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