dingdanquanliucheng/backend/migrations/env.py

"""Alembic 数据库迁移环境配置。

配置迁移工具的数据库连接、元数据目标和迁移执行方式。
支持在线迁移（连接数据库执行）和离线迁移（生成 SQL 脚本）。
"""

from logging.config import fileConfig
from pathlib import Path
import sys

from alembic import context
from sqlalchemy import engine_from_config, pool

# 确保项目根目录在 sys.path 中，使 backend 包可被导入
PROJECT_ROOT = Path(__file__).resolve().parents[2]
if str(PROJECT_ROOT) not in sys.path:
    sys.path.insert(0, str(PROJECT_ROOT))

from backend.app.db import Base, build_database_url
from backend.app.models import *  # noqa: F401,F403

config = context.config
config.set_main_option("sqlalchemy.url", build_database_url())

if config.config_file_name is not None:
    fileConfig(config.config_file_name)

# 元数据用于 autogenerate 模式自动检测模型变更
target_metadata = Base.metadata


def run_migrations_offline() -> None:
    """离线模式执行迁移，生成 SQL 脚本而不连接数据库。"""
    url = config.get_main_option("sqlalchemy.url")
    context.configure(url=url, target_metadata=target_metadata, literal_binds=True)

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


def run_migrations_online() -> None:
    """在线模式执行迁移，直接连接数据库执行 DDL 变更。"""
    connectable = engine_from_config(
        config.get_section(config.config_ini_section, {}),
        prefix="sqlalchemy.",
        poolclass=pool.NullPool,
    )

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

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


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