CrudRouter Lazy loading support

[davidgfr]

Hello,
I would like to know if there is a way to have "lazy loading" using crudrouter on fastapi?
Is there a solution or a manner to do it?
Thank you in advance.

[awtkns]

Hi There. So by default I believe it supports lazy loading. It all depends on how you've set up your database models, your pydantic models, and your ORM. None of the "lazy loading" is handled by crudrouter but rather your ORM

[davidgfr]

Hi, thank you for your answer. I will see that and let you know ;). But I think I had tried to do it with pydantic models and the orm but no way to have the lazy loading. I will try again many ways!

[davidgfr]

Hi @awtkns, could you please how to setup database models, pydantic models and orm to have "lazy loading", I tried to find a solution but no way to do that!
"Normal lazy loading" is working but how to do that when I use crudrouter?
Thank you in advance for your help!

[awtkns]

HI @davidgfr below is a full example with sqlalchemy lazy loading

from typing import List

from pydantic import BaseModel
from sqlalchemy import Column, Integer, ForeignKey
from sqlalchemy.orm import relationship
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker
from fastapi import Fastapi
from fastapi_crudrouter import SQLAlchemyCRUDRouter

 app = FastAPI()

 engine = create_engine(SQLALCHEMY_DATABASE_URL, connect_args={"check_same_thread": False})
 SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
 Base = declarative_base()

 def session():
     session = SessionLocal()
     try:
         yield session
         session.commit()
     finally:
         session.close()

class ORMModel(BaseModel):
    id: int

    class Config:
        orm_mode = True

class ChildSchema(ORMModel):
    parent_id: int

class ParentSchema(ORMModel):
    children: List[ChildSchema] = []

class ParentCreate(ORMModel):
    pass

class Child(Base):
    __tablename__ = 'child'
    id = Column(Integer, primary_key=True, index=True)
    parent_id = Column(Integer, ForeignKey('parent.id'))

class Parent(Base):
    __tablename__ = 'parent'
    id = Column(Integer, primary_key=True, index=True)

    children = relationship(Child, backref='parent', lazy='joined')


Base.metadata.create_all(bind=engine)
parent_router = SQLAlchemyCRUDRouter(schema=ParentSchema, create_schema=ParentCreate, db_model=Parent, db=session)
child_router = SQLAlchemyCRUDRouter(schema=ChildSchema, db_model=Child, db=session)
app.include_router(parent_router)
app.include_router(child_router)

When you go to the /parent route the parents childern will also be returned assuming the parent ask children. Is this what you were referring to?

[awtkns]

@davidgfr good to close this now?

[davidgfr]

Hi @awtkns , I will check this and let you know before closing the issue! Thank you!