Support discriminated union

[wholmen]

First Check

• [X] I added a very descriptive title to this issue.
• [X] I used the GitHub search to find a similar issue and didn't find it.
• [X] I searched the SQLModel documentation, with the integrated search.
• [X] I already searched in Google "How to X in SQLModel" and didn't find any information.
• [X] I already read and followed all the tutorial in the docs and didn't find an answer.
• [X] I already checked if it is not related to SQLModel but to Pydantic.
• [X] I already checked if it is not related to SQLModel but to SQLAlchemy.

Commit to Help

• [ ] I commit to help with one of those options 👆

Example Code

from typing import Literal, Union, Optional
from sqlmodel import SQLModel, Field


class Bar(SQLModel):
    class_type: Literal["bar"] = "bar"
    name: str


class Foo(SQLModel):
    class_type: Literal["foo"] = "foo"
    name: str
    id: Optional[int]


class FooBar(SQLModel, table=True):
    id: int = Field(default=None, primary_key=True)
    data: Union[Foo, Bar] = Field(discriminator="class_type")

Description

• No support for Pydantic 1.9's implementation of discriminated union

Wanted Solution

Would like to have support for discriminated union in SQLModel-classes

Wanted Code

from typing import Literal, Union, Optional
from sqlmodel import SQLModel, Field


class Bar(SQLModel):
    class_type: Literal["bar"] = "bar"
    name: str


class Foo(SQLModel):
    class_type: Literal["foo"] = "foo"
    name: str
    id: Optional[int]


class FooBar(SQLModel, table=True):
    id: int = Field(default=None, primary_key=True)
    data: Union[Foo, Bar] = Field(discriminator="class_type")

Alternatives

No response

Operating System

Linux

Operating System Details

No response

SQLModel Version

0.0.6

Python Version

3.10.4

Additional Context

Pydantic has added support for discrimated unions, something I use in my project with Pydantic + SQLAlchemy.

I want to switch to SQLModel, but cannot switch before discriminated unions