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1. zopyx

   added

   questionFurther information is requestedFurther information is requested

   on Sep 6, 2022
2. daniil-berg commented on Sep 6, 2022

   

   daniil-berg

   on Sep 6, 2022

   Contributor

   More actions

   I can confirm. Here is a simplified version for testing (compatible with Python 3.7+):

   from typing import List, Optional
   
   from sqlmodel import Field, SQLModel, create_engine, Session, Relationship
   
   
   class Foo(SQLModel, table=True):
       id: Optional[int] = Field(primary_key=True)
   
       bars: List["Bar"] = Relationship(back_populates="foo")
   
   
   class Bar(SQLModel, table=True):
       __mapper_args__ = {
           "polymorphic_on": "type",
           "polymorphic_identity": "x",
       }
   
       id: Optional[int] = Field(primary_key=True)
       type: str = Field(default="x")
   
       foo_id: Optional[int] = Field(foreign_key="foo.id")
       foo: Optional[Foo] = Relationship(back_populates="bars")
   
   
   class BarY(Bar, table=True):
       __mapper_args__ = {
           "polymorphic_identity": "y",
       }
   
   
   class BarZ(Bar, table=True):
       __mapper_args__ = {
           "polymorphic_identity": "z",
       }
   
   
   db_url = f"sqlite:///:memory:"
   engine = create_engine(db_url, echo=True)
   SQLModel.metadata.create_all(engine)
   
   
   with Session(engine) as session:
       foo = Foo()
       foo.bars.extend([BarY(), Bar()])
       session.add(foo)
       session.commit()

   The full error: (Click to expand)

   Traceback (most recent call last):
     File "/home/daniil/coding/sqlmodel/polymorphic.py", line 45, in <module>
       session.add(foo)
     File "/home/daniil/.cache/pypoetry/virtualenvs/sqlmodel-TV15XYpK-py3.10/lib/python3.10/site-packages/sqlalchemy/orm/session.py", line 2626, in add
       self._save_or_update_state(state)
     File "/home/daniil/.cache/pypoetry/virtualenvs/sqlmodel-TV15XYpK-py3.10/lib/python3.10/site-packages/sqlalchemy/orm/session.py", line 2642, in _save_or_update_state
       for o, m, st_, dct_ in mapper.cascade_iterator(
     File "/home/daniil/.cache/pypoetry/virtualenvs/sqlmodel-TV15XYpK-py3.10/lib/python3.10/site-packages/sqlalchemy/orm/mapper.py", line 3230, in cascade_iterator
       queue = deque(
     File "/home/daniil/.cache/pypoetry/virtualenvs/sqlmodel-TV15XYpK-py3.10/lib/python3.10/site-packages/sqlalchemy/orm/relationships.py", line 2020, in cascade_iterator
       instance_mapper = instance_state.manager.mapper
     File "/home/daniil/.cache/pypoetry/virtualenvs/sqlmodel-TV15XYpK-py3.10/lib/python3.10/site-packages/sqlalchemy/util/langhelpers.py", line 1113, in __get__
       obj.__dict__[self.__name__] = result = self.fget(obj)
     File "/home/daniil/.cache/pypoetry/virtualenvs/sqlmodel-TV15XYpK-py3.10/lib/python3.10/site-packages/sqlalchemy/orm/instrumentation.py", line 204, in mapper
       raise exc.UnmappedClassError(self.class_)
   sqlalchemy.orm.exc.UnmappedClassError: Class '__main__.BarY' is not mapped
   

   Here is an analogous version in pure SQLAlchemy working with no errors: (Click to expand)

   from sqlalchemy.engine.create import create_engine
   from sqlalchemy.orm import relationship
   from sqlalchemy.orm.decl_api import declarative_base
   from sqlalchemy.sql.schema import Column, ForeignKey
   from sqlalchemy.orm.session import Session
   from sqlalchemy.sql.sqltypes import Integer, String
   
   
   Base = declarative_base()
   
   
   class Foo(Base):
       __tablename__ = 'foo'
       id = Column(Integer, primary_key=True)
   
       bars = relationship("Bar", back_populates="foo")
   
   
   class Bar(Base):
       __tablename__ = 'bar'
       __mapper_args__ = {
           "polymorphic_on": "type",
           "polymorphic_identity": "x",
       }
   
       id = Column(Integer, primary_key=True)
       type = Column(String, default="x")
   
       foo_id = Column(ForeignKey("foo.id"))
       foo = relationship("Foo", back_populates="bars")
   
   
   class BarY(Bar):
       __mapper_args__ = {
           "polymorphic_identity": "y",
       }
   
   
   class BarZ(Bar):
       __mapper_args__ = {
           "polymorphic_identity": "z",
       }
   
   
   db_url = f"sqlite:///:memory:"
   engine = create_engine(db_url, echo=True)
   Base.metadata.create_all(engine)
   
   
   with Session(engine) as session:
       foo = Foo()
       foo.bars.extend([BarY(), Bar()])
       session.add(foo)
       session.commit()

   ---

   Interestingly, you get a different error, if you instead just try to instantiate a BarY object:

   ...
   with Session(engine) as session:
       bar = BarY()
       session.add(bar)
       session.commit()

   The full error: (Click to expand)

   Traceback (most recent call last):
     File "/home/daniil/coding/sqlmodel/polymorphic.py", line 46, in <module>
       bar = BarY()
     File "<string>", line 4, in __init__
     File "/home/daniil/.cache/pypoetry/virtualenvs/sqlmodel-TV15XYpK-py3.10/lib/python3.10/site-packages/sqlalchemy/orm/state.py", line 481, in _initialize_instance
       with util.safe_reraise():
     File "/home/daniil/.cache/pypoetry/virtualenvs/sqlmodel-TV15XYpK-py3.10/lib/python3.10/site-packages/sqlalchemy/util/langhelpers.py", line 70, in __exit__
       compat.raise_(
     File "/home/daniil/.cache/pypoetry/virtualenvs/sqlmodel-TV15XYpK-py3.10/lib/python3.10/site-packages/sqlalchemy/util/compat.py", line 208, in raise_
       raise exception
     File "/home/daniil/.cache/pypoetry/virtualenvs/sqlmodel-TV15XYpK-py3.10/lib/python3.10/site-packages/sqlalchemy/orm/state.py", line 479, in _initialize_instance
       return manager.original_init(*mixed[1:], **kwargs)
     File "<string>", line 6, in __init__
     File "/home/daniil/coding/sqlmodel/sqlmodel/main.py", line 518, in __init__
       setattr(__pydantic_self__, key, value)
     File "/home/daniil/coding/sqlmodel/sqlmodel/main.py", line 532, in __setattr__
       set_attribute(self, name, value)
     File "/home/daniil/.cache/pypoetry/virtualenvs/sqlmodel-TV15XYpK-py3.10/lib/python3.10/site-packages/sqlalchemy/orm/attributes.py", line 2256, in set_attribute
       state.manager[key].impl.set(state, dict_, value, initiator)
   AttributeError: 'NoneType' object has no attribute 'set'
   

   ---

   I tried debugging the SQLModelMetaclass.__new__ method, to see if the __mapper_args__ end up on the resulting class, and it seems like they are. I checked this line here:

   new_cls = super().__new__(cls, name, bases, dict_used, **config_kwargs)

   When setting up Bar for example, the new_cls.__dict__ contains the key value pair:

   __mapper_args__: {'polymorphic_on': 'type', 'polymorphic_identity': 'x'}
   

   So that seems not to be the issue.

   This is all I got so far.
3. zopyx commented on Sep 6, 2022

   

   zopyx

   on Sep 6, 2022

   Author

   More actions

   Someone helped me out with a slightly modified version that works for me:

   from typing import Optional
   import uuid
   from typing import List
   
   from sqlmodel import Field, SQLModel, create_engine, Session, Relationship
   from uuid import UUID
   from sqlalchemy.orm import registry
   mapper_registry = registry()
   
   class InvoiceRequest(SQLModel, table=True):
   
       __tablename__ = "invoice_requests"
   
       id: UUID = Field(default_factory=uuid.uuid4, primary_key=True)
       product: str | None = None
       request_type: str | None = None
   
       invoices : List["Invoice"] = Relationship(back_populates="invoice_request")
   
       def add_invoices(self):
           self.invoices.append(InvoiceReversal())
           self.invoices.append(InvoiceCorrection())
   
   
   class Invoice(SQLModel, table=True):
   
   #    __tablename__ = "invoices"
   
       id: UUID = Field(default_factory=uuid.uuid4, primary_key=True)
       invoice_type: str = Field(default="regular")
   
       invoice_request_id: UUID | None = Field(default=None, foreign_key="invoice_requests.id")
       invoice_request: InvoiceRequest = Relationship(back_populates="invoices")
   
       __mapper_args__ = {
           "polymorphic_on": 'invoice_type',
           "polymorphic_identity": "regular",
       }
   
   @mapper_registry.mapped
   class InvoiceReversal(Invoice, table=True):
       invoice_types: str = Field(default="regular")
       __mapper_args__ = {
           "polymorphic_identity": "reversal",
           "inherit_condition": invoice_types == Invoice.invoice_type
       }
   
   @mapper_registry.mapped
   class InvoiceCorrection(Invoice, table=True):
       invoice_types: str = Field(default="correction")
       __mapper_args__ = {
           "polymorphic_identity": "correction",
           "inherit_condition": invoice_types == Invoice.invoice_type
       }
   
4. mxdev88 commented on Jul 28, 2023

   

   mxdev88

   on Jul 28, 2023

   More actions

   I tried this workaround with @mapper_registry.mapped but I get "sqlalchemy.exc.ProgrammingError: (psycopg2.errors.UndefinedColumn) column xxx does not exist".

   With "inherit_condition" SQLAlchemy maked the correct join but thinks all columns are in the child table. There also a warning on start up, "SAWarning: Implicitly combining column parent.id with column child.id under attribute 'id'. Please configure one or more attributes for these same-named columns explicitly."

   Any idea how to make this work?
5. sunkunxi commented on Jul 3, 2024

   

   sunkunxi

   on Jul 3, 2024

   More actions

   Hello~, the current version is sqlmodel 0.0.19. Does anyone have idea about how to solve this?
   @mapper_registry.mapped not work for me
6. fastapi

   locked and limited conversation to collaborators on May 18, 2026
7. tiangolo

   converted this issue into a discussion #1960 on May 18, 2026