"""5 表 updated_at 窄索引——/api/analytics/health MAX 消除全表扫

Revision ID: c3d4e5f6a7b8
Revises: f0a1b2c3d4e5
Create Date: 2026-09-04

health 端点每页面加载对 6 表各 MAX 一次;5 表 updated_at 无索引时
MySQL 全表扫(media 5万宽行在 128MB buffer pool 下最伤)。单列窄索引
各几 MB,MAX 变 O(1) 索引定位。幂等:_has_index 先查。SQLite/MySQL 通用。
模型侧 models.py 同步双声明,防 alembic autogenerate 反 DROP。
"""
from collections.abc import Sequence

import sqlalchemy as sa
from alembic import op

revision: str = "c3d4e5f6a7b8"
down_revision: str | Sequence[str] | None = "f0a1b2c3d4e5"
branch_labels: str | Sequence[str] | None = None
depends_on: str | Sequence[str] | None = None

# (表名, 索引名) —— 与 models.py 各模型 __table_args__ 一字对应
_INDEXES: tuple[tuple[str, str], ...] = (
    ("customer", "ix_customer_updated_at"),
    ("chat_group", "ix_chat_group_updated_at"),
    ("phone_call", "ix_phone_call_updated_at"),
    ("media", "ix_media_updated_at"),
    ("moments_post", "ix_moments_post_updated_at"),
)


def _has_index(bind, table: str, index: str) -> bool:
    insp = sa.inspect(bind)
    if not insp.has_table(table):
        return False
    return index in {ix["name"] for ix in insp.get_indexes(table)}


def upgrade() -> None:
    bind = op.get_bind()
    for table, index in _INDEXES:
        if not _has_index(bind, table, index):
            op.create_index(index, table, ["updated_at"])


def downgrade() -> None:
    bind = op.get_bind()
    for table, index in _INDEXES:
        if _has_index(bind, table, index):
            op.drop_index(index, table_name=table)