"""初始关系表和约束；仅首版建表使用元数据，后续迁移须冻结具体增量操作。"""
from alembic import op
from app.domain.models import Base
revision = '0001_initial'
down_revision = None
branch_labels = None
depends_on = None

def upgrade():
    """新库建立全部业务约束；已有表的迁移禁止由 create_all 猜测。"""
    Base.metadata.create_all(op.get_bind())

def downgrade():
    """显式 downgrade base 会删除业务表，运行前必须备份数据库和上传目录。"""
    Base.metadata.drop_all(op.get_bind())