This is a duplicate from:
http://stackoverflow.com/questions/43972912/abstract-table-concrete-inheritance-could-not-determine-join-condition-between
I've got following example code:
models.py
class CadastralObject(Base):
__tablename__ = 'cadastral_object'
def __init__(self, cadastral_region, cadastral_district,
cadastral_block, cadastral_object):
self.cadastral_region = cadastral_region
self.cadastral_district = cadastral_district
self.cadastral_block = cadastral_block
self.cadastral_object = cadastral_object
# this is a combined PK
cadastral_region = Column(Integer, primary_key=True, index=True)
cadastral_district = Column(Integer, primary_key=True, index=True)
cadastral_block = Column(Integer, primary_key=True, index=True)
cadastral_object = Column(Integer, primary_key=True, index=True)
encumbrances = relationship("Encumbrance")
class Encumbrance(Base):
__tablename__ = 'encumbrance'
id = Column(Integer, primary_key=True, index=True)
def __init__(self, cadastral_object):
self.parent_cadastral_region = cadastral_object.cadastral_region
self.parent_cadastral_district = cadastral_object.
cadastral_district
self.parent_cadastral_block = cadastral_object.cadastral_block
self.parent_cadastral_object = cadastral_object.cadastral_object
# FK fields
parent_cadastral_region = Column(Integer, nullable=False)
parent_cadastral_district = Column(Integer, nullable=False)
parent_cadastral_block = Column(Integer, nullable=False)
parent_cadastral_object = Column(Integer, nullable=False)
parent_object = relationship(CadastralObject)
__table_args__ = (ForeignKeyConstraint(
[
parent_cadastral_region,
parent_cadastral_district,
parent_cadastral_block,
parent_cadastral_object],
[
CadastralObject.cadastral_region,
CadastralObject.cadastral_district,
CadastralObject.cadastral_block,
CadastralObject.cadastral_object]),
{}
)
this code works as intended:
main.py
c = CadastralObject(1, 2, 3, 4)
session.add(c)
e = Encumbrance(c)
session.add(e)
session.commit()
print(c.encumbrances)
print(e.parent_object)
results:
[<app.models.Encumbrance object at 0x000001C9B820BCC0>]
<app.models.CadastralObject object at 0x000001C9B820BB00>
however, when I'm trying convert my code to Concrete Inheritance:
imodels.py
class iCadastralObject(AbstractConcreteBase, Base):
def __init__(self, cadastral_region, cadastral_district,
cadastral_block, cadastral_object):
self.cadastral_region = cadastral_region
self.cadastral_district = cadastral_district
self.cadastral_block = cadastral_block
self.cadastral_object = cadastral_object
# this is a combined PK
cadastral_region = Column(Integer, primary_key=True, index=True)
cadastral_district = Column(Integer, primary_key=True, index=True)
cadastral_block = Column(Integer, primary_key=True, index=True)
cadastral_object = Column(Integer, primary_key=True, index=True)
@declared_attr
def encumbrances(self):
return relationship("iEncumbrance")
class Building(iCadastralObject):
__tablename__ = 'building'
__mapper_args__ = {
'polymorphic_identity': 'building',
'concrete': True
}
@declared_attr
def encumbrances(self):
return relationship("iEncumbrance")
class Flat(iCadastralObject):
__tablename__ = 'flat'
__mapper_args__ = {
'polymorphic_identity': 'flat',
'concrete': True
}
@declared_attr
def encumbrances(self):
return relationship("iEncumbrance")
class Construction(iCadastralObject):
__tablename__ = 'construction'
__mapper_args__ = {
'polymorphic_identity': 'construction',
'concrete': True
}
class iEncumbrance(Base):
__tablename__ = 'iencumbrance'
id = Column(Integer, primary_key=True, index=True)
def __init__(self, cadastral_object):
self.parent_cadastral_region = cadastral_object.cadastral_region
self.parent_cadastral_district = cadastral_object.
cadastral_district
self.parent_cadastral_block = cadastral_object.cadastral_block
self.parent_cadastral_object = cadastral_object.cadastral_object
# FK fields
parent_cadastral_region = Column(Integer, nullable=False)
parent_cadastral_district = Column(Integer, nullable=False)
parent_cadastral_block = Column(Integer, nullable=False)
parent_cadastral_object = Column(Integer, nullable=False)
parent_object = relationship(iCadastralObject)
__table_args__ = (ForeignKeyConstraint(
[
parent_cadastral_region,
parent_cadastral_district,
parent_cadastral_block,
parent_cadastral_object],
[
iCadastralObject.cadastral_region,
iCadastralObject.cadastral_district,
iCadastralObject.cadastral_block,
iCadastralObject.cadastral_object]),
{}
)
I'm getting an error on "from app.imodels import Building"
sqlalchemy.exc.NoForeignKeysError: Could not determine join condition
between parent/child tables on relationship iCadastralObject.encumbrances -
there are no foreign keys linking these tables. Ensure that referencing
columns are associated with a ForeignKey or ForeignKeyConstraint, or
specify a 'primaryjoin' expression.
--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
Example. See http://stackoverflow.com/help/mcve for a full description.
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