"""message 补无渠道前缀索引 (owner_account_id, talker_id, timestamp)

Revision ID: d8e9f0a1b2c3
Revises: c9d0e1f2a3b4
Create Date: 2026-09-10

背景:该回未回决赛圈点查在 channel=None(管理驾驶舱 action_counts)时
无渠道前缀条件,现有索引全部以 channel 打头用不上——服务器 100 万行
实测 dashboard 34~37s 撞前端 15s 超时;索引落地后 1.3~1.8s。
幂等:sa.inspect 先查,存在即跳过(服务器已先行手工建同名索引,本迁移
兜底对齐 schema 版本)。「模型+迁移双声明」防 autogenerate 反 DROP。
"""
from collections.abc import Sequence

import sqlalchemy as sa
from alembic import op

revision: str = "d8e9f0a1b2c3"
down_revision: str | Sequence[str] | None = "c9d0e1f2a3b4"
branch_labels: str | Sequence[str] | None = None
depends_on: str | Sequence[str] | None = None

_IDX = "ix_message_owner_talker_time"


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


def upgrade() -> None:
    if not _has_index(op.get_bind()):
        op.create_index(_IDX, "message",
                         ["owner_account_id", "talker_id", "timestamp"])


def downgrade() -> None:
    if _has_index(op.get_bind()):
        op.drop_index(_IDX, table_name="message")