Alembic初学者在这里。我遇到了Alembic试图删除已经创建的表的一些问题。我不知道发生了什么事。现在我有一个如下所示的数据库:
如果我运行alembic upgrade head
,我会将此作为结果:
INFO [alembic.runtime.migration] Context impl PostgresqlImpl.
INFO [alembic.runtime.migration] Will assume transactional DDL.
如果我运行alembic history
,我会得到这个结果,这是正确的:
c2659db918a9 -> 765c30f7078c (head), creat table views
c4a0cac54f89 -> c2659db918a9, Made last_update not null for all tables
19dd9f3d1d16 -> c4a0cac54f89, Added last_update field defaulted to now
77c03ebb393b -> 19dd9f3d1d16, Added indexes to each table
0737825277d8 -> 77c03ebb393b, Change foreign key columns to non-nullable
5eb3c5f7f599 -> 0737825277d8, Rename a column in daily_etf_underlying table
0da0b2a43172 -> 5eb3c5f7f599, Add extra_info column to daily_etf_underlying
c181fe8bcfa9 -> 0da0b2a43172, Make daily_etf id columns nullable
8fba2675104b -> c181fe8bcfa9, added fixing table
074563d69c3b -> 8fba2675104b, Modify daily_etf tables
2c9de57e43f0 -> 074563d69c3b, Add fund_family columns
80de6fb0a104 -> 2c9de57e43f0, Modify daily_etf table
a970af9bb117 -> 80de6fb0a104, Add daily_etf_basket, daily_etf_fx_forward tables
<base> -> a970af9bb117, Add daily_etf table
但如果我跑alembic revision --autogenerate -m "<>"
,我就会得到这个!
alembic revision --autogenerate -m "Raw fidessa client trade table"
INFO [alembic.runtime.migration] Context impl PostgresqlImpl.
INFO [alembic.runtime.migration] Will assume transactional DDL.
INFO [alembic.ddl.postgresql] Detected sequence named 'daily_etf_fx_forward_id_seq' as owned by integer column 'daily_etf_fx_forward(id)', assuming SERIAL and omitting
INFO [alembic.autogenerate.compare] Detected removed table 'daily_etf_fx_forward'
INFO [alembic.autogenerate.compare] Detected removed table 'daily_etf'
INFO [alembic.ddl.postgresql] Detected sequence named 'daily_fx_fixing_rate_id_seq' as owned by integer column 'daily_fx_fixing_rate(id)', assuming SERIAL and omitting
INFO [alembic.autogenerate.compare] Detected removed table 'daily_fx_fixing_rate'
INFO [alembic.ddl.postgresql] Detected sequence named 'daily_etf_underlying_id_seq' as owned by integer column 'daily_etf_underlying(id)', assuming SERIAL and omitting
INFO [alembic.autogenerate.compare] Detected removed table 'daily_etf_underlying'
Generating C:\dev\Projects\stark_database\stark_database\migrations\versions\86174c06e59e_raw_fidessa_client_trade_table.py ... done
我的自动生成的文件只是试图删除我的所有表:(
def upgrade():
# ### commands auto generated by Alembic - please adjust! ###
op.drop_table('daily_fx_fixing_rate')
op.drop_table('daily_etf_underlying')
op.drop_table('daily_etf')
op.drop_table('daily_etf_fx_forward')
# ### end Alembic commands ###
这里发生了什么?为什么alembic试图删除所有内容?
感谢您的帮助。
编辑:alembic.ini
:
[alembic]
script_location = migrations
sqlalchemy.url = postgresql://stark_admin:hpt@localhost/stark
env.py
正是alembic init alembic
答案 0 :(得分:4)
metadata
对象不正确。
对于那些阅读,
确保metadata
中有正确的target_metadata = metadata
。如果您已在数据库中有一些表,并且您提供了新的metadata
或None
元数据,正如Ilja在评论中建议的那样,您将看到此行为,因为alembic根据该元数据知道这些表不应该在数据库中,所以它会尝试删除那些。
此外,通常您会在SQLAlchemy
的不同文件中使用类。为此,您必须确保在文件中使用相同的metadata
或Base
实例。否则,您将获得不检测表或尝试删除现有表的这种行为。
以下是后一种情况的一个例子:
假设我有一个类似
的结构database
/migrations
/versions
1348ht31r3_first_migration.py
env.py
README
script.py.mako
/models
__init__.py
a_class.py
在__init__.py
中,我会执行典型的declarative_base()
:
# __init__.py
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
engine = create_engine('url')
然后在a_class.py
中,我的模型类的父类是来自__init__.py
from datetime import datetime
from sqlalchemy import Column, Integer, String, Float
from sqlalchemy import Date, DateTime
from sqlalchemy import ForeignKey
from sqlalchemy.dialects.postgresql import JSONB
from sqlalchemy.orm import relationship
from stark_database.models import Base
class AClass(Base):
__tablename__ = 'a_class'
id = Column(Integer, primary_key=True)
insert_date = Column(Date)
symbol = Column(String)
pnu = Column(Float)
projected_shares_outstanding = Column(Float)
shares_outstanding = Column(Float)
projected_nav = Column(Float)
nav = Column(Float)
basket_cash_per_currency = Column(JSONB)
fund_cash_per_currency = Column(JSONB)
info_type = Column(String)
fund_family = Column(String)
last_updated = Column(DateTime, nullable=False, default=datetime.now, onupdate=datetime.now)
这是正确的,但在env.py
中,您必须确保导入基类和模型。
from __future__ import with_statement
import os
import sys
from logging.config import fileConfig
from alembic import context
from sqlalchemy import engine_from_config, pool
# DO NOT DELETE THIS LINE.
from database.models import Base, a_class
这不是一个alembic
的东西,但在我看来它有点像python。
希望这有帮助。