ValueError: <class 'list'> has no matching SQLAlchemy type

[mockingjet]

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• I already checked if it is not related to SQLModel but to SQLAlchemy.

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Example Code

from sqlmodel import Field, Relationship, SQLModel

class Role(SQLModel, table=True):
    name: str = Field(index=True, unique=True)
    permissions: list["Permission"] = Relationship(
        back_populates="roles",
        link_model=RolePermissionLink,
    )

class Permission(SQLModel, table=True):
    name: str = Field(index=True, unique=True)
    roles: list[Role] = Relationship(
        back_populates="permissions",
        link_model=RolePermissionLink,
    )

Description

Either permissions: list["Permission"] or roles: list[Role] is not working and emits this error:

File "/usr/local/lib/python3.12/site-packages/sqlmodel/main.py", line 615, in get_sqlalchemy_type
raise ValueError(f"{type_} has no matching SQLAlchemy type")
ValueError: <class 'list'> has no matching SQLAlchemy type

Operating System

Linux

Operating System Details

No response

SQLModel Version

0.0.18

Python Version

3.12.4

Additional Context

No response

[ixycoexzckwpmlcu]

I've tried to reproduce your example but couldn't. If I run your example verbatim, it errors with NameError: name 'RolePermissionLink' is not defined¹. If I change your example to the following:

from sqlmodel import Field, Relationship, SQLModel

class RolePermissionLink(SQLModel, table=True):
    role_id: str = Field(foreign_key="role.id", primary_key=True)
    permission_id: str = Field(foreign_key="permission.id", primary_key=True)

class Role(SQLModel, table=True):
    id: int = Field(primary_key=True)
    name: str = Field(index=True, unique=True)
    permissions: list["Permission"] = Relationship(
        back_populates="roles",
        link_model=RolePermissionLink,
    )

class Permission(SQLModel, table=True):
    id: int = Field(primary_key=True)
    name: str = Field(index=True, unique=True)
    roles: list[Role] = Relationship(
        back_populates="permissions",
        link_model=RolePermissionLink,
    )

... then it works fine (no console output).

Footnotes

1. Full traceback at https://gist.github.com/ixycoexzckwpmlcu/75e0012542f39f8231f0b3c72e280ca4 ↩

[mockingjet]

Hi @ixycoexzckwpmlcu, thanks for testing. I have checked multiple times and my code is the same as yours. Can you share which database and which version of sqlmodel you used?

I am using postgres and sqlmodel@0.0.18

[mockingjet]

Ah... I read this and now I know I can only declare relationship in Table Model https://sqlmodel.tiangolo.com/tutorial/fastapi/teams/#relationship-attributes
I shouldve not put relationship field in BaseModel