在 Alembic 中更改列名称时，是否有一个配置可以在 env 中配置以正确迁移？

Question

我用alembic在flask中迁移数据库，好像alembic没有给出迁移数据的正确方法，它只是创建新列并删除旧列，导致数据可能会被丢弃，这是代码.

docker-compose -f docker-compose.yml run xxx python manage.py db migrate -m "change number into index"

migrations/versions/xxx.py

from alembic import op
import sqlalchemy as sa

def upgrade():
    # ### commands auto generated by Alembic - please adjust! ###
    op.add_column('news', sa.Column('index', sa.Integer(), nullable=True))
    op.drop_column('news', 'number')

migrations/env.py

from __future__ import with_statement

import logging
from logging.config import fileConfig

from sqlalchemy import engine_from_config
from sqlalchemy import pool

from alembic import context

# 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)
logger = logging.getLogger('alembic.env')

# add your model's MetaData object here
# for 'autogenerate' support
# from myapp import mymodel
# target_metadata = mymodel.Base.metadata
from flask import current_app
config.set_main_option(
    'sqlalchemy.url',
    str(current_app.extensions['migrate'].db.engine.url).replace('%', '%%'))
target_metadata = current_app.extensions['migrate'].db.metadata

# other values from the config, defined by the needs of env.py,
# can be acquired:
# my_important_option = config.get_main_option("my_important_option")
# ... etc.


def run_migrations_offline():
    """Run migrations in 'offline' mode.

    This configures the context with just a URL
    and not an Engine, though an Engine is acceptable
    here as well.  By skipping the Engine creation
    we don't even need a DBAPI to be available.

    Calls to context.execute() here emit the given string to the
    script output.

    """
    url = config.get_main_option("sqlalchemy.url")
    context.configure(
        url=url, target_metadata=target_metadata, literal_binds=True, compare_type=True
    )

    with context.begin_transaction():
        context.run_migrations()


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.zzzcomputing.com/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.')

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

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

        with context.begin_transaction():
            context.run_migrations()


if context.is_offline_mode():
    run_migrations_offline()
else:
    run_migrations_online()

在 env.py 中是否有一些配置可以使用 alter_column 这样的正确方法而不是这种方式来迁移？

我只关心特定的配置，而不是搜索通用配置来自动更正错误。

Answer 1

您可以使用 op.alter_column:

op.alter_column('table_name', 'old_column', nullable=False, new_column_name='new_column')

在 Alembic 中更改列名称时，是否有一个配置可以在 env 中配置以正确迁移？

Is there one configure to config in env to migrate correctly when changing column's name within Alembic?

python

sqlalchemy

alembic