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Support discriminated union #356
Description
First Check
- I added a very descriptive title to this issue.
- I used the GitHub search to find a similar issue and didn't find it.
- I searched the SQLModel documentation, with the integrated search.
- I already searched in Google "How to X in SQLModel" and didn't find any information.
- I already read and followed all the tutorial in the docs and didn't find an answer.
- I already checked if it is not related to SQLModel but to Pydantic.
- 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
Activity
ljluestc commentedon Sep 3, 2023
from sqlmodel import SQLModel, Field, Relationship
from typing import Optional
class Base(SQLModel, table=True):
id: Optional[int] = Field(default=None, primary_key=True)
class_type: str
class Bar(Base):
mapper_args = {"polymorphic_identity": "bar"}
name: str
class Foo(Base):
mapper_args = {"polymorphic_identity": "foo"}
name: str
class FooBar(SQLModel, table=True):
id: int = Field(default=None, primary_key=True)
data: Relationship[Base] = Field(discriminator="class_type")
Create instances of Bar and Foo
bar_instance = Bar(name="My Bar")
foo_instance = Foo(name="My Foo")
Create instance of FooBar with either a Bar or Foo instance
foobar_instance = FooBar(data=bar_instance) # Or Foo instance
print(bar_instance)
print(foo_instance)
print(foobar_instance)
tiangolo commentedon Oct 26, 2023
Support for this was added in #440
You will be able to use it in the next version:
0.0.10🎉github-actions commentedon Nov 6, 2023
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.
stuartaxonHO commentedon Dec 4, 2025
YuriiMotov commentedon Dec 4, 2025
stuartaxonHO commentedon Dec 4, 2025
stuartaxonHO commentedon Dec 4, 2025