# 数据库设计（SQLite）

数据库文件默认位置：`/data/csp.db`（Docker volume `csp_data` 持久化）。

## 1. 核心表

### `users`
- `id` INTEGER PK AUTOINCREMENT
- `username` TEXT UNIQUE
- `password_salt` TEXT
- `password_hash` TEXT
- `rating` INTEGER DEFAULT 0
- `created_at` INTEGER

### `sessions`
- `token` TEXT PK
- `user_id` INTEGER FK -> users.id
- `expires_at` INTEGER
- `created_at` INTEGER

### `problems`
- `id` INTEGER PK AUTOINCREMENT
- `slug` TEXT UNIQUE
- `title` TEXT
- `statement_md` TEXT
- `difficulty` INTEGER
- `source` TEXT
- `statement_url` TEXT（原始 PDF/题面链接）
- `llm_profile_json` TEXT（固定 JSON：难度、答案、讲解、知识点、标签等）
- `sample_input` TEXT
- `sample_output` TEXT
- `created_at` INTEGER

### `problem_tags`
- `problem_id` INTEGER FK -> problems.id
- `tag` TEXT
- PK(`problem_id`, `tag`)

### `submissions`
- `id` INTEGER PK AUTOINCREMENT
- `user_id` INTEGER FK -> users.id
- `problem_id` INTEGER FK -> problems.id
- `contest_id` INTEGER NULL FK -> contests.id
- `language` TEXT
- `code` TEXT
- `status` TEXT (`Pending/Compiling/Running/AC/WA/TLE/MLE/RE/CE/Unknown`)
- `score` INTEGER
- `time_ms` INTEGER
- `memory_kb` INTEGER
- `compile_log` TEXT
- `runtime_log` TEXT
- `created_at` INTEGER

### `wrong_book`
- `user_id` INTEGER FK -> users.id
- `problem_id` INTEGER FK -> problems.id
- `last_submission_id` INTEGER NULL FK -> submissions.id
- `note` TEXT
- `updated_at` INTEGER
- PK(`user_id`, `problem_id`)

### `contests`
- `id` INTEGER PK AUTOINCREMENT
- `title` TEXT
- `starts_at` INTEGER
- `ends_at` INTEGER
- `rule_json` TEXT

### `contest_problems`
- `contest_id` INTEGER FK -> contests.id
- `problem_id` INTEGER FK -> problems.id
- `idx` INTEGER
- PK(`contest_id`, `problem_id`)

### `contest_registrations`
- `contest_id` INTEGER FK -> contests.id
- `user_id` INTEGER FK -> users.id
- `registered_at` INTEGER
- PK(`contest_id`, `user_id`)

### `kb_articles`
- `id` INTEGER PK AUTOINCREMENT
- `slug` TEXT UNIQUE
- `title` TEXT
- `content_md` TEXT
- `created_at` INTEGER

### `kb_article_links`
- `article_id` INTEGER FK -> kb_articles.id
- `problem_id` INTEGER FK -> problems.id
- PK(`article_id`, `problem_id`)

### `import_jobs`
- `id` INTEGER PK AUTOINCREMENT
- `status` TEXT（`running/success/partial_failed/failed`）
- `trigger` TEXT（`auto/manual`）
- `total_count` / `processed_count` / `success_count` / `failed_count`
- `options_json` TEXT（本次导入参数快照）
- `last_error` TEXT
- `started_at` / `finished_at` / `updated_at` / `created_at`

### `import_job_items`
- `id` INTEGER PK AUTOINCREMENT
- `job_id` INTEGER FK -> import_jobs.id
- `source_path` TEXT
- `status` TEXT（`queued/running/success/failed`）
- `title` TEXT
- `difficulty` INTEGER
- `problem_id` INTEGER NULL FK -> problems.id
- `error_text` TEXT
- `started_at` / `finished_at` / `updated_at` / `created_at`
- UNIQUE(`job_id`, `source_path`)

## 2. 关键索引

- `idx_submissions_user_created_at`
- `idx_submissions_problem_created_at`
- `idx_submissions_contest_user_created_at`
- `idx_problem_tags_tag`
- `idx_kb_article_links_problem_id`
- `idx_import_jobs_created_at`
- `idx_import_jobs_status`
- `idx_import_job_items_job_status`

## 3. 初始化与演示数据

系统启动时会自动：

1. 执行 `ApplyMigrations`
2. 执行 `SeedDemoData`

演示数据包含：

- 基础题目（A+B、Fibonacci、排序）
- 题目标签（math/dp/sort 等）
- 知识库文章（快速 IO、DP 入门）
- 示例模拟赛（含题目关联）