Non-sqlalchemy types unable to be defined in base data models

[jtpavlock]

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Example Code

#!/usr/bin/env python3

from typing import Optional, Any

import sqlalchemy
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.ext.mutable import MutableDict, MutableSet
from sqlalchemy.orm import sessionmaker
from sqlalchemy import JSON, Column
from sqlmodel import SQLModel, Field, create_engine, Relationship

Session = sessionmaker()
Base = declarative_base()


class BaseTrack(SQLModel):
    title: str


class Track(BaseTrack, table=True):
    id: Optional[int] = Field(default=None, primary_key=True)
    title: int
    album_id: Optional[int] = Field(default=None, foreign_key="album.id")
    album: "Album" = Relationship(back_populates="tracks")


class BaseAlbum(SQLModel):
    tracks: list[BaseTrack]


class Album(BaseAlbum, table=True):
    id: Optional[int] = Field(default=None, primary_key=True)
    tracks: Optional[list[Track]] = Relationship(back_populates="album")


engine = create_engine("sqlite:///:memory:")
Session.configure(bind=engine)
SQLModel.metadata.create_all(engine)
session = Session()

track = Track(id=1, title=2, album_id=1, album=Album(id=1))

session.add(track)
session.commit()

Description

The above code gives the following error:

Traceback (most recent call last):
  File "/home/jacob/src/Moe/test_custom.py", line 31, in <module>
    class Album(BaseAlbum, table=True):
  File "/home/jacob/src/Moe/.venv/lib/python3.9/site-packages/sqlmodel/main.py", line 293, in __new__
    col = get_column_from_field(v)
  File "/home/jacob/src/Moe/.venv/lib/python3.9/site-packages/sqlmodel/main.py", line 421, in get_column_from_field
    sa_type = get_sqlachemy_type(field)
  File "/home/jacob/src/Moe/.venv/lib/python3.9/site-packages/sqlmodel/main.py", line 414, in get_sqlachemy_type
    raise ValueError(f"The field {field.name} has no matching SQLAlchemy type")
ValueError: The field tracks has no matching SQLAlchemy type

Because I'm overriding tracks to be a column in my actual database class, this should not error.

Operating System

Linux

Operating System Details

No response

SQLModel Version

0.08

Python Version

3.9.13

Additional Context

Looks to have been caused by #18

[antont]

Why do you want to have the relationship in the base? I've simply omitted them from there, as inherit Base to the Create models, which are the POST data that the frontend uses to create objects. Then Read models have such definitions for the relationships that we wanna expose in the API.

[jtpavlock]

I'm using the base model to represent a subset of data useful for certain operations that don't require connection to a database or the entire model to be present.

[tiangolo]

Yep, you shouldn't do that. If a descendant of the base class is completely overriding the field, then it should probably not be there. In this particular case, it should certainly not be there on the base class.

You would have one field for the table model and another field for the class that inherits from base that needs the relationship.

If you want to avoid duplicating the field with relationships you would need a base for everything, and another "sub-base" only for data models (not tables) that includes the relationship.

[github-actions]

Assuming the original need was handled, this will be automatically closed now. But feel free to add more comments or create new issues or PRs.