"""message 补 (channel, owner_account_id, timestamp) 索引(客户列表 7.7s 回归修复)

Revision ID: c53f90b1e6a4
Revises: b41e8fa0c7d2
Create Date: 2026-08-27 16:40:00.000000

内容
----
客户列表行内的「今日发送/接收」聚合(customer.py 的 send_today/receive_today)
按 ``channel=? AND owner IN (...) AND timestamp>=今日`` GROUP BY owner/talker。
两个既有索引把 timestamp 排在 talker/room 之后,时间范围无法 seek——字面量
SQL 时优化器还能忍(索引全扫 92 万项 0.23s),但 asyncmy 走**服务端预编译**,
优化器弃索引转全表扫 86 万含大文本的宽行:**7.7s/次**,前端客户列表每次翻页
都撞(2026-08-27 用户报「微信客户列表加载慢」实测 API 7.6s)。

本迁移补 (channel, owner_account_id, timestamp) 三列索引:owner 前缀下按
timestamp 直接落入当天几百行,实测 0.14s → API 全链 0.097s(78 倍)。窄列
BTREE,86 万行在线建索引实测 16s。

幂等:``sa.inspect`` 先查同名索引,存在即跳过。SQLite/MySQL 通用。
"""
from collections.abc import Sequence

import sqlalchemy as sa
from alembic import op


# revision identifiers, used by Alembic.
revision: str = 'c53f90b1e6a4'
down_revision: str | Sequence[str] | None = 'b41e8fa0c7d2'
branch_labels: str | Sequence[str] | None = None
depends_on: str | Sequence[str] | None = None

_INDEX_NAME = 'ix_message_channel_owner_time'


def _has_index(table: str, index: str) -> bool:
    insp = sa.inspect(op.get_bind())
    return index in {i['name'] for i in insp.get_indexes(table)}


def upgrade() -> None:
    """Upgrade schema."""
    if _has_index('message', _INDEX_NAME):
        return  # 已建过(或先手工建过),幂等跳过
    op.create_index(
        _INDEX_NAME,
        'message',
        ['channel', 'owner_account_id', 'timestamp'],
    )


def downgrade() -> None:
    """Downgrade schema."""
    if not _has_index('message', _INDEX_NAME):
        return
    op.drop_index(_INDEX_NAME, table_name='message')