Python 为什么我的表名在某些情况下会被调用两次，而在其他情况下不会被调用？FastAPI，SQLAlchemy

我使用的是类似烧瓶的FastAPI。我有两个不同的页面，一个功能完全正常，另一个提供以下内容：

INFO:     127.0.0.1:57256 - "GET /companies?month=4&year=2020&day=5 HTTP/1.1" 500 Internal Server Error
ERROR:    Exception in ASGI application
Traceback (most recent call last):
  File "c:\users\admin\google~1\python\new_co~1\env\lib\site-packages\uvicorn\protocols\http\h11_impl.py", line 384, in run_asgi
    result = await app(self.scope, self.receive, self.send)
  File "c:\users\admin\google~1\python\new_co~1\env\lib\site-packages\uvicorn\middleware\proxy_headers.py", line 45, in __call__
    return await self.app(scope, receive, send)
  File "c:\users\admin\google~1\python\new_co~1\env\lib\site-packages\fastapi\applications.py", line 149, in __call__
    await super().__call__(scope, receive, send)
  File "c:\users\admin\google~1\python\new_co~1\env\lib\site-packages\starlette\applications.py", line 102, in __call__
    await self.middleware_stack(scope, receive, send)
  File "c:\users\admin\google~1\python\new_co~1\env\lib\site-packages\starlette\middleware\errors.py", line 181, in __call__
    raise exc from None
  File "c:\users\admin\google~1\python\new_co~1\env\lib\site-packages\starlette\middleware\errors.py", line 159, in __call__
    await self.app(scope, receive, _send)
  File "c:\users\admin\google~1\python\new_co~1\env\lib\site-packages\starlette\exceptions.py", line 82, in __call__
    raise exc from None
  File "c:\users\admin\google~1\python\new_co~1\env\lib\site-packages\starlette\exceptions.py", line 71, in __call__
    await self.app(scope, receive, sender)
  File "c:\users\admin\google~1\python\new_co~1\env\lib\site-packages\starlette\routing.py", line 550, in __call__
    await route.handle(scope, receive, send)
  File "c:\users\admin\google~1\python\new_co~1\env\lib\site-packages\starlette\routing.py", line 227, in handle
    await self.app(scope, receive, send)
  File "c:\users\admin\google~1\python\new_co~1\env\lib\site-packages\starlette\routing.py", line 41, in app
    response = await func(request)
  File "c:\users\admin\google~1\python\new_co~1\env\lib\site-packages\fastapi\routing.py", line 196, in app
    raw_response = await run_endpoint_function(
  File "c:\users\admin\google~1\python\new_co~1\env\lib\site-packages\fastapi\routing.py", line 150, in run_endpoint_function
    return await run_in_threadpool(dependant.call, **values)
  File "c:\users\admin\google~1\python\new_co~1\env\lib\site-packages\starlette\concurrency.py", line 34, in run_in_threadpool
    return await loop.run_in_executor(None, func, *args)
  File "c:\users\admin\appdata\local\programs\python\python38-32\Lib\concurrent\futures\thread.py", line 57, in run
    result = self.fn(*self.args, **self.kwargs)
  File ".\main.py", line 73, in get_companies
    return myquery.all()
  File "c:\users\admin\google~1\python\new_co~1\env\lib\site-packages\sqlalchemy\orm\query.py", line 3246, in all
    return list(self)
  File "c:\users\admin\google~1\python\new_co~1\env\lib\site-packages\sqlalchemy\orm\query.py", line 3405, in __iter__
    return self._execute_and_instances(context)
  File "c:\users\admin\google~1\python\new_co~1\env\lib\site-packages\sqlalchemy\orm\query.py", line 3430, in _execute_and_instances
    result = conn.execute(querycontext.statement, self._params)
  File "c:\users\admin\google~1\python\new_co~1\env\lib\site-packages\sqlalchemy\engine\base.py", line 984, in execute
    return meth(self, multiparams, params)
  File "c:\users\admin\google~1\python\new_co~1\env\lib\site-packages\sqlalchemy\sql\elements.py", line 293, in _execute_on_connection
    return connection._execute_clauseelement(self, multiparams, params)
  File "c:\users\admin\google~1\python\new_co~1\env\lib\site-packages\sqlalchemy\engine\base.py", line 1097, in _execute_clauseelement
    ret = self._execute_context(
  File "c:\users\admin\google~1\python\new_co~1\env\lib\site-packages\sqlalchemy\engine\base.py", line 1287, in _execute_context
    self._handle_dbapi_exception(
  File "c:\users\admin\google~1\python\new_co~1\env\lib\site-packages\sqlalchemy\engine\base.py", line 1481, in _handle_dbapi_exception
    util.raise_(
  File "c:\users\admin\google~1\python\new_co~1\env\lib\site-packages\sqlalchemy\util\compat.py", line 178, in raise_
    raise exception
  File "c:\users\admin\google~1\python\new_co~1\env\lib\site-packages\sqlalchemy\engine\base.py", line 1247, in _execute_context
    self.dialect.do_execute(
  File "c:\users\admin\google~1\python\new_co~1\env\lib\site-packages\sqlalchemy\engine\default.py", line 590, in do_execute
    cursor.execute(statement, parameters)
sqlalchemy.exc.ProgrammingError: (psycopg2.errors.DuplicateAlias) table name "companies" specified more than once

[SQL: SELECT companies.record_created AS companies_record_created, companies.number AS companies_number, companies.name AS companies_name, companies.incorporated AS companies_incorporated
FROM companies, companies
WHERE EXTRACT(year FROM companies.incorporated) = %(param_1)s AND EXTRACT(month FROM companies.incorporated) = %(param_2)s AND EXTRACT(day FROM companies.incorporated) = %(param_3)s]
[parameters: {'param_1': 2020, 'param_2': 4, 'param_3': 5}]
(Background on this error at: http://sqlalche.me/e/f405)

因此，错误的关键是由于未知原因，表名被生成了两次

sqlalchemy.exc.ProgrammingError: (psycopg2.errors.DuplicateAlias) table name "companies" specified more than once

我可以在这里看到：

FROM companies, companies

这只会发生在一个版本中，而不会发生在另一个版本中（？）

现在让我给你看一个完全好用的东西

# main.py
# various imports

...


@app.get("/incorporated/today")
def read_cos_today(skip: int = 0, limit: int = 100, db: Session = Depends(get_db)):
    today = datetime.datetime.now()
    return crud.get_company_by_date(db, year=today.year, month=today.month, day=today.day).all()

上述方法工作正常，并返回预期的json

然而，下面给出了前面提到的错误

# main.py
# various imports

...


@app.get("/companies", response_model=List[schemas.Company])
def get_companies(
    year: int = None, month: int = None, day: int = None, number: int = None, 
    name: str = None, db: Session = Depends(get_db)):
    arguments = locals()
    arguments.pop("db")
    if not any(arguments.values()):
        return None
    myquery = db.query(models.Company)
    for key, value in arguments.items():
        if not value:
            continue
        if key == 'year' or key == 'month' or key == 'day':
            myquery = crud.get_company_by_date(db, query=myquery, **{key:value})
        else:
            myquery = crud.filter_query(myquery, **{key:value})
    return myquery.all()

下面是

crud.py

# crud.py
# various imports

...


def filter_query(query: Query, **kwargs):
    """Filter an input query for the given kwargs.

    Args:
        query (Query): An existing query from the database.
        **kwargs: A column from the database.

    Returns:
        query (Query): The filtered query.
    """

    for key,value in kwargs.items():
        query = query.filter_by(**{key:value})
    return query


def get_company_by_date(session: Session, query: Query = None, **kwargs):
    """Return an ordered Company query object filtered by date.

    Args:
        session (Session): A session connected to the database.
        query (Query): An existing query from the database.
        **kwargs: year, month or day (int).

    Returns:
        query (Query): A query result filtered by the input kwargs.
    """

    if not query:
        query = session.query(models.Company)
    for key, value in kwargs.items():
        print("Do the thing here yes")
        query = query.filter(extract(key, models.Company.incorporated)==value)
    return query

这让我有点发疯。我不明白为什么它会在这里复制表名。即使我做了一个简单的

http://127.0.0.1:8000/companies?month=4

这会引发错误，因此推测这不是链接方式的问题（？）

---

请帮助我理解我做错了什么。

呸。显然，将现有查询传递到

crud.get\u company\u by\u date

是导致问题的原因

在

main.py

中，我将

get_companys

函数编辑为以下内容（因为问题似乎在于链接

get_company\u by_date

函数）：

---

似乎有两个独立的类

模型。Company

，一个是由

get_companys

看到的，另一个是由

get_Company\u by_date

看到的。如果你说的是

模式。Company

和

模型。Company

是设计的，是FastAPI分离前端和后端方式的一部分。不，不是模式，但是

models.Company

。该行为与该类有2个实例的情况相匹配。

@app.get("/companies", response_model=List[schemas.Company])
def get_companies(
    year: int = None, month: int = None, day: int = None, number: int = None, 
    name: str = None, db: Session = Depends(get_db)):

    arguments = locals()
    arguments.pop("db")

    if not any(arguments.values()):
        return None

    myquery = db.query(models.Company)
    datedict = {}

    for key, value in arguments.items():
        if key == "number" and datedict:
            myquery = crud.get_company_by_date(db, **datedict)

        if not value:
            continue

        if key == 'year' or key == 'month' or key == 'day':
            datedict[key] = value
        else:
            myquery = crud.filter_query(myquery, **{key:value})

    return myquery.all()