"""add composite indexes for performance

Revision ID: j0k1l2m3n4o5
Revises: i9j0k1l2m3n4
Create Date: 2026-06-02 15:00:00.000000

"""
from typing import Sequence, Union
from alembic import op

revision: str = 'j0k1l2m3n4o5'
down_revision: Union[str, None] = 'i9j0k1l2m3n4'
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    # FK 索引 — 每次状态检查都要按 OLT 查询设备
    op.create_index('ix_onu_devices_olt_id', 'onu_devices', ['olt_id'])
    # 复合索引 — Dashboard 按区域+学校聚合
    op.create_index('ix_onu_devices_region_school', 'onu_devices', ['region', 'school_name'])
    # FK 索引 — DeviceStatusHistory 按设备查最新状态（最频繁的查询）
    op.create_index('ix_device_status_history_onu_device_id_checked', 'device_status_history', ['onu_device_id', 'checked_at'])


def downgrade() -> None:
    op.drop_index('ix_device_status_history_onu_device_id_checked', table_name='device_status_history')
    op.drop_index('ix_onu_devices_region_school', table_name='onu_devices')
    op.drop_index('ix_onu_devices_olt_id', table_name='onu_devices')