Alembic - sqlalchemy不检测现有表

Question

我问了一个关于如何使用Alembic - sqlalchemy initial migration检测表的问题

target_metadata = Base.metadata

为

alembic revision --autogenerate -m "initial migration"

在我将我的模型导入到env.py文件后，它看起来工作得很好，但它并没有检测到实际存在的表，所以它创建了一个包含所有表的迁移文件，例如：

def upgrade():
    ### commands auto generated by Alembic - please adjust! ###
    op.create_table('Brand',
    sa.Column('id', sa.Integer(), nullable=False),
    sa.Column('name', sa.String(), nullable=True),
    sa.Column('slug', sa.String(), nullable=True),
    sa.Column('date_created', sa.DateTime(), nullable=True),
    sa.Column('date_updated', sa.DateTime(), nullable=True),
    sa.PrimaryKeyConstraint('id'),
    schema='Products'
    )

def downgrade():
    ### commands auto generated by Alembic - please adjust! ###
    op.drop_table('ProductFile', schema='Products')

我试过了：

alembic stamp head

但在运行该命令并运行autogenerate命令后，系统将再次生成所有模型。

from project.apps.users.models import *
from project.apps.orders.models import *
from project.apps.products.models import *

from project.base import Base, metadata

# this is the Alembic Config object, which provides
# access to the values within the .ini file in use.
config = context.config

# Interpret the config file for Python logging.
# This line sets up loggers basically.
fileConfig(config.config_file_name)

# add your model's MetaData object here
# for 'autogenerate' support
# from myapp import mymodel
target_metadata = Base.metadata

我该如何避免这个问题呢？

编辑：

ENV.py：

https://gist.github.com/pypetey/bb65807ce773d8baeaf1

我删除了db并运行了一个迁移。

(env) D:\projekty\test>alembic revision --autogenerate
INFO  [alembic.migration] Context impl MSSQLImpl.
INFO  [alembic.migration] Will assume transactional DDL.
INFO  [alembic.autogenerate.compare] Detected added table u'Users.Country'
INFO  [alembic.autogenerate.compare] Detected added table u'Products.Brand'
INFO  [alembic.autogenerate.compare] Detected added table u'Users.User'
INFO  [alembic.autogenerate.compare] Detected added table u'Products.Product'
INFO  [alembic.autogenerate.compare] Detected added table u'Products.ProductFile
'
INFO  [alembic.autogenerate.compare] Detected added table u'Orders.Order'
INFO  [alembic.autogenerate.compare] Detected added table u'Products.Category'
INFO  [alembic.autogenerate.compare] Detected added table u'Products.Review'
INFO  [alembic.autogenerate.compare] Detected added table u'Users.UserAddress'
INFO  [alembic.autogenerate.compare] Detected added table u'Orders.OrderItem'
INFO  [alembic.autogenerate.compare] Detected added table u'Orders.OrderStatus'
Generating D:\projekty\test\alembic\versions\1c6337c144a7_.py ... done

(env) D:\projekty\test>alembic upgrade head
INFO  [alembic.migration] Context impl MSSQLImpl.
INFO  [alembic.migration] Will assume transactional DDL.
INFO  [alembic.migration] Running upgrade None -> 1c6337c144a7, empty message

(env) D:\projekty\test>alembic revision --autogenerate
INFO  [alembic.migration] Context impl MSSQLImpl.
INFO  [alembic.migration] Will assume transactional DDL.
INFO  [alembic.autogenerate.compare] Detected added table u'Users.Country'
INFO  [alembic.autogenerate.compare] Detected added table u'Products.Brand'
INFO  [alembic.autogenerate.compare] Detected added table u'Users.User'
INFO  [alembic.autogenerate.compare] Detected added table u'Products.Product'
INFO  [alembic.autogenerate.compare] Detected added table u'Products.ProductFile
'
INFO  [alembic.autogenerate.compare] Detected added table u'Orders.Order'
INFO  [alembic.autogenerate.compare] Detected added table u'Products.Category'
INFO  [alembic.autogenerate.compare] Detected added table u'Products.Review'
INFO  [alembic.autogenerate.compare] Detected added table u'Users.UserAddress'
INFO  [alembic.autogenerate.compare] Detected added table u'Orders.OrderItem'
INFO  [alembic.autogenerate.compare] Detected added table u'Orders.OrderStatus'
Generating D:\projekty\test\alembic\versions\5abb204549f_.py ... done

Answer 1

我也有同样的问题--我不知道它是否仍然影响着你。对我来说，这个问题是因为我使用的模式不是默认的-我认为同样的事情也发生在您身上，因为您使用的是"Products“模式。我在以下位置发布了一期：

https://bitbucket.org/zzzeek/alembic/issue/281/autogenerate-fails-to-detect-existing

在一些指导下，通过在alembic/env.py模块的两个run_migrations_*函数中设置include_schemas=True，设法解决了这个问题。

请参阅docs

如果为True，则autogenerate将扫描由SQLAlchemy get_schema_names()方法定位的所有架构，并包括在所有这些架构中找到的表中的所有差异。在使用此选项时，您可能还希望使用EnvironmentContext.configure.include_object选项来指定一个可调用对象，该可调用对象可以过滤所包含的表/模式。

Answer 2

我有一个观察。

在alembic中导入到env.py的元数据必须具有所有模型元数据。因此，在调用Base之前，必须加载所有模型。所以,

db_setup.py将会有

...
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
...

而models.py将会有

from .db_setup import Base
from sqlalchemy import Column, String
class TestModel(Base):
    __tablename__ = "test"
    field_1 = Column(String)
    ...

现在，在main.py中

from flask import Flask
...
from models.setup import Base
app = Flask(__name__)
...

最后，在alembic env.py中，

...
...
from main import Base # Not from db_setup!
target_metadata = Base.metadata
...
...