SQLAlchemy alembic AmbiguousForeignKeysError 用于声明类型但不用于等效的非声明类型

Question

我有以下 alembic 迁移：

revision = '535f7a49839'
down_revision = '46c675c68f4'

from alembic import op
import sqlalchemy as sa
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker
from datetime import datetime

Session = sessionmaker()
Base = declarative_base()

metadata = sa.MetaData()

# This table definition works
organisations = sa.Table(
    'organisations',
    metadata,
    sa.Column('id', sa.Integer, primary_key=True),
    sa.Column('creator_id', sa.Integer),
    sa.Column('creator_staff_member_id', sa.Integer),
)

"""
# This doesn't...
class organisations(Base):
    __tablename__ = 'organisations'
    id = sa.Column(sa.Integer, primary_key=True)
    creator_id = sa.Column(sa.Integer)
    creator_staff_member_id = sa.Column(sa.Integer)
"""


def upgrade():
    bind = op.get_bind()
    session = Session(bind=bind)
    session._model_changes = {} # if you are using Flask-SQLAlchemy, this works around a bug
    print(session.query(organisations).all())
    raise Exception("don't succeed")


def downgrade():
    pass

现在，当我使用命令式定义的 table（未注释掉的那个）时，查询 session.query(organisations).all() 有效。但是，如果我使用声明式版本（据我所知应该是等效的），则会出现错误：

sqlalchemy.exc.AmbiguousForeignKeysError: Could not determine join condition between parent/child tables on relationship StaffMember.organisation - there are multiple foreign key paths linking the tables. Specify the 'foreign_keys' argument, providing a list of those columns which should be counted as containing a foreign key reference to the parent table.

现在我明白这个错误的意思了：我的 实际模型 中有两个从 organisations 到 staff_members 的外键。但是为什么 alembic 关心这些，它怎么知道它们的存在呢？此迁移如何知道存在名为 StaffMember 的东西？据我所知，alembic 应该只知道你在迁移中明确告诉它的模型。

Answer 1

原来问题出在我用来调用 alembic 的 Flask-script 设置上。我用来调用 alembic 的命令是导入代码来初始化我的 Flask 应用程序，它本身正在导入我的实际模型。

SQLAlchemy alembic AmbiguousForeignKeysError 用于声明类型但不用于等效的非声明类型

SQLAlchemy alembic AmbiguousForeignKeysError for declarative type but not for equivalent non-declarative type

python

sqlalchemy

alembic