"""adj_factor 覆盖索引：因子查询免堆访问（碎片免疫）

Revision ID: 20260902_01
Revises: 20260815_04
Create Date: 2026-09-02
"""
from typing import Sequence, Union

from alembic import op

revision: str = "20260902_01"
down_revision: Union[str, Sequence[str], None] = "20260815_04"
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    # CONCURRENTLY / VACUUM 不能在事务内执行；autocommit_block 内每条语句独立提交
    with op.get_context().autocommit_block():
        op.create_index(
            "ix_adj_code_date_cover",
            "adj_factor",
            ["ts_code", "trade_date"],
            postgresql_concurrently=True,
            postgresql_include=["adj_factor"],
        )
        # ts_code 单列索引被覆盖索引取代（同前缀），删掉省写放大
        op.drop_index(
            "ix_adj_factor_ts_code",
            table_name="adj_factor",
            postgresql_concurrently=True,
        )
        # 刷可见性映射（Index Only Scan 的前提）+ 更新统计信息；低峰执行（3.2GB 表数十秒）
        op.execute("VACUUM (ANALYZE) adj_factor")


def downgrade() -> None:
    with op.get_context().autocommit_block():
        op.create_index(
            "ix_adj_factor_ts_code",
            "adj_factor",
            ["ts_code"],
            postgresql_concurrently=True,
        )
        op.drop_index(
            "ix_adj_code_date_cover",
            table_name="adj_factor",
            postgresql_concurrently=True,
        )