"""清理废案 search_title_suggestions 相关对象。

设计:产品迭代决定只展示 keyword 续接词,titles 段(真实文章 id 提示)被砍。
但 0009 迁移里建的相关对象还在:
- search_title_suggestions 表 + 3 个 GIN/B-tree 索引
- articles trigger trg_articles_rebuild_title_suggestions
- rebuild_title_suggestions() PL/pgSQL 函数

每篇文章 INSERT/UPDATE 都要跑 trigger(性能损耗),删干净。

也清理:
- app/models/search_title_suggestion.py 文件(本次 commit 不删文件,只删 __init__ 引用)
- app/scripts/backfill_search_suggestions.py 现在回灌的也是 search_title_suggestions
  → 整体替换成"无 op 脚本"(或者改名为只跑一次 refresh_search_keywords)

Revision ID: 0011
Revises: 0010
Create Date: 2026-06-15
"""
from __future__ import annotations

from typing import Sequence, Union

import sqlalchemy as sa
from alembic import op


revision: str = "0011"
down_revision: Union[str, None] = "0010"
branch_labels = None
depends_on = None


def upgrade() -> None:
    # 1) 删 trigger(挂 articles 上)
    op.execute("DROP TRIGGER IF EXISTS trg_articles_rebuild_title_suggestions ON articles")

    # 2) 删 trigger 函数
    op.execute("DROP FUNCTION IF EXISTS rebuild_title_suggestions()")

    # 3) 删表 + 索引(ON DELETE CASCADE 让 articles delete 一起清)
    op.drop_index("ix_search_title_suggestions_published", table_name="search_title_suggestions")
    op.drop_index("ix_search_title_suggestions_article", table_name="search_title_suggestions")
    op.drop_index("ix_search_title_suggestions_prefix", table_name="search_title_suggestions")
    op.drop_table("search_title_suggestions")


def downgrade() -> None:
    # 重新建表(产品迭代回滚时用 — schema 跟 0009 一致)
    op.create_table(
        "search_title_suggestions",
        sa.Column("id", sa.BigInteger, primary_key=True),
        sa.Column(
            "article_id",
            sa.BigInteger,
            sa.ForeignKey("articles.id", ondelete="CASCADE"),
            nullable=False,
        ),
        sa.Column("title_lang", sa.String(8), nullable=False, server_default="zh"),
        sa.Column("prefix_keys", sa.ARRAY(sa.Text), nullable=False),
        sa.Column("published_at", sa.DateTime(timezone=True), nullable=True),
        sa.Column(
            "created_at",
            sa.DateTime(timezone=True),
            nullable=False,
            server_default=sa.text("now()"),
        ),
    )
    op.create_index(
        "ix_search_title_suggestions_prefix",
        "search_title_suggestions",
        ["prefix_keys"],
        postgresql_using="gin",
    )
    op.create_index(
        "ix_search_title_suggestions_article",
        "search_title_suggestions",
        ["article_id"],
    )
    op.create_index(
        "ix_search_title_suggestions_published",
        "search_title_suggestions",
        ["published_at"],
    )
    op.execute(
        """
        CREATE OR REPLACE FUNCTION rebuild_title_suggestions() RETURNS TRIGGER AS $$
        DECLARE
            src_text text;
            src_lang text;
            max_len int := 50;
        BEGIN
            DELETE FROM search_title_suggestions WHERE article_id = NEW.id;
            IF NEW.title_zh IS NOT NULL AND length(NEW.title_zh) > 0 THEN
                src_text := NEW.title_zh;
                src_lang := 'zh';
            ELSIF NEW.title IS NOT NULL AND length(NEW.title) > 0 THEN
                src_text := NEW.title;
                src_lang := 'src';
            ELSE
                RETURN NEW;
            END IF;
            src_text := substring(src_text, 1, max_len);
            INSERT INTO search_title_suggestions
                (article_id, title_lang, prefix_keys, published_at)
            SELECT NEW.id, src_lang,
                   ARRAY(SELECT substring(src_text, 1, n)
                         FROM generate_series(1, length(src_text)) AS n),
                   NEW.published_at;
            RETURN NEW;
        END;
        $$ LANGUAGE plpgsql;
        """
    )
    op.execute(
        """
        CREATE TRIGGER trg_articles_rebuild_title_suggestions
        AFTER INSERT OR UPDATE OF title_zh, title, published_at ON articles
        FOR EACH ROW EXECUTE FUNCTION rebuild_title_suggestions();
        """
    )