Flask-migrate和更改列类型

Question

我正在尝试学习一些Flask,我正在使用Flask-Migrate 1.6.0

所以我制作了一个看起来像这样的模型

class Download(db.Model):

__tablename__ = "downloads"

id = db.Column(db.Integer, autoincrement=True, primary_key=True)
filename = db.Column(db.String, nullable=False)
size = db.Column(db.Integer, nullable=False)
location = db.Column(db.String, nullable=False)
season = db.Column(db.Integer, nullable=False)
download_timestamp = db.Column(db.DateTime, nullable=False)

show_id = db.Column(db.Integer, ForeignKey("shows.id"))

def __init__(self,filename,size,location,timestamp,season):
    self.filename = filename
    self.size = size
    self.location = location
    self.download_timestamp = timestamp
    self.season = season

def __repr__(self):
    return '<File {}'.format(self.filename)

然后我将它更改为完全相同的东西,除了这一行:

size = db.Column(db.BigInteger, nullable=False)

当我跑我的

manager.py db migrate

命令它不会检测列类型的更改.我已经阅读了它,我知道它应该在我更改env.py并添加compare_type = True变量时将其取出.但我这样做无济于事,这个方法现在看起来像这样

def run_migrations_online():
"""Run migrations in 'online' mode.

In this scenario we need to create an Engine
and associate a connection with the context.

"""

# this callback is used to prevent an auto-migration from being generated
# when there are no changes to the schema
# reference: http://alembic.readthedocs.org/en/latest/cookbook.html
def process_revision_directives(context, revision, directives):
    if getattr(config.cmd_opts, 'autogenerate', False):
        script = directives[0]
        if script.upgrade_ops.is_empty():
            directives[:] = []
            logger.info('No changes in schema detected.')

engine = engine_from_config(config.get_section(config.config_ini_section),
                            prefix='sqlalchemy.',
                            poolclass=pool.NullPool)

connection = engine.connect()
context.configure(connection=connection,
                  target_metadata=target_metadata,
                  compare_type=True,
                  process_revision_directives=process_revision_directives,
                  **current_app.extensions['migrate'].configure_args)

try:
    with context.begin_transaction():
        context.run_migrations()
finally:
    connection.close()

好的,我的问题是:

我在更改env.py文件时做错了什么？

如果我没有,它仍然没有接受它,我如何完全手动进行下一次迁移修订？因为我的migrate文件夹中的修订版具有如下所示的名称,并且其中的内容就像这样

# revision identifiers, used by Alembic.
revision = '7e9f264b0f'
down_revision = '2e59d536f50'

我想我可以复制一个,组成一个名字..但是下一个由烧瓶迁移的人会认出它吗？所以是的..没有太多的黑客攻击,处理它的正确方法是什么？

Answer 1

只需在Migrate构造函数中添加compare_type = True即可

from flask_migrate import Migrate
migrate = Migrate(compare_type=True)

app = Flask(__name__)
migrate.init_app(app)

Answer 2

默认情况下,自动生成修订时,Alembic无法识别列类型更改等内容.进行这些更细化的更改时,您需要手动修改迁移以包含这些更改

例如,在您的迁移文件中

from alembic import op
import sqlalchemy as sa
def upgrade():
    # ...
    op.alter_column('downloads', 'size', existing_type=sa.Integer(), type_=sa.BigInteger())
def downgrade():
    # ...
    op.alter_column('downloads', 'size', existing_type=sa.BigInteger(), type_=sa.Integer())

有关操作的详细信息,请参阅操作参考

您可以通过修改您的env.py和alembic.ini打开检测方式的变化,看到这里

Answer 3

默认情况下，Flask-migrate 不会在列类型更改时跟踪更改。实现这一目标的众多方法之一是设置

比较类型=真

在env.py 下。例如——

context.configure(connection=connection,
                      target_metadata=target_metadata,
                      process_revision_directives=process_revision_directives,
                      compare_type=True,
                      **current_app.extensions['migrate'].configure_args)