将第二个数据库添加到 alembic 上下文中

我想在迁移过程中连接到第二个外部数据库，以将其部分数据移至本地数据库中。最好的方法是什么？

将第二个数据库添加到 alembic 上下文后（我不知道该怎么做），在迁移期间如何在数据库上运行 SQL 语句？

这就是我的env.py现在看起来像：

from alembic import context
from sqlalchemy import engine_from_config, pool
from logging.config import fileConfig
from migration_settings import database_url
import models

# 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
target_metadata = models.Base.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 = database_url or config.get_main_option("sqlalchemy.url")
    context.configure(url=url, target_metadata=target_metadata, literal_binds=True, version_table_schema='my_schema')

    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.
    """
    config_overrides = {'url': database_url} if database_url is not None else {}
    connectable = engine_from_config(
        config.get_section(config.config_ini_section),
        prefix='sqlalchemy.',
        poolclass=pool.NullPool, **config_overrides)

    with connectable.connect() as connection:
        context.configure(
            connection=connection,
            target_metadata=target_metadata,
            version_table_schema='my_schema'
        )

        connection.execute('CREATE SCHEMA IF NOT EXISTS my_schema')

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


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