PostgreSQL 未填充异步（FastAPI）

Question

我对 FastAPI 比较陌生，我正在尝试创建一个类，该类具有单个表，一旦服务器开始使用，该表就会填充数据：

uvicorn main:app --reload

我一直在努力使其工作并连续几个小时进行故障排除，但此时我真的很感激一些建议。

这是我到目前为止的代码：

from fastapi import FastAPI, HTTPException, Depends
from pydantic import BaseModel
from typing import List, Annotated
from sqlalchemy.orm import Session
from sqlalchemy import Column, Integer, String, text
from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession
from sqlalchemy.orm import sessionmaker, declarative_base
from contextlib import asynccontextmanager

DATABASE_URL = "postgresql+asyncpg://$DB_USER:$DB_PWD@$DB_SERVER/$DB_NAME"

Base = declarative_base()

class Person(Base):
    __tablename__ = "persons"
    id = Column(Integer, primary_key=True, index=True)
    name = Column(String, index=True)
    age = Column(Integer)
    
engine = create_async_engine(DATABASE_URL, future=True, echo=True)

SessionLocal = sessionmaker(bind=engine, class_=AsyncSession, expire_on_commit=False)

app = FastAPI()
@asynccontextmanager
async def lifespan(app: FastAPI):
    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)
        await seed_database(conn)
    
    yield 
    await engine.dispose()

app.lifespan_context = lifespan

async def seed_database(conn):
    await conn.execute(text("INSERT INTO persons (name, age) VALUES ('Alice', 23)"))
    await conn.execute(text("INSERT INTO persons (name, age) VALUES ('Bob', 22)"))
    await conn.commit()
    print("Database seeded with initial persons.")

@app.get("/")
async def read_root(db: AsyncSession = Depends(lambda: SessionLocal())):
    result = await db.execute(text("SELECT * FROM persons"))
    persons = result.mappings().all()
    return {"persons": persons}

我尝试切换代码并执行一些解决方法，但由于某种原因我无法让它工作..

Answer 1

您在 Depends() 中使用 SessionLocal()，它们不是为异步会话设计的。尝试如下操作：

async def get_db():
    async with SessionLocal() as session:
        yield session

async def read_root(db: AsyncSession = Depends(get_db)):