How to create a required (non-optional) relationship attribute?

[cdwilson]

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Example Code

from typing import List, Optional

from sqlmodel import Field, Relationship, Session, SQLModel, create_engine


class Team(SQLModel, table=True):
    id: Optional[int] = Field(default=None, primary_key=True)
    name: str = Field(index=True)
    headquarters: str

    heroes: List["Hero"] = Relationship(back_populates="team")


class Hero(SQLModel, table=True):
    id: Optional[int] = Field(default=None, primary_key=True)
    name: str = Field(index=True)
    secret_name: str
    age: Optional[int] = Field(default=None, index=True)

    team_id: int = Field(default=None, foreign_key="team.id")
    team: Team = Relationship(back_populates="heroes")


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

engine = create_engine(sqlite_url, echo=True)


def create_db_and_tables():
    SQLModel.metadata.drop_all(engine)
    SQLModel.metadata.create_all(engine)


def create_heroes():
    with Session(engine) as session:
        team_preventers = Team(name="Preventers", headquarters="Sharp Tower")

        hero_rusty_man = Hero(
            name="Rusty-Man", secret_name="Tommy Sharp", age=48, team=team_preventers
        )
        hero_spider_boy = Hero(name="Spider-Boy", secret_name="Pedro Parqueador")
        session.add(hero_rusty_man)
        session.add(hero_spider_boy)
        session.commit()

        session.refresh(hero_rusty_man)
        session.refresh(hero_spider_boy)

        print("Created hero:", hero_rusty_man)
        print("Created hero:", hero_spider_boy)


def main():
    create_db_and_tables()
    create_heroes()


if __name__ == "__main__":
    main()

Description

The SQLModel docs mention:

If it was required for a Hero instance to belong to a Team, then the team_id would be int instead of Optional[int].

And the team attribute would be a Team instead of Optional[Team].

When I tried making this change on the tutorial code in the example above, hero_spider_boy is created with team_id=None, even though the intention was for it to be required for a Hero instance to belong to a Team.

Is there a recommended way to create a required relationship (non-optional) that would enforce the requirement that a Hero instance to belongs to a Team in this example?

Operating System

macOS

Operating System Details

Version: 12.6 (21G115)

SQLModel Version

0.0.8

Python Version

Python 3.10.6

Additional Context

I tried removing the default=None attribute from team_id: int = Field(default=None, foreign_key="team.id"), but when I do that, I get a Pylance error saying Argument missing for parameter "team_id":

[cdwilson]

I found a way to achieve this by setting nullable=False on the team_id field:

team_id: int = Field(default=None, foreign_key="team.id", nullable=False)

which results in an error like the following:

sqlalchemy.exc.IntegrityError: (sqlite3.IntegrityError) NOT NULL constraint failed: hero.team_id

I'm brand new to SQLModel (and ORM/databases in general), so if this isn't the correct way to achieve this, please feel free to add a follow up comment.

[tiangolo]

Thanks for reporting back and closing the issue 👍

[Ark-kun]

@cdwilson It looks like you were unable to solve the problem. Could you re-open this issue then?

[cdwilson]

@Ark-kun it's been a long time since I looked at this, but from my comment above, I believe adding nullable=False resulted in the constraint being enforced (i.e. in the example above, the expected error is generated when trying to add hero_spider_boy without a team).

Is there something about this that is not working for you?