daniil-berg
commented
1 year ago First off, if you haven't already, I suggest reading this section of the docs. It addresses the issue of infinite recursion (among other things) that can easily happen, if you don't think carefully about what data you actually want to get.
Second, I assume you forgot to copy the table=True in your example models. Without those, you can't use the models for any database queries.
The cyclic dilemma
There are already quite a few issues around this topic of including relationships in such a way. I haven't looked deeply into the code for this yet. But as I understand it, it is not at all clear, how exactly you should tackle the problem of cyclical relationship graphs. Not that there aren't any theoretical solutions. It seems to be more of a question of what a "sensible" approach may look like. In the end, it would have to be up to the user to decide, when exactly to stop walking along the relationship graph.
The most straightforward solution, and the one used right now is to simply avoid the issue altogether and force the user to e.g. set up his own response models (not tables) with the desired nesting of sub-models. (See the section "What Data to Include" on the aforementioned docs page.)
Be explicit yourself
So I would suggest closely following the advice about model inheritance from the docs for now. That means for your desired output:
from typing import List, Optional
from fastapi import FastAPI, Depends
from sqlmodel import Field, Relationship, Session, SQLModel, create_engine, select
class TeamBase(SQLModel):
name: str = Field(index=True)
...
class Team(TeamBase, table=True):
id: Optional[int] = Field(default=None, primary_key=True)
heroes: List["Hero"] = Relationship(back_populates="team")
class TeamRead(TeamBase):
id: int
class HeroBase(SQLModel):
name: str = Field(index=True)
...
team_id: Optional[int] = Field(default=None, foreign_key="team.id")
class Hero(HeroBase, table=True):
id: Optional[int] = Field(default=None, primary_key=True)
team: Optional[Team] = Relationship(back_populates="heroes")
class HeroRead(HeroBase):
id: int
class TeamReadWithHeroes(TeamRead):
heroes: List[HeroRead] = []
app = FastAPI()
sqlite_url = "sqlite:///test.db"
engine = create_engine(sqlite_url, echo=True)
def create_db_and_tables():
SQLModel.metadata.create_all(engine)
def get_session():
with Session(engine) as session:
yield session
@app.on_event("startup")
def on_startup():
create_db_and_tables()
@app.get("/teams/", response_model=List[TeamReadWithHeroes])
def get_teams(*, session: Session = Depends(get_session)) -> List[Team]:
return session.exec(select(Team)).all()Under the hood, FastAPI will basically call the TeamReadWithHeroes.from_orm() method on each Team instance returned by the database query. This will populate the heroes field on that model and give you the desired result:
[
{
"name": "theteam",
"id": 1,
"heroes": [
{
"name": "foo",
"team_id": 1,
"id": 1
},
{
"name": "bar",
"team_id": 1,
"id": 2
}
]
}
]
busykoala
antont
xavipolo
First Check
Commit to Help
Example Code
Description
When returning a list of Teams the
Relationshipfields are not covered in the output. I believe the response is usingpydantic.main.BaseModel.json()to get the data (and there it will only cover non-Relationshipfields).It would be great if there was an option to also return the
Relationshipfields especially if{"lazy": "selectin"}was enabled for the relation. It's an easy workaround to walk the objects and return the complete data as json in the endpoint, but since we already have the models that is not very satisfying (also because the response_model for openapi will not be easily achievable).Did I miss an option to enable having the
Relationshipattributes in the response, or is that something that could be worked on? I would also be happy to contribute but would need a pointer on where to start.Operating System
Linux
Operating System Details
No response
SQLModel Version
0.0.7
Python Version
3.10.4
Additional Context
No response