```sql
CREATE TABLE IF NOT EXISTS users (
  username TEXT PRIMARY KEY,
  password TEXT NOT NULL,
  created_at INTEGER NOT NULL DEFAULT (strftime('%s', 'now'))
);

CREATE TABLE IF NOT EXISTS play_records (
  id INTEGER PRIMARY KEY AUTOINCREMENT,
  username TEXT NOT NULL,
  key TEXT NOT NULL,
  title TEXT NOT NULL,
  source_name TEXT NOT NULL,
  cover TEXT NOT NULL,
  year TEXT NOT NULL,
  index_episode INTEGER NOT NULL,
  total_episodes INTEGER NOT NULL,
  play_time INTEGER NOT NULL,
  total_time INTEGER NOT NULL,
  save_time INTEGER NOT NULL,
  search_title TEXT,
  UNIQUE(username, key)
);

CREATE TABLE IF NOT EXISTS favorites (
  id INTEGER PRIMARY KEY AUTOINCREMENT,
  username TEXT NOT NULL,
  key TEXT NOT NULL,
  title TEXT NOT NULL,
  source_name TEXT NOT NULL,
  cover TEXT NOT NULL,
  year TEXT NOT NULL,
  total_episodes INTEGER NOT NULL,
  save_time INTEGER NOT NULL,
  UNIQUE(username, key)
);

CREATE TABLE IF NOT EXISTS search_history (
  id INTEGER PRIMARY KEY AUTOINCREMENT,
  username TEXT NOT NULL,
  keyword TEXT NOT NULL,
  created_at INTEGER NOT NULL DEFAULT (strftime('%s', 'now')),
  UNIQUE(username, keyword)
);

CREATE TABLE IF NOT EXISTS admin_config (
  id INTEGER PRIMARY KEY DEFAULT 1,
  config TEXT NOT NULL,
  updated_at INTEGER NOT NULL DEFAULT (strftime('%s', 'now'))
);

-- 基本索引
CREATE INDEX IF NOT EXISTS idx_play_records_username ON play_records(username);
CREATE INDEX IF NOT EXISTS idx_favorites_username ON favorites(username);
CREATE INDEX IF NOT EXISTS idx_search_history_username ON search_history(username);

-- 复合索引优化查询性能
-- 播放记录：用户名+键值的复合索引，用于快速查找特定记录
CREATE INDEX IF NOT EXISTS idx_play_records_username_key ON play_records(username, key);
-- 播放记录：用户名+保存时间的复合索引，用于按时间排序的查询
CREATE INDEX IF NOT EXISTS idx_play_records_username_save_time ON play_records(username, save_time DESC);

-- 收藏：用户名+键值的复合索引，用于快速查找特定收藏
CREATE INDEX IF NOT EXISTS idx_favorites_username_key ON favorites(username, key);
-- 收藏：用户名+保存时间的复合索引，用于按时间排序的查询
CREATE INDEX IF NOT EXISTS idx_favorites_username_save_time ON favorites(username, save_time DESC);

-- 搜索历史：用户名+关键词的复合索引，用于快速查找/删除特定搜索记录
CREATE INDEX IF NOT EXISTS idx_search_history_username_keyword ON search_history(username, keyword);
-- 搜索历史：用户名+创建时间的复合索引，用于按时间排序的查询
CREATE INDEX IF NOT EXISTS idx_search_history_username_created_at ON search_history(username, created_at DESC);

-- 搜索历史清理查询的优化索引
CREATE INDEX IF NOT EXISTS idx_search_history_username_id_created_at ON search_history(username, id, created_at DESC);
```