Below is a simplified case of a problem (bug?) I am running into. I
have a polymorphic schema using joined-table inheritance. In my OO
layer, a Group is an Agent, and a Lab is a Group. In the DB layer,
Lab doesn't actually need to hold any extra information so it doesn't
need a separate table.
Instead, I would like to map the Lab object to the 'groups' table and
select only those types that are identified as a lab by the 'type'
discriminator column in 'agents' table. I want,t hen, to map Lab to a
selectable. However, when I try to create and flush a Lab instance
with the setup below, it is obvious that the attributes that should
map into the groups table aren't getting collected into the INSERT
statement correctly.
If I change `lab_select` to the simple join without the select
statement, the Lab instance is persisted correctly. Of course, this
does nothing for the need to filter out non-lab entries. Similarly,
if I create a useless extra table called `labs` and map to that
instead, the INSERT works
Any ideas on how to adjust the `lab_select` statement below so that
this works?
Thanks!
-Jason
----
import sqlalchemy as sa
from sqlalchemy import types as t
from sqlalchemy import orm
engine = sa.create_engine('sqlite:///:memory:', echo=True)
metadata = sa.MetaData()
agents = sa.Table('agents', metadata,
sa.Column('id', t.Integer,
sa.Sequence('agents_id_seq', optional=True),
primary_key=True),
sa.Column('type', t.Unicode(50),
sa.CheckConstraint("type IN ('agent', 'person', 'group',
'group_org', \
'group_lab', 'group_contactlist')"), nullable=False),
sa.Column('notes', t.UnicodeText),
)
groups = sa.Table('groups', metadata,
sa.Column('id', t.Integer, unique=True),
sa.Column('short_name', t.Unicode(50)),
sa.Column('name', t.Unicode(255), nullable=False),
sa.Column('group_status', t.Unicode(50),
sa.CheckConstraint("group_status IN ('active', 'not active',
'closed')"),
default=u'active', nullable=False),
sa.Column('description', t.UnicodeText),
sa.PrimaryKeyConstraint('id'),
sa.ForeignKeyConstraint(['id'], ['agents.id'],
onupdate="CASCADE", ondelete="CASCADE")
)
class Agent(object):
pass
class Group(Agent):
pass
class Lab(Group):
pass
def map_agent_classes():
orm.mapper(Agent, agents,
polymorphic_on=agents.c.type,
polymorphic_identity=u"agent",
)
orm.mapper(Group, groups,
inherits=Agent,
polymorphic_identity=u"group",
)
lab_select =
agents.outerjoin(groups).select(agents.c.type==u'group_lab',\
use_labels=True).alias('labs')
orm.mapper(Lab, lab_select,
inherits=Group,
polymorphic_identity=u"group_lab",
)
map_agent_classes()
metadata.create_all(engine)
Session = orm.sessionmaker(bind=engine)
sess = Session()
lab = Lab()
lab.name = u"Lab Name"
lab.short_name = u"lab"
sess.add(lab)
sess.flush()
--------
IntegrityError: (IntegrityError) groups.name may not be NULL u'INSERT
INTO groups (id, short_name, name, group_status, description) VALUES
(?, ?, ?, ?, ?, ?)' [1, None, None, None, None]
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