[Python] How to make alembic autogenerate foreing key relations?

I'm trying to get Alembic to autogenerate a first version of my database, which is at this point very simple. The command works, and generates a migration with all of my tables and columns, except all ForeignKey relations.

My code looks like this:

from typing import List
from sqlalchemy import String
from sqlalchemy.orm import DeclarativeBase, mapped_column, Mapped, relationship


class Base(DeclarativeBase):
pass


class DBUnitCategory(Base):
__tablename__ = 'unit_category'

id: Mapped[int] = mapped_column(primary_key=True)
name: Mapped[str] = mapped_column(String(20))

unit_id: Mapped[List["DBUnit"]] = relationship(back_populates="category_id")

class DBUnit(Base):
__tablename__ = 'unit'

id: Mapped[int] = mapped_column(primary_key=True)
name: Mapped[str] = mapped_column(String(12))

category_id: Mapped[DBUnitCategory] = relationship(back_populates="unit_id")


And the generated upgrade migration looks like this:

def upgrade() -> None:
# ### commands auto generated by Alembic - please adjust! ###

op.create_table('unit',
sa.Column('id', sa.Integer(), nullable=False),
sa.Column('name', sa.String(length=12), nullable=False),
sa.PrimaryKeyConstraint('id')
)
op.create_table('unit_category',
sa.Column('id', sa.Integer(), nullable=False),
sa.Column('name', sa.String(length=20), nullable=False),
sa.PrimaryKeyConstraint('id')
)
# ### end Alembic commands ###


def downgrade() -> None:
# ### commands auto generated by Alembic - please adjust! ###
op.drop_table('unit_category')
op.drop_table('unit')


I don't think I messed up my definitions, it looks like in the tutorial to me. There is no issue with this on the github, so I don't understand what's going on. Is it related to the fact I'm using an sqlite database?

Continue reading...