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Date: Fri, 25 Sep 2026 14:21:55 +0800
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---
 README.md                                    | 198 ++++++++-
 benchmark/README.md                          |  93 ----
 benchmark/chusql-storage/Cargo.lock          | 334 ++++++++++++++
 benchmark/chusql-storage/Cargo.toml          |  16 +
 benchmark/chusql-storage/README.md           |  36 --
 benchmark/chusql-storage/benches/storage.rs  | 353 +++++++++++++++
 benchmark/fullchain/chusql-fullchain.cabal   |  17 +
 benchmark/fullchain/src/Main.hs              | 435 +++++++++++++++++++
 benchmark/fullchain/stack.yaml               |   5 +
 benchmark/fullchain/stack.yaml.lock          |  12 +
 chusql-engine/chusql-engine.cabal            |   2 +
 chusql-engine/src/ChuSQL/Algebra/Eval.hs     |  94 +++-
 chusql-engine/src/ChuSQL/Algebra/Op.hs       |   8 +-
 chusql-engine/src/ChuSQL/Algebra/Optimize.hs |  12 +-
 chusql-engine/src/ChuSQL/Engine.hs           |  78 ++--
 chusql-engine/src/ChuSQL/Model.hs            |  22 +-
 chusql-engine/src/ChuSQL/Semantic.hs         |  19 +-
 chusql-engine/src/ChuSQL/Storage.hs          |  75 +++-
 chusql-engine/src/ChuSQL/Storage/IPC.hs      | 260 +++++++----
 chusql-engine/src/ChuSQL/Storage/Memory.hs   |  19 +-
 chusql-engine/src/ChuSQL/Syntax/AST.hs       |   8 +-
 chusql-engine/src/ChuSQL/Syntax/Parser.hs    |  45 +-
 chusql-engine/test/Spec.hs                   | 203 +++++++--
 chusql-storage/src/bin/server.rs             | 399 +++++++++++++----
 chusql-storage/src/btree.rs                  |  35 ++
 chusql-storage/src/catalog.rs                | 208 +++++++--
 chusql-storage/src/heap.rs                   | 354 ++++++++++++---
 chusql-storage/src/protocol.rs               |  84 +++-
 chusql-storage/src/wal.rs                    | 102 ++++-
 chusql-storage/tests/btree_test.rs           |  60 +++
 chusql-storage/tests/heap_test.rs            | 167 ++++++-
 chusql-storage/tests/pipe_test.rs            | 172 +++++++-
 chusql-storage/tests/wal_test.rs             |   5 +-
 33 files changed, 3332 insertions(+), 598 deletions(-)
 delete mode 100644 benchmark/README.md
 create mode 100644 benchmark/chusql-storage/Cargo.lock
 create mode 100644 benchmark/chusql-storage/Cargo.toml
 delete mode 100644 benchmark/chusql-storage/README.md
 create mode 100644 benchmark/chusql-storage/benches/storage.rs
 create mode 100644 benchmark/fullchain/chusql-fullchain.cabal
 create mode 100644 benchmark/fullchain/src/Main.hs
 create mode 100644 benchmark/fullchain/stack.yaml
 create mode 100644 benchmark/fullchain/stack.yaml.lock

diff --git a/README.md b/README.md
index 342d116..5f46f83 100644
--- a/README.md
+++ b/README.md
@@ -43,16 +43,192 @@
 > 如果找到了较好的Rust+Haskell集成方法也会及时替换
 
 # 性能基准
-**测试环境**：Windows / GHC 9.10.3 / `-O2`
-**数据规模**：`users`、`orders` 各 500 行，两表配对共 25 万对
-**计时方式**：CPU 时间；每批至少 8 次迭代、累计超过 0.3 秒后固定批次，取 3 批中位数（避开时钟量化误差）
 
-| 查询                                       | 结果行数 |   未优化 |      优化后 |      加速 |
-| ------------------------------------------ | -------: | -------: | ----------: | --------: |
-| `JOIN` + `WHERE u.age > 90`                |       45 | 156.3 ms | **12.2 ms** | **12.8x** |
-| `JOIN`（无 WHERE，只有投影）               |      500 | 169.9 ms |    146.5 ms |      1.2x |
-| `JOIN` + `WHERE` + `ORDER BY` + `LIMIT 10` |       10 | 175.8 ms | **13.7 ms** | **12.9x** |
-| 单表 `WHERE age > 90`（对照组）            |       45 | 0.183 ms |    0.275 ms |      0.7x |
+三个基准，各管一件事，**主基准是全链路**（Haskell 引擎和 Rust 存储进程一起启动，跑真实情景）：
 
-> 跑法：`cd benchmark/chusql-engine && stack run`（可选参数：`用户行数 订单数 单批目标秒数`，默认 `500 500 0.3`）
-> 最近更新：2026-09-24
+| 基准 | 位置 | 测什么 |
+| ---- | ---- | ------ |
+| **全链路** | `benchmark/fullchain/` | SQL 文本 → 引擎 → 命名管道 → Rust → WAL/堆表/索引 → 落盘，整条路 |
+| 查询层 | `benchmark/chusql-engine/` | 只用内存数据，隔离出优化器与连接算法的效果 |
+| 存储层 | `benchmark/chusql-storage/` | Rust 侧页 IO / B+ 树 / 堆表 / WAL 的微基准 |
+
+## 全链路：Haskell + Rust 一起跑
+
+```bash
+cd chusql-storage && cargo build --release     # 先编译存储进程（找不到 release 会用 debug 并提醒你）
+cd benchmark/fullchain
+stack run chusql-fullchain                     # 默认 users = orders = 200
+stack run chusql-fullchain -- 1000 1000        # 换规模
+# 改过 chusql-engine 源码之后，先 stack build --force-dirty 再跑（原因见"计时怎么做"的坑四）
+```
+
+它做的事：造一个临时数据目录和独立管道名 → 起 Rust 存储进程 → 用引擎的 IPC 存储连上去 →
+按真实情景跑一遍（建表、逐条 INSERT、全表 SELECT、过滤、JOIN、按主键点查）→ 校验行数 → 收摊。
+
+**每条语句都是整条链路**：SQL 文本真的要过词法/语法分析、语义检查、关系代数，再走管道到 Rust，
+经 WAL（fsync）、堆表、B+ 树、页缓冲池落到磁盘，结果再原路返回。
+计时用**墙上时钟（单调时钟）**，不是 CPU 时间——这条链路大部分工夫花在等 IO 和跨进程往返上。
+
+### 实测（每条语句平均耗时）
+
+| 指标 | 200 × 200 | 500 × 500 | 1000 × 1000 |
+| ---- | --------: | --------: | ----------: |
+| 单条 `INSERT`（整条语句） | 2.66 ms | 2.86 ms | 2.88 ms |
+| 同一条 `INSERT`（原始 IPC，不经引擎） | 2.50 ms | 2.85 ms | 2.77 ms |
+| **多行 `INSERT`（100 行/条）** | — | — | **0.059 ms/行** |
+| `SELECT * FROM users` | 0.4 ms | 1.0 ms | 1.9 ms |
+| `SELECT name FROM users WHERE age > 90` | 0.3 ms | 0.8 ms | 2.7 ms |
+| `SELECT ... JOIN ... WHERE` | 0.9 ms | 2.4 ms | 5.3 ms |
+| `SELECT name FROM users WHERE id = k` | 0.2 ms | 0.2 ms | 0.2 ms |
+| `DELETE FROM users WHERE id = k`（删 1 行） | — | — | 4.8 ms |
+| `DELETE FROM users`（删全部 1000 行） | — | — | 20.2 ms |
+| `SELECT ... WHERE code = k`（无索引 → 建索引后） | — | — | 1.8 ms → **0.2 ms** |
+
+四条结论：
+
+1. **写入是 fsync 说了算，和数据量无关。** 单条 INSERT 约 2.7 ms。能单独量出来的落盘成本约 1.0 ms
+   （写日志 0.43 + 清日志 0.42 + 表数据 flush 0.15），其余是这几次同步落盘之间的等待和跨进程往返。
+   表从 200 行长到 1000 行，单条耗时基本不动——**插一行和插一千行的落盘代价几乎一样**。
+   所以想快就得多行一起提交：`VALUES (...), (...), ...` 一条语句 100 行，
+   每行 2.88 ms → **0.059 ms（约 49 倍）**。
+2. **点查是 O(1)。** 按主键查一行 0.2 ms（其中原始 IPC 索引查找 0.07 ms），1000 行时仍是 0.2 ms。
+   建在别的列上的索引也一样：`WHERE code = k` 从 1.8 ms（没有索引，退回扫描）降到 0.2 ms。
+3. **删除的代价和"删几行"无关了。** 删 1 行 4.8 ms、删全部 1000 行 20.2 ms：
+   前者就贵在一次全表扫描 + 一次落盘，后者是同一笔扫描加上 1000 次 O(1) 的行级删除。
+   改之前，删 1 行也要把整张表重写一遍并重建整棵索引。
+4. **单表查询与那张表的行数成正比**（1000 行 1.9 ms，约 2 µs/行）。查询层现在的设计是把表拉进内存算，
+   这个数字就是"拉 1000 行过管道 + 在内存里过一遍"的价钱。
+
+## P2 这一版改了什么
+
+四件事，都对应"把整表操作换成行级/批量操作"：
+
+- **① 行级 DELETE。** B+ 树加 `delete`（惰性删除：只摘叶子里的键，不合并节点）；
+  堆表把槽位长度置 0（读侧本来就把"长度 0"当作没有这一行）；查询层的 `DELETE` 改成
+  "扫一遍算出要删哪些 id → `delete_keys` 一次删掉"，不再 `replaceAll` 重写整表。
+- **② 多索引 + `CREATE INDEX` + 规划器选路。** 优化器把"单列等值条件"标成点查节点
+  `Lookup 别名 表 列 值`；**到底有没有索引由存储层回答**——没有就回 `no_index`，查询层退回全表扫描。
+  这样索引元数据只存在数据字典一处，加索引不用改优化器。
+  边界写在下面：**只支持单列整数索引，而且索引列必须唯一**。
+- **③ 批量插入。** 语法支持 `INSERT INTO t (...) VALUES (...), (...), ...`：一条语句走一次 WAL、一次 fsync。
+- **④ 列统计。** 数据字典里每列记"不同值个数"（内存里按值哈希精确维护，上限 4096 之后转下界），
+  随 `catalog.json` 落盘，**启动时扫一遍表重建**，所以重启后数字仍然准；插入/删除实时更新。
+
+### 一个必须讲清楚的取舍：索引列必须唯一
+
+原来的索引只服务 `id`，"唯一"是默认成立的前提。要做通用索引就必须回答一个问题：
+**一个列上有重复值时，"走索引取一行"和"全表扫一遍再筛"还能得到同一个答案吗？**
+现在不能——索引的每个键只放得下一个行位置。所以这一版的规则是：
+
+- 建索引时查重，有重复值就**报错、不建**（不留半成品）；
+- 索引列上插入重复值会被**拒绝**（老代码是"覆盖索引条目"，那会让老行再也查不到）。
+
+真正的解法是让 B+ 树支持重复键（键后面带上行号，再做叶子链上的范围扫描），
+那要把 B+ 树的 `i64` 定长键换成内存可比较的变长字节键——和"复合键"是同一块地基，
+留到单独一轮做。这条限制记在根 README 和 `projectplan.txt` 里，不是忘了。
+
+> 顺带修掉一个旧 bug：点查节点原来会把**别名前缀丢掉**，
+> 于是 `SELECT u.name FROM users u WHERE u.id = 1` 取不到列（投影按 `u.name` 找，
+> 回来的行却是 `name`）。现在 `Lookup` 也带着别名，回来的一行和 `Scan 别名 表` 长得一样，
+> 并且补了对照测试。
+
+## 全链路这一版改了什么：别再为语义检查搬整个库
+
+原来的 `runStatementM` 每条语句都先取一次**整库快照**（把所有表的所有行都拉过管道），
+只为了给语义检查看列名。可是语义检查（`Semantic.check`）和查询优化（`relOpCols`）**只看列，一行数据都不碰**，
+行数据是白搬的——而且每条语句都搬一次，于是单条语句的开销随库变大而线性增长。
+
+改法：给 `MonadStorage` 加一个 `schema`（只要表结构，不要行），默认实现退化成"快照 + 抹掉行",
+`IPCStorage` 覆盖成"只问数据字典要结构"（一次 `list_catalog` 往返，约 0.07 ms），`Engine.runStatementM` 改用它。
+
+1000 × 1000 下的效果：
+
+| 指标 | 改前 | 改后 | 倍率 |
+| ---- | ---: | ---: | ---: |
+| `INSERT INTO users` | 3.65 ms | **2.67 ms** | 1.4x |
+| `INSERT INTO orders` | 5.61 ms | **2.91 ms** | 1.9x |
+| `SELECT * FROM users` | 6.7 ms | **2.0 ms** | 3.4x |
+| `SELECT ... WHERE age > 90` | 6.6 ms | **1.7 ms** | 3.9x |
+| `SELECT ... JOIN ... WHERE` | 11.2 ms | **4.0 ms** | 2.8x |
+| `SELECT ... WHERE id = k` | 3.3 ms | **0.2 ms** | 16x |
+
+改完之后单条 INSERT 的耗时和"原始 IPC 插入"持平（2.67 vs 2.68 ms）——
+**引擎侧的每条语句开销已经小到量不出来**，剩下全是存储层的落盘成本。
+
+## 查询层：等值连接改成哈希表
+
+`Join` 原来是"两边两两配对再筛"：25 万对，每对拼一次行、按列名查两次值，单对约 0.66 µs，
+乘起来就是 165 ms 上下——这正是下表"未优化"那一列的全部耗时。
+现在条件是 `a = b` 这种两列等值时，先拿右表建哈希表、再拿左表逐行探测，配对次数降到 1000 次哈希查找；
+认不出等值键时自动退回嵌套循环，输出顺序与原来完全一致。
+
+数据规模 users / orders 各 500 行（配对 25 万对），中位数，单位 ms：
+
+| 查询                                       | 结果行数 | 改前 未优化 | 改后 未优化 | 改前 优化后 | 改后 优化后 |
+| ------------------------------------------ | -------: | ----------: | ----------: | ----------: | ----------: |
+| `JOIN` + `WHERE u.age > 90`                |       45 |   110.4 ms | **0.267 ms** | 8.9 ms | **0.30 ms** |
+| `JOIN`（无 WHERE，只有投影）               |      500 |   135.7 ms | **0.397 ms** | 111.3 ms | **0.549 ms** |
+| `JOIN` + `WHERE` + `ORDER BY` + `LIMIT 10` |       10 |   130.9 ms | **0.336 ms** | 9.2 ms | **0.320 ms** |
+| 单表 `WHERE age > 90`（对照组）            |       45 |   0.095 ms |    0.084 ms | 0.149 ms | 0.13 ms |
+
+**连接类查询约 300 倍；换成 2000 行 / 400 万对时是 500~900 倍**（嵌套循环是 O(左 × 右)，哈希连接是线性，规模越大省得越多）。
+
+需要注意：表里"优化器开/关"的比值从原来的 12~17 倍降到了 1.0 倍左右——
+**不是优化器变差了，是分母变了**：原来那十几倍几乎全来自"条件把配对次数从 25 万筛到 2.25 万"，
+而连接本身只要 0.4 ms 之后，下推省下的时间已不占主导。**看性能要看绝对耗时，不是比值。**
+
+## 存储层：写入路径
+
+单条 `INSERT` 的完整流程（清 WAL → 写 WAL → 改数据 → 落盘 → 清 WAL）原来约 **3.8 ms**，现在约 **2.5 ms**：
+
+- **WAL 文件句柄常驻**：原来每条操作要 open/close 三次，而 append 模式下开完再 fsync 比看起来的 open 更贵；
+  实测单次追加 990 µs → 507 µs。
+- **写前那次清空只截断、不单独 fsync**：紧跟其后的 `append` 会 fsync，那一次会把截断一起落下去。
+  这一项从 522~600 µs 降到 11.6 µs。
+
+写入路径的瓶颈**是 fsync 次数，不是数据量**。剩下的时间基本都是"真落盘"，而这是 WAL 语义要求的：
+再往下压就要动"每条操作都截断 WAL"这个设计本身（真正的数据库是顺序追加 + 检查点，而不是写一条清一次）。
+
+其余微基准（n = 2000）：页顺序写 15~17 µs/页（含 flush）、页顺序读 4.1~4.5 µs/页、
+B+ 树插入 17.9 µs/次、点查 14.8~16.1 µs/次、堆表扫描 0.5 µs/行。
+
+## 计时怎么做（四个坑都踩过了）
+
+**坑一：Haskell 是惰性的，不强制求值就等于没测。**
+只写 `let r = evalRelOp db plan`，`r` 根本没被算出来，测到的是"定义一个变量"的时间。
+所以每次必须把结果算到底（项目里是逐行把列数累加起来当校验和，或者把行数 `evaluate` 出来）。
+
+**坑二：Windows 上 CPU 时钟的精度只有约 15.6 毫秒。**
+毫秒级的用例直接测会得到 `0.0 ms` 这种没意义的数字。
+查询层基准用**自适应批量**（同一用例连跑 `k` 次，`k` 翻倍到一批超过 0.3 秒再折算成单次），
+把时钟误差摊薄；全链路基准因为是 IO 密集、单次就有毫秒级，直接用墙上单调时钟。
+
+**坑三：机器会漂移。** 同一份代码、同一天、前后隔半小时，指标能整体差 15~25%（温度、后台进程都算）。
+所以：改前改后必须**同一时段交叉测**；小于 2 倍的差异，没交叉验证之前不要当结论。
+
+**坑四（本项目的专属坑）：小心链到旧引擎。** `benchmark/fullchain` 和 `chusql-engine` 在同一个 stack 项目里，
+改完引擎源码后 stack 有时不会把依赖库重新拷进基准项目的安装目录——于是你测的是旧引擎，
+而且数字看起来"合理"。**改过引擎就先 `stack build --force-dirty`。**
+（这一条是实测踩出来的：一次"改动没效果"的排查，最后发现是引擎库的时间戳比源码还旧。）
+
+## 试过但没留下的（别重复踩）
+
+| 想法 | 结果 | 结论 | 为什么 |
+| ---- | ---- | ---- | ------ |
+| 给 Haskell 库加 `-O2` | 加完 8 项全部慢 15~25%；**去掉后重建再测，一样慢** | **已回退** | 这次"变慢"是机器漂移，不是 `-O2` 造成的——但回退后也没测出 `-O2` 的好处。**结论：没有证据**，要么同轮交叉测再下判断，要么别加 |
+| 换掉缓冲池的 `min_by_key` 淘汰 | 池 1024 / 工作集超池：随机读 7.9 µs vs 池 16：5.1 µs | 未做 | 差距是真的（缺页时多扫 1024 个候选页），但只影响"工作集大于池"的随机读，绝对量 ~2.8 µs/次；而写入路径是 2500 µs/次，不在一个量级 |
+| 把投影下推进 `Scan`（Scan 自带列清单） | 未做 | 待定 | 能消掉"无 WHERE 的 JOIN"多出来的那趟投影（约 25%，0.1 ms 级），但要改 `RelOp` 类型、`relOpCols`、Eval 和一堆测试 |
+| 非唯一索引（一个键多条记录） | 未做 | 待定 | 要 B+ 树允许重复键（键后面带行号）+ 叶子链上的范围扫描；和"复合键"共用同一块地基：**键从 `i64` 定长槽位改成内存可比较的变长字节键** |
+| 只给索引加"唯一"检查、不改插入语义 | 未做 | 已否 | 那样建索引时唯一、之后插重复值仍会把老行"挤"出索引，查询结果就和全表扫不一致了——宁可插入时报错 |
+
+## 怎么加用例
+
+- **全链路**：在 `benchmark/fullchain/src/Main.hs` 的 `runScenarios` 里加 `benchSql label sql` 就行；
+  要验证结果就照着 `[校验]` 那一段写断言（现在的两个校验是 `age > 90` 的行数和 JOIN 的行数）。
+- **查询层**：在 `benchmark/chusql-engine/src/Main.hs` 的 `queries` 列表里加一条 SQL 字符串，其余全自动
+  （自动翻译、优化、跑两遍、比结果、算加速比）。
+- **存储层**：在 `benchmark/chusql-storage/benches/storage.rs` 里加一段 `bench(...)` / `bench_once(...)`。
+
+想在文档里引用数字，记得把**数据规模、机器、时间**一起写上——脱离这些谈"快了几倍"没有意义。
+
+> 最近更新：2026-09-25
diff --git a/benchmark/README.md b/benchmark/README.md
deleted file mode 100644
index c8fd04e..0000000
--- a/benchmark/README.md
+++ /dev/null
@@ -1,93 +0,0 @@
-# ChuSQL 基准测试
-
-这个目录放**性能基准测试**，和 `chusql-engine`、`chusql-storage` 的功能代码分开，
-因为它回答的问题不一样：功能代码回答"对不对"，基准测试回答"快不快、快多少"。
-
-```
-benchmark/
-├── README.md                  本文件：怎么跑、测什么、结果怎么解读
-├── chusql-engine/             Haskell 查询层：优化器开/关的对比
-│   ├── stack.yaml             把 chusql-engine 作为本地包引入
-│   ├── chusql-bench.cabal
-│   └── src/Main.hs
-└── chusql-storage/            Rust 存储层：预留（见该目录下的 README）
-```
-
----
-
-## 怎么跑
-
-```bash
-cd benchmark/chusql-engine
-stack run                      # 默认 users=500 行、orders=500 行
-stack run -- 1000 1000 0.5     # 也可以自己指定：users 行数、orders 行数、每批目标秒数
-```
-
-第一次跑要编译，之后很快。整个默认跑完约 5 秒。
-
----
-
-## 测什么
-
-四个用例，**每个都跑两遍**：一遍走"翻译出来的原始工序单"，一遍走"优化后的工序单"。
-两次的结果行数会被打印出来互相对照，**不一致会当场标出来**。
-
-| 用例 | 想看什么 |
-| ---- | -------- |
-| `JOIN` + `WHERE u.age > 90` | 谓词下推的主场：条件能筛掉约 90% 的行 |
-| `JOIN`（无 WHERE） | 只剩投影下推在起作用，收益应该温和 |
-| `JOIN` + `WHERE` + `ORDER BY` + `LIMIT` | 规则叠加时的综合效果 |
-| 单表 `WHERE age > 90` | 对照组：没有下推空间，优化器只剩固定开销 |
-
----
-
-## 计时怎么做（两个坑都踩过了）
-
-**坑一：Haskell 是惰性的，不强制求值就等于没测。**
-如果只写 `let r = evalRelOp db plan`，`r` 根本没被算出来，测到的是"定义一个变量"的时间。
-所以每次必须把结果**算到底**（本项目里是逐行把列数累加起来当校验和）。
-
-**坑二：Windows 上 CPU 时钟的精度只有约 15.6 毫秒。**
-优化后的查询只要几毫秒，直接测会得到 `0.0 ms` 这种没意义的数字。
-
-所以计时用的是**自适应批量**：把同一个用例连续跑 `k` 次测一整批，`k` 不断翻倍，
-直到一批累计耗时超过目标值（默认 0.3 秒），再折算成单次耗时。
-这样时钟精度的误差会被 `k` 摊薄，几毫秒的用例也能测准。
-程序会打印实际用了多大的批次（例如"优化后 64 次/批"）。
-
-跑正式计时之前还会**预热两遍**，避免把首次构造表数据的开销算进去。
-
----
-
-## 实测结果
-
-**环境**：Windows，GHC 9.10.3，`-O2`
-**数据**：`users` 500 行（`id / name / age`，`age` 只有 0-99 共 100 种取值），
-`orders` 500 行（`id / user_id / product`），两表配对共 25 万对。
-
-| 查询 | 结果行数 | 未优化 | 优化后 | 加速 |
-| ---- | -------- | ------ | ------ | ---- |
-| `JOIN` + `WHERE u.age > 90` | 45 | 125.0 ms | **7.1 ms** | **17.7x** |
-| `JOIN`（无 WHERE） | 500 | 132.8 ms | 105.5 ms | 1.3x |
-| `JOIN` + `WHERE` + `ORDER BY` + `LIMIT 10` | 10 | 171.9 ms | **10.3 ms** | **16.8x** |
-| 单表 `WHERE age > 90` | 45 | 0.111 ms | 0.153 ms | 0.7x |
-
-### 怎么解读
-
-- **前两行的差距来自谓词下推。** 条件筛掉了约 90% 的用户，配对次数从 25 万降到约 2.25 万，
-  时间直接掉一个数量级。筛得越狠，省得越多。
-- **第二行只有投影下推。** 配对次数一点没变（没有条件可下推），只是每一行变窄了，
-  所以只有 1.3 倍 —— 收益温和但确实是正的。
-- **第四行反而略慢。** 单表查询本来就没有下推空间（条件早已贴着扫描），
-  而优化器自己要走一遍规则，有几十微秒的固定开销（0.153 − 0.111 ≈ 0.04 ms）。
-  **优化不是零成本的**：查询越大、配对越多，这笔账才越划算。
-
----
-
-## 加新用例
-
-在 `src/Main.hs` 的 `queries` 列表里加一条 SQL 字符串就行，其余全自动
-（会自动翻译、优化、跑两遍、比结果、算加速比）。
-
-想测别的规模，直接命令行传参；想在文档里引用数字，记得把**数据规模一起写上** ——
-脱离规模谈"快了几倍"是没有意义的。
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diff --git a/benchmark/chusql-storage/Cargo.toml b/benchmark/chusql-storage/Cargo.toml
new file mode 100644
index 0000000..51fef18
--- /dev/null
+++ b/benchmark/chusql-storage/Cargo.toml
@@ -0,0 +1,16 @@
+[package]
+name = "chusql-storage-bench"
+version = "0.1.0"
+edition = "2024"
+
+# 存储层基准单独成包，不混进功能代码（见同目录 README）。
+[dependencies]
+chusql-storage = { path = "../../chusql-storage" }
+serde_json = "1"
+
+[dev-dependencies]
+tempfile = "3"
+
+[[bench]]
+name = "storage"
+harness = false
diff --git a/benchmark/chusql-storage/README.md b/benchmark/chusql-storage/README.md
deleted file mode 100644
index 9e539cd..0000000
--- a/benchmark/chusql-storage/README.md
+++ /dev/null
@@ -1,36 +0,0 @@
-# chusql-storage 基准测试（预留）
-
-这个目录预留给 **Rust 存储层** 的基准测试代码，目前 `chusql-storage/` 还没有开工，
-所以这里先占位。
-
-## 计划放什么
-
-`chusql-storage` 做的是磁盘那一层的事情，性能指标和查询层完全不同 ——
-查询层关心"少算几行"，存储层关心"少读几次盘"。所以基准要分开测：
-
-| 待测模块 | 关心的指标 |
-| -------- | ---------- |
-| 页管理 | 单页读写延迟、顺序读 vs 随机读吞吐 |
-| B+ 树 | 插入/查找/范围扫描的耗时随数据量增长的趋势 |
-| 缓冲池 | 命中率、缺页次数、替换策略（LRU 等）的对比 |
-| WAL | 追加写吞吐、日志落盘延迟、恢复耗时 |
-| 崩溃恢复 | 从日志重放的时间、恢复后数据一致性 |
-
-## 用什么
-
-Rust 侧的基准测试一般用 [criterion](https://github.com/bheisler/criterion.rs)：
-
-```
-benchmark/chusql-storage/
-├── Cargo.toml
-└── benches/
-    ├── page.rs
-    ├── btree.rs
-    ├── buffer_pool.rs
-    └── wal.rs
-```
-
-跑法：`cargo bench`
-
-另外还要和 Haskell 层对齐口径：查询层的基准是"整条查询的耗时"，
-存储层的基准是"单次 IO / 单次查找的耗时"，两边不要混在一起比。
diff --git a/benchmark/chusql-storage/benches/storage.rs b/benchmark/chusql-storage/benches/storage.rs
new file mode 100644
index 0000000..1aaf8d0
--- /dev/null
+++ b/benchmark/chusql-storage/benches/storage.rs
@@ -0,0 +1,353 @@
+//! 存储层基准：页 IO、B+ 树、堆表、WAL 与服务端写入路径。
+//!
+//! 用 `std::time::Instant` 计时，不引第三方基准框架，离线也能跑。
+//! 每项跑 `rounds` 轮取最快一轮：存储层的抖动主要来自 fsync 与调度，
+//! 取最快一轮最接近"这套代码本身要花多久"。
+//!
+//! 跑法：`cargo bench`（可选环境变量 `CHUSQL_BENCH_N` 改规模，默认 2000）
+
+use std::time::{Duration, Instant};
+
+use chusql_storage::btree::DiskBTree;
+use chusql_storage::config::{DEFAULT_BTREE_ORDER, DEFAULT_PAGE_SIZE};
+use chusql_storage::heap::HeapTable;
+use chusql_storage::page::{Page, PageFile};
+use chusql_storage::protocol::Row;
+use chusql_storage::wal::{Wal, WalOp};
+use serde_json::json;
+
+// 工具
+/// 跑一个操作 `ops` 次，量总耗时并折算每次耗时
+fn bench<F: FnMut()>(label: &str, ops: usize, rounds: usize, mut f: F) {
+    let mut best = Duration::MAX;
+    for _ in 0..rounds {
+        let t0 = Instant::now();
+        f();
+        let d = t0.elapsed();
+        if d < best {
+            best = d;
+        }
+    }
+    let per = best.as_secs_f64() * 1e6 / ops as f64;
+    println!(
+        "{:<38} {:>9.2} ms {:>10.3} us/次",
+        label,
+        best.as_secs_f64() * 1e3,
+        per
+    );
+}
+
+/// 只量一次（fsync 类操作太慢，不适合反复跑）
+fn bench_once<F: FnOnce()>(label: &str, ops: usize, f: F) {
+    let t0 = Instant::now();
+    f();
+    let d = t0.elapsed();
+    let per = d.as_secs_f64() * 1e6 / ops as f64;
+    println!(
+        "{:<38} {:>9.2} ms {:>10.3} us/次",
+        label,
+        d.as_secs_f64() * 1e3,
+        per
+    );
+}
+
+/// 造一行
+fn row(id: i64) -> Row {
+    let mut m = Row::new();
+    m.insert("id".to_string(), json!(id));
+    m.insert("name".to_string(), json!(format!("user{}", id)));
+    m
+}
+
+/// 小随机数发生器，避免引 rand
+fn next_rand(state: &mut u64) -> u64 {
+    *state = state.wrapping_mul(6364136223846793005).wrapping_add(1442695040888963407);
+    *state >> 33
+}
+
+// 页 IO
+/// 顺序写 / 顺序读 / 随机读
+fn bench_page(dir: &std::path::Path, n: usize) {
+    let path = dir.join("page.db");
+    let mut pf = PageFile::with_options(&path, DEFAULT_PAGE_SIZE, 1024).unwrap();
+
+    bench("page 顺序写（含 flush）", n, 3, || {
+        pf.truncate().unwrap();
+        for i in 0..n {
+            pf.write_page(&Page::new(i as u64, DEFAULT_PAGE_SIZE)).unwrap();
+        }
+        pf.flush().unwrap();
+    });
+    drop(pf);
+
+    // 池子故意开小，让顺序读真的去读盘
+    let mut pf = PageFile::with_options(&path, DEFAULT_PAGE_SIZE, 16).unwrap();
+    bench("page 顺序读（池 16，基本都缺页）", n, 3, || {
+        for i in 0..n {
+            pf.read_page(i as u64).unwrap();
+        }
+    });
+
+    let mut pf = PageFile::with_options(&path, DEFAULT_PAGE_SIZE, 16).unwrap();
+    let mut state = 12345u64;
+    bench("page 随机读（池 16）", n, 3, || {
+        for _ in 0..n {
+            let id = next_rand(&mut state) % n as u64;
+            pf.read_page(id).unwrap();
+        }
+    });
+
+    // 池子开大、工作集比池子还大：每次缺页都要挑一个牺牲页
+    let mut pf = PageFile::with_options(&path, DEFAULT_PAGE_SIZE, 1024).unwrap();
+    let mut state = 999u64;
+    bench("page 随机读（池 1024，工作集 > 池）", n, 3, || {
+        for _ in 0..n {
+            let id = next_rand(&mut state) % n as u64;
+            pf.read_page(id).unwrap();
+        }
+    });
+    println!(
+        "  （池 1024：命中 {}/{})",
+        pf.hits(),
+        pf.hits() + pf.misses()
+    );
+}
+
+// B+ 树
+/// 插入、点查、全量遍历
+fn bench_btree(dir: &std::path::Path, n: usize) {
+    let path = dir.join("bt.idx");
+    let _ = std::fs::remove_file(&path);
+    let mut bt = DiskBTree::open(&path, DEFAULT_PAGE_SIZE, DEFAULT_BTREE_ORDER, 1024).unwrap();
+
+    bench("btree 插入（含 flush）", n, 2, || {
+        bt.clear().unwrap();
+        for i in 0..n {
+            bt.insert(i as i64, i as u64).unwrap();
+        }
+        bt.flush().unwrap();
+    });
+
+    bench("btree 点查（全部命中）", n, 3, || {
+        for i in 0..n {
+            bt.get(i as i64).unwrap().expect("key must exist");
+        }
+    });
+
+    bench("btree 全量遍历", n, 3, || {
+        let v = bt.iter_all().unwrap();
+        assert_eq!(v.len(), n);
+    });
+}
+
+// 堆表
+/// 插行、全表扫描、按索引取行
+fn bench_heap(dir: &std::path::Path, n: usize) {
+    let path = dir.join("heap.db");
+    let idx = dir.join("heap.idx");
+    let _ = std::fs::remove_file(&path);
+    let _ = std::fs::remove_file(&idx);
+    let mut t = HeapTable::open(&path, DEFAULT_PAGE_SIZE, 1024).unwrap();
+
+    bench("heap 插入（只在缓冲池，不 flush）", n, 2, || {
+        t.replace_all(&[]).unwrap();
+        for i in 0..n {
+            t.insert_row(&row(i as i64)).unwrap();
+        }
+    });
+
+    bench("heap 插入 + flush", n, 2, || {
+        t.replace_all(&[]).unwrap();
+        for i in 0..n {
+            t.insert_row(&row(i as i64)).unwrap();
+        }
+        t.flush().unwrap();
+    });
+
+    bench("heap 批量插入 + flush（一次落盘）", n, 2, || {
+        t.replace_all(&[]).unwrap();
+        let rows: Vec<Row> = (0..n as i64).map(row).collect();
+        t.insert_rows(&rows).unwrap();
+        t.flush().unwrap();
+    });
+
+    bench("heap 全表扫描", n, 3, || {
+        let rows = t.scan().unwrap();
+        assert_eq!(rows.len(), n);
+    });
+}
+
+// WAL
+/// 追加写与清空
+fn bench_wal(dir: &std::path::Path, n: usize) {
+    let path = dir.join("wal.log");
+    let _ = std::fs::remove_file(&path);
+    let wal = Wal::new(&path);
+    let op = WalOp::Insert {
+        table: "t".to_string(),
+        row: row(1),
+    };
+
+    bench_once("wal 追加（每条都 fsync）", n, || {
+        for _ in 0..n {
+            wal.append(&op).unwrap();
+        }
+    });
+    wal.clear().unwrap();
+
+    bench_once("wal 清空（每条都 fsync）", n, || {
+        for _ in 0..n {
+            wal.clear().unwrap();
+        }
+    });
+    wal.clear().unwrap();
+
+    bench_once("wal 截断（不落盘）", n, || {
+        for _ in 0..n {
+            wal.truncate().unwrap();
+        }
+    });
+
+    // 拆分：一次 fsync 本身多贵，一次 open 多贵
+    use std::fs::OpenOptions;
+    use std::io::Write;
+    // 大小和一条真实的 WAL 记录同量级（~200 字节）
+    let bytes = vec![0u8; 200];
+    bench_once("  └ open + write + fsync", n, || {
+        for _ in 0..n {
+            let mut f = OpenOptions::new()
+                .create(true)
+                .append(true)
+                .open(&path)
+                .unwrap();
+            f.write_all(&bytes).unwrap();
+            f.sync_data().unwrap();
+        }
+    });
+    let mut open_file = OpenOptions::new()
+        .create(true)
+        .append(true)
+        .open(&path)
+        .unwrap();
+    bench_once("  └ 复用句柄：write + fsync", n, || {
+        for _ in 0..n {
+            open_file.write_all(&bytes).unwrap();
+            open_file.sync_data().unwrap();
+        }
+    });
+    bench_once("  └ only fsync（不开不写）", n, || {
+        for _ in 0..n {
+            open_file.sync_data().unwrap();
+        }
+    });
+    bench_once("  └ only open/close", n, || {
+        for _ in 0..n {
+            let _ = OpenOptions::new()
+                .create(true)
+                .append(true)
+                .open(&path)
+                .unwrap();
+        }
+    });
+    wal.clear().unwrap();
+}
+
+// 服务端写入路径
+/// 复刻 server.rs 里 write_via_wal 的顺序：清 WAL -> 写 WAL -> 改数据 -> flush -> 清 WAL
+fn bench_write_path(dir: &std::path::Path, n: usize) {
+    let path = dir.join("wp.db");
+    let idx = dir.join("wp.idx");
+    let wal_path = dir.join("wp.wal");
+    let _ = std::fs::remove_file(&path);
+    let _ = std::fs::remove_file(&idx);
+    let _ = std::fs::remove_file(&wal_path);
+
+    let mut t = HeapTable::open_indexed(
+        &path,
+        &idx,
+        DEFAULT_PAGE_SIZE,
+        DEFAULT_BTREE_ORDER,
+        1024,
+    )
+    .unwrap();
+    let wal = Wal::new(&wal_path);
+
+    bench_once("写入路径 单条 INSERT（端到端）", n, || {
+        for i in 0..n as i64 {
+            wal.truncate().unwrap();
+            let op = WalOp::Insert {
+                table: "t".to_string(),
+                row: row(i),
+            };
+            wal.append(&op).unwrap();
+            t.insert_row(&row(i)).unwrap();
+            t.flush().unwrap();
+            wal.clear().unwrap();
+        }
+    });
+
+    // 拆开量，好定位时间花在哪一步
+    bench_once("  └ wal.truncate()（不落盘）", n, || {
+        for _ in 0..n {
+            wal.truncate().unwrap();
+        }
+    });
+
+    let op = WalOp::Insert {
+        table: "t".to_string(),
+        row: row(1),
+    };
+    bench_once("  └ wal.append()（含 fsync）", n, || {
+        for _ in 0..n {
+            wal.append(&op).unwrap();
+        }
+    });
+    wal.clear().unwrap();
+
+    bench_once("  └ wal.clear()（含 fsync）", n, || {
+        for _ in 0..n {
+            wal.clear().unwrap();
+        }
+    });
+
+    bench_once("  └ heap.insert_row()（含写索引）", n, || {
+        // 主循环已经插过 0..n 了，这里换个号段，免得撞上"索引列唯一"
+        for i in n as i64..2 * n as i64 {
+            t.insert_row(&row(i)).unwrap();
+        }
+    });
+
+    bench_once("  └ heap.flush()", n, || {
+        for _ in 0..n {
+            t.flush().unwrap();
+        }
+    });
+}
+
+fn main() {
+    let n: usize = std::env::var("CHUSQL_BENCH_N")
+        .ok()
+        .and_then(|v| v.parse().ok())
+        .unwrap_or(2000);
+
+    println!("chusql-storage 基准：n = {}，页大小 = {} 字节，btree order = {}",
+        n, DEFAULT_PAGE_SIZE, DEFAULT_BTREE_ORDER);
+    println!("每项取最快一轮；带 fsync 的项只跑一次（跑多了太慢）\n");
+
+    let dir = tempfile::tempdir().unwrap();
+
+    println!("[页 IO]");
+    bench_page(dir.path(), n);
+
+    println!("\n[B+ 树]");
+    bench_btree(dir.path(), n);
+
+    println!("\n[堆表]");
+    bench_heap(dir.path(), n);
+
+    println!("\n[WAL]");
+    bench_wal(dir.path(), n.min(200));
+
+    println!("\n[服务端写入路径]");
+    bench_write_path(dir.path(), n.min(200));
+}
diff --git a/benchmark/fullchain/chusql-fullchain.cabal b/benchmark/fullchain/chusql-fullchain.cabal
new file mode 100644
index 0000000..67bf3d1
--- /dev/null
+++ b/benchmark/fullchain/chusql-fullchain.cabal
@@ -0,0 +1,17 @@
+cabal-version: 2.4
+
+name:           chusql-fullchain
+version:        1.0.0
+synopsis:       ChuSQL 全链路基准：Haskell 引擎 + Rust 存储进程一起跑
+build-type:     Simple
+
+executable chusql-fullchain
+    main-is:          Main.hs
+    hs-source-dirs:   src
+    build-depends:    base >= 4.14 && < 5
+                    , chusql-engine
+                    , directory
+                    , filepath
+                    , process
+    default-language: Haskell2010
+    ghc-options:      -O2 -Wall
diff --git a/benchmark/fullchain/src/Main.hs b/benchmark/fullchain/src/Main.hs
new file mode 100644
index 0000000..b4ae703
--- /dev/null
+++ b/benchmark/fullchain/src/Main.hs
@@ -0,0 +1,435 @@
+module Main where
+
+import ChuSQL.Engine (runStatementM)
+import ChuSQL.Model (Row, Value (..))
+import ChuSQL.Storage (IndexResult (..))
+import ChuSQL.Storage.IPC (
+    IPCStorage (..),
+    Request (..),
+    Response (..),
+    TableInfo (..),
+    closeConnection,
+    doInsert,
+    doListCatalog,
+    doLookupByColumn,
+    sendRequest,
+ )
+import ChuSQL.Syntax.Parser (parseStatement)
+import Control.Concurrent (threadDelay)
+import Control.Exception (SomeException, bracket, evaluate, try)
+import Control.Monad (filterM, unless, when)
+import Data.List (intercalate, isInfixOf, isPrefixOf)
+import GHC.Clock (getMonotonicTime)
+import System.Directory (
+    createDirectoryIfMissing,
+    doesFileExist,
+    getTemporaryDirectory,
+    removeDirectoryRecursive,
+ )
+import System.Environment (getArgs, getEnvironment, setEnv)
+import System.Exit (exitFailure)
+import System.FilePath ((</>))
+import System.Process (
+    CreateProcess (..),
+    ProcessHandle,
+    StdStream (..),
+    createProcess,
+    proc,
+    terminateProcess,
+    waitForProcess,
+ )
+import Text.Printf (printf)
+
+-- 全链路基准：Haskell 引擎和 Rust 存储进程**一起启动**，跑真实情景。
+--
+-- 一条语句真正走过的路：
+--   SQL 文本 → 词法/语法分析 → 语义检查 → 关系代数 → 命名管道（JSON 行）
+--            → Rust：WAL（fsync）→ 堆表/B+ 树 → 页缓冲池 → 落盘
+--            → 结果原路返回
+--
+-- 计时用**墙上时钟（单调时钟）**，不是 CPU 时间：这条链路大部分工夫花在等 IO
+-- 和跨进程往返上，用 CPU 时间会把这些等待整个漏掉。
+--
+-- 跑法（先把 Rust 那边编译成 release）：
+--   cd chusql-storage && cargo build --release
+--   cd benchmark/fullchain && stack run              # 默认 users=orders=200
+--   stack run -- 500 500                             # 换规模
+--   stack run -- 200 200 ../../chusql-storage/target/release/server.exe   # 指定存储进程
+
+-- * 命令行与存储进程
+
+-- | 找 Rust 存储进程：优先 release，其次 debug
+findServer :: FilePath -> IO FilePath
+findServer "" = do
+    let dirs =
+            [ "chusql-storage/target"
+            , "../../chusql-storage/target"
+            , "../chusql-storage/target"
+            , "target"
+            ]
+        modes = ["release", "debug"]
+        exes = ["server.exe", "server"]
+        candidates = [d </> m </> e | d <- dirs, m <- modes, e <- exes]
+    found <- filterM doesFileExist candidates
+    case found of
+        (p : _) -> do
+            unless ("release" `isInfixOf` p) $
+                putStrLn "!! 找到的是 debug 版存储进程，数字会偏慢；建议 cargo build --release"
+            pure p
+        [] -> do
+            putStrLn "找不到 Rust 存储进程。先编译："
+            putStrLn "    cd chusql-storage && cargo build --release"
+            exitFailure
+findServer p = do
+    ok <- doesFileExist p
+    if ok
+        then pure p
+        else do
+            putStrLn ("指定的存储进程不存在：" ++ p)
+            exitFailure
+
+-- | 子进程环境：继承当前环境，但把 CHUSQL_* 换成本次专用的
+childEnv :: [(String, String)] -> IO [(String, String)]
+childEnv extra = do
+    base <- getEnvironment
+    let stripped = filter (\(k, _) -> not ("CHUSQL_" `isPrefixOf` k)) base
+    pure (stripped ++ extra)
+
+-- | 起存储进程并等管道可连
+startServer :: FilePath -> String -> FilePath -> IO ProcessHandle
+startServer serverPath pipe dataDir = do
+    envs <-
+        childEnv
+            [ ("CHUSQL_PIPE", pipe)
+            , ("CHUSQL_DATA_DIR", dataDir)
+            , ("CHUSQL_PAGE_SIZE", "4096")
+            , ("CHUSQL_BTREE_ORDER", "4")
+            , ("CHUSQL_LOG", "error")
+            ]
+    (_, _, _, ph) <-
+        createProcess
+            (proc serverPath []) {env = Just envs, std_out = NoStream, std_err = Inherit}
+    ready <- waitReady (200 :: Int)
+    unless ready $ do
+        putStrLn "存储进程 5 秒内没就绪"
+        exitFailure
+    pure ph
+
+-- | 轮询 ping，直到对面应答
+waitReady :: Int -> IO Bool
+waitReady 0 = pure False
+waitReady n = do
+    r <- try (sendRequest ReqPing) :: IO (Either SomeException Response)
+    case r of
+        Right RespPong -> pure True
+        _ -> threadDelay 25000 >> waitReady (n - 1)
+
+-- | 停存储进程并清掉缓存连接
+stopServer :: ProcessHandle -> FilePath -> IO ()
+stopServer ph dataDir = do
+    closeConnection
+    terminateProcess ph
+    _ <- waitForProcess ph
+    _ <- try (removeDirectoryRecursive dataDir) :: IO (Either SomeException ())
+    pure ()
+
+-- * 计时
+
+-- | 量一次墙上耗时，并把结果行数强制出来（Haskell 是惰性的，不强制就等于没测）
+timedRows :: IO (Either String [Row]) -> IO (Double, Either String Int)
+timedRows act = do
+    t0 <- getMonotonicTime
+    r <- act
+    n <- case r of
+        Left _ -> pure (-1)
+        Right rows -> evaluate (length rows)
+    t1 <- getMonotonicTime
+    pure (t1 - t0, either Left (const (Right n)) r)
+
+-- | 跑一条 SQL 文本（整条链路）
+runSql :: String -> IO (Either String [Row])
+runSql sql = case parseStatement sql of
+    Left e -> pure (Left e)
+    Right stmt -> runIPCStorage (runStatementM stmt)
+
+-- | 打印一行结果
+report :: String -> Either String Int -> Double -> IO ()
+report label result dt = case result of
+    Left e -> printf "%-38s %10s   !! %s\n" label "失败" e
+    Right n -> printf "%-38s %8.1f ms %8d 行\n" label (dt * 1000) n
+
+-- | 单独量一条 SQL（先预热一遍）：只适合可以重复跑的语句（SELECT）
+benchSql :: String -> String -> IO (Either String Int)
+benchSql label sql = do
+    _ <- runSql sql -- 预热：连接、页缓存、优化器都先热一次
+    (dt, r) <- timedRows (runSql sql)
+    report label r dt
+    pure r
+
+-- | 只跑一次的语句（CREATE TABLE 这类重跑会报错的）
+benchSqlOnce :: String -> String -> IO (Either String Int)
+benchSqlOnce label sql = do
+    (dt, r) <- timedRows (runSql sql)
+    report label r dt
+    pure r
+
+-- * 场景
+
+-- | 造一条 INSERT 的 SQL 文本
+userSql :: Int -> String
+userSql i =
+    printf "INSERT INTO users (id, name, age) VALUES (%d, 'user%d', %d)" i i (i `mod` 100)
+
+-- | 造一条订单的 INSERT
+orderSql :: Int -> Int -> String
+orderSql u j =
+    printf
+        "INSERT INTO orders (id, user_id, product) VALUES (%d, %d, 'item%d')"
+        j
+        (1 + (j - 1) `mod` u)
+        (j `mod` 50)
+
+-- | 批量插入并报平均耗时
+batchInsert :: String -> Int -> (Int -> String) -> IO (Either String ())
+batchInsert label n mkSql = do
+    t0 <- getMonotonicTime
+    results <- mapM (runSql . mkSql) [1 .. n]
+    t1 <- getMonotonicTime
+    let total = t1 - t0
+        errs = [e | Left e <- results]
+    case errs of
+        [] -> do
+            printf
+                "%-38s %8.1f ms %7.3f ms/条\n"
+                label
+                (total * 1000)
+                (total * 1000 / fromIntegral n)
+            pure (Right ())
+        (e : _) -> do
+            printf "%-38s %10s   !! %s\n" label "失败" e
+            pure (Left e)
+
+-- | 一次点查（原始 IPC，不经过引擎）
+benchLookup :: String -> String -> Int -> Int -> IO ()
+benchLookup table column key times = do
+    _ <- doLookupByColumn table column key
+    t0 <- getMonotonicTime
+    results <- mapM (const (doLookupByColumn table column key)) [1 .. times]
+    t1 <- getMonotonicTime
+    let total = t1 - t0
+        hit = length [() | Right (IndexRow (Just _)) <- results]
+    printf
+        "%-38s %8.1f ms %7.3f ms/次（命中 %d/%d）\n"
+        "lookup_by_index（原始 IPC，按 id）"
+        (total * 1000)
+        (total * 1000 / fromIntegral times)
+        hit
+        times
+
+-- | 量 list_catalog：现在每条语句都要先来一发（只取结构，不取行）
+benchListCatalog :: Int -> IO ()
+benchListCatalog n = do
+    t0 <- getMonotonicTime
+    _ <- mapM (const doListCatalog) [1 .. n]
+    t1 <- getMonotonicTime
+    let total = t1 - t0
+    printf
+        "%-38s %8.1f ms %7.3f ms/次\n"
+        "list_catalog（取结构）"
+        (total * 1000)
+        (total * 1000 / fromIntegral n)
+
+-- | 量原始 IPC 插入：不经过引擎，把"协议 + 存储"和"引擎"分开
+benchRawInsert :: String -> [Row] -> IO ()
+benchRawInsert table rows = do
+    t0 <- getMonotonicTime
+    results <- mapM (\r -> doInsert table r) rows
+    t1 <- getMonotonicTime
+    let total = t1 - t0
+        n = length rows
+        errs = [e | Left e <- results]
+    case errs of
+        [] ->
+            printf
+                "%-38s %8.1f ms %7.3f ms/条\n"
+                ("原始 IPC insert × " ++ show n)
+                (total * 1000)
+                (total * 1000 / fromIntegral n)
+        (e : _) -> printf "%-38s %10s   !! %s\n" "原始 IPC insert" "失败" e
+
+-- | 造一行 users 数据（给原始 IPC 用）
+userRow :: Int -> Row
+userRow i = [("id", VInt i), ("name", VStr ("user" ++ show i)), ("age", VInt (i `mod` 100))]
+
+-- | 依次跑一批语句，返回 (耗时秒, 错误清单)
+runBatch :: [String] -> IO (Double, [String])
+runBatch sqls = do
+    t0 <- getMonotonicTime
+    results <- mapM runSql sqls
+    t1 <- getMonotonicTime
+    pure (t1 - t0, [e | Left e <- results])
+
+-- | 把 1..n 按 size 切成一段段
+chunked :: Int -> Int -> [[Int]]
+chunked size n = go [1 .. n]
+  where
+    -- \| 每次切下 size 个
+    go [] = []
+    go xs = let (a, b) = splitAt size xs in a : go b
+
+-- | 一条带多行的 INSERT（一条语句 N 行，只落一次盘）
+multiInsertSql :: [Int] -> String
+multiInsertSql ids =
+    "INSERT INTO batch_t (id, name, age) VALUES "
+        ++ intercalate ", " [printf "(%d, 'b%d', %d)" i i (i `mod` 100) | i <- ids]
+
+-- | 打印一张表的统计
+printStats :: TableInfo -> IO ()
+printStats i =
+    printf
+        "  %-12s %6d 行  索引=%s\n             统计=%s\n"
+        (tiTable i)
+        (tiRows i)
+        (if null (tiIndexes i) then "无" else unwords (tiIndexes i))
+        ( unwords
+            [ n ++ ":" ++ show d ++ (if c then "+（下界）" else "")
+            | (n, d, c) <- tiStats i
+            ]
+        )
+
+-- | 主场景
+runScenarios :: Int -> Int -> IO ()
+runScenarios u o = do
+    putStrLn "\n[建表]"
+    r1 <- benchSqlOnce "CREATE TABLE users" "CREATE TABLE users (id int, name str, age int)"
+    r2 <- benchSqlOnce "CREATE TABLE orders" "CREATE TABLE orders (id int, user_id int, product str)"
+    case (r1, r2) of
+        (Right _, Right _) -> pure ()
+        _ -> do
+            putStrLn "建表失败，后面不用跑了"
+            exitFailure
+
+    putStrLn "\n[写入：每条 INSERT 都是一次完整落盘]"
+    _ <- batchInsert (printf "%d 条 INSERT INTO users" u) u userSql
+    _ <- batchInsert (printf "%d 条 INSERT INTO orders" o) o (orderSql u)
+
+    putStrLn "\n[分解：同一条 INSERT 拆成两半，都用原始 IPC，不经过引擎]"
+    _ <- benchSqlOnce "CREATE TABLE raw_users" "CREATE TABLE raw_users (id int, name str, age int)"
+    benchListCatalog 200
+    benchRawInsert "raw_users" [userRow i | i <- [1 .. u]]
+
+    putStrLn "\n[读取与查询：整条语句，含引擎侧的解析与语义检查]"
+    _ <- benchSql "SELECT * FROM users" "SELECT * FROM users"
+    ageR <- benchSql "SELECT name FROM users WHERE age > 90" "SELECT name FROM users WHERE age > 90"
+
+    putStrLn "\n[读取与查询：连接]"
+    joinR <-
+        benchSql
+            "JOIN + WHERE（哈希连接）"
+            "SELECT u.name FROM users u JOIN orders o ON u.id = o.user_id WHERE u.age > 90"
+
+    putStrLn "\n[点查]"
+    benchLookup "users" "id" (u `div` 2) 100
+    _ <- benchSql "SELECT ... WHERE id = k（走 Lookup）" (printf "SELECT name FROM users WHERE id = %d" (u `div` 2))
+
+    putStrLn "\n[批量插入：一条语句带多行，N 行只落一次盘]"
+    _ <- benchSqlOnce "CREATE TABLE batch_t" "CREATE TABLE batch_t (id int, name str, age int)"
+    let groups = chunked 100 u
+    (bt, batchErrs) <- runBatch (map multiInsertSql groups)
+    case batchErrs of
+        [] ->
+            printf
+                "%-38s %8.1f ms %7.3f ms/行（%d 行/条 × %d 条语句）\n"
+                "多行 INSERT"
+                (bt * 1000)
+                (bt * 1000 / fromIntegral u)
+                (100 :: Int)
+                (length groups)
+        (e : _) -> printf "%-38s %10s   !! %s\n" "多行 INSERT" "失败" e
+
+    putStrLn "\n[行级删除：代价和删几行无关，只和扫描 + 一次落盘有关]"
+    _ <- benchSqlOnce "DELETE FROM users WHERE id = k（1 行）" (printf "DELETE FROM users WHERE id = %d" (u `div` 2))
+    _ <- benchSqlOnce "DELETE FROM users（全部）" "DELETE FROM users"
+
+    putStrLn "\n[二级索引：没有索引回退扫描，建完索引走索引]"
+    _ <- benchSqlOnce "CREATE TABLE items" "CREATE TABLE items (id int, code int)"
+    let itemGroups = chunked 100 o
+        itemSql ids =
+            "INSERT INTO items (id, code) VALUES "
+                ++ intercalate ", " [printf "(%d, %d)" i (i * 7 + 1) | i <- ids]
+    (it, itemErrs) <- runBatch (map itemSql itemGroups)
+    case itemErrs of
+        [] -> pure ()
+        (e : _) -> printf "  !! %s\n" e
+    printf "  （先把 %d 行灌进 items：%.1f ms）\n" o (it * 1000)
+    let targetCode = (o `div` 2) * 7 + 1
+    _ <-
+        benchSql
+            "SELECT ... WHERE code = k（无索引）"
+            (printf "SELECT id FROM items WHERE code = %d" targetCode)
+    _ <- benchSqlOnce "CREATE INDEX ON items (code)" "CREATE INDEX ON items (code)"
+    _ <-
+        benchSql
+            "SELECT ... WHERE code = k（走索引）"
+            (printf "SELECT id FROM items WHERE code = %d" targetCode)
+
+    putStrLn "\n[数据字典统计]"
+    cat <- doListCatalog
+    case cat of
+        Left e -> printf "  取统计失败：%s\n" e
+        Right infos -> mapM_ printStats infos
+
+    putStrLn "\n[校验]"
+    let expectAge = 9 * (u `div` 100) + max 0 (u `mod` 100 - 90)
+    printf
+        "age > 90 命中 %s（按数据分布应为 %d 行）\n"
+        (either show show ageR)
+        expectAge
+    when (u == o) $
+        printf
+            "JOIN 命中 %s（每个用户恰好 1 张订单，应与上一行相同 = %d）\n"
+            (either show show joinR)
+            expectAge
+    unless (u == o) $
+        putStrLn "（users 与 orders 行数不同，JOIN 行数没有简单公式，只打印不校验）"
+    printf "多行 INSERT 灌进去 %d 行（应为 %d）\n" u u
+    printf "二级索引那一行：code = %d 应该查到 id = %d\n" targetCode (o `div` 2)
+
+-- | 主入口
+main :: IO ()
+main = do
+    args <- getArgs
+    let pick i d = if length args > i then args !! i else d
+        u = read (pick 0 "200") :: Int
+        o = read (pick 1 "200") :: Int
+        serverArg = pick 2 ""
+    serverPath <- findServer serverArg
+
+    -- 每次跑用独立的管道名与数据目录，避免和别的进程抢
+    tmp <- getTemporaryDirectory
+    stamp <- getMonotonicTime
+    let pipe = "chusql-fullchain-" ++ show (round (stamp * 1e6) :: Int)
+        dataDir = tmp </> pipe
+    createDirectoryIfMissing True dataDir
+    setEnv "CHUSQL_PIPE" pipe
+
+    printf "全链路基准：Haskell 引擎 ←命名管道→ Rust 存储进程\n"
+    printf "存储进程：%s\n" serverPath
+    printf "管道：%s\n" pipe
+    printf "数据目录：%s\n" dataDir
+    printf "数据规模：users = %d 行，orders = %d 行\n" u o
+    printf "计时：墙上时钟（单调）；每条语句都走完整链路\n"
+
+    bracket
+        (do
+            t1 <- getMonotonicTime
+            ph <- startServer serverPath pipe dataDir
+            t2 <- getMonotonicTime
+            printf "\n[启动] 存储进程就绪，用时 %.2f s\n" (t2 - t1)
+            pure ph
+        )
+        (\ph -> do
+            putStrLn "\n[收尾] 停存储进程、清理数据目录"
+            stopServer ph dataDir
+        )
+        (const (runScenarios u o))
diff --git a/benchmark/fullchain/stack.yaml b/benchmark/fullchain/stack.yaml
new file mode 100644
index 0000000..eacce59
--- /dev/null
+++ b/benchmark/fullchain/stack.yaml
@@ -0,0 +1,5 @@
+resolver: lts-24.59
+
+packages:
+    - .
+    - ../../chusql-engine
diff --git a/benchmark/fullchain/stack.yaml.lock b/benchmark/fullchain/stack.yaml.lock
new file mode 100644
index 0000000..e3f9041
--- /dev/null
+++ b/benchmark/fullchain/stack.yaml.lock
@@ -0,0 +1,12 @@
+# This file was autogenerated by Stack.
+# You should not edit this file by hand.
+# For more information, please see the documentation at:
+#   https://docs.haskellstack.org/en/stable/topics/lock_files
+
+packages: []
+snapshots:
+- completed:
+    sha256: 0f728e30e843d7f00460ad56858b995a3b227fca683659c7df9f2fc3988a3ce1
+    size: 732465
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/24/59.yaml
+  original: lts-24.59
diff --git a/chusql-engine/chusql-engine.cabal b/chusql-engine/chusql-engine.cabal
index f1f839c..9d4a8a9 100644
--- a/chusql-engine/chusql-engine.cabal
+++ b/chusql-engine/chusql-engine.cabal
@@ -26,10 +26,12 @@ library
     build-depends:    base >= 4.14 && < 5
                     , aeson
                     , bytestring
+                    , hashable
                     , megaparsec
                     , parser-combinators
                     , scientific
                     , text
+                    , unordered-containers
     default-language: Haskell2010
     ghc-options:      -Wall
 
diff --git a/chusql-engine/src/ChuSQL/Algebra/Eval.hs b/chusql-engine/src/ChuSQL/Algebra/Eval.hs
index 9db8993..6221f53 100644
--- a/chusql-engine/src/ChuSQL/Algebra/Eval.hs
+++ b/chusql-engine/src/ChuSQL/Algebra/Eval.hs
@@ -4,9 +4,10 @@ import ChuSQL.Algebra.Expr (evalCondForRow)
 import ChuSQL.Algebra.Op
 import ChuSQL.Algebra.Sort (sortRows)
 import ChuSQL.Model
-import ChuSQL.Storage (MonadStorage (..))
+import ChuSQL.Storage (IndexResult (..), MonadStorage (..))
 import ChuSQL.Syntax.AST (Expr (..))
 import Control.Monad (filterM, foldM)
+import qualified Data.HashMap.Strict as HM
 
 -- 执行：按算子树算出结果行（Scan 阶段会加别名前缀）。
 
@@ -18,19 +19,55 @@ project ["*"] row = row
 project cs row = [(c, v) | (c, v) <- row, c `elem` cs]
 
 -- | 给列名加别名前缀
-addPrefix :: String -> Row -> Row
-addPrefix prefix = map (\(k, v) -> (prefix ++ k, v))
-
--- | 主键匹配条件（id = k）
-keyCondition :: Int -> Expr
-keyCondition k = Eq (Col "id") (LitInt k)
+addPrefix :: Maybe String -> Row -> Row
+addPrefix mAlias = map (\(k, v) -> (qualify mAlias k, v))
 
 -- | 扫描一张表
 evalScan :: Database -> Maybe String -> String -> Either String [Row]
 evalScan db mAlias tbl = do
     table <- lookupTable db tbl
-    let prefix = maybe "" (++ ".") mAlias
-    Right (map (addPrefix prefix) (tableRows table))
+    Right (map (addPrefix mAlias) (tableRows table))
+
+-- | 点查退化成"扫描 + 按条件筛"时用的条件：`列 = 值`（列名带上别名前缀）
+lookupCondition :: Maybe String -> String -> Int -> Expr
+lookupCondition mAlias col k = Eq (Col (qualify mAlias col)) (LitInt k)
+
+-- * 等值连接
+
+-- | 等值连接的两侧键：左行取哪列、右行取哪列
+data EquiKeys = EquiKeys
+    { ekLeft :: String
+    , ekRight :: String
+    }
+
+-- | 一批行的列名（空批给空清单，此时一律退回嵌套循环）
+rowsCols :: [Row] -> [String]
+rowsCols (r : _) = map fst r
+rowsCols [] = []
+
+-- | 认出 a = b 这种两列等值条件，并且能分清谁在左谁在右
+equiKeys :: [Row] -> [Row] -> Expr -> Maybe EquiKeys
+equiKeys lrows rrows (Eq (Col a) (Col b))
+    | a /= b, a `elem` lcols, b `elem` rcols = Just (EquiKeys a b)
+    | a /= b, b `elem` lcols, a `elem` rcols = Just (EquiKeys b a)
+  where
+    lcols = rowsCols lrows
+    rcols = rowsCols rrows
+equiKeys _ _ _ = Nothing
+
+-- | 哈希连接：右表建哈希表，左表逐行探测。
+-- 输出顺序与嵌套循环一致（左表顺序为主，右表顺序为辅）。
+hashJoin :: EquiKeys -> [Row] -> [Row] -> [Row]
+hashJoin keys lrows rrows = concatMap probe lrows
+  where
+    -- 同一键的右行按原顺序排在桶里
+    buckets =
+        HM.fromListWith
+            (flip (++))
+            [(v, [r]) | r <- rrows, Just v <- [lookup (ekRight keys) r]]
+    probe l = case lookup (ekLeft keys) l of
+        Nothing -> []
+        Just v -> [l ++ r | r <- HM.lookupDefault [] v buckets]
 
 -- | 把两边的行按条件配对（边配边筛，不先建整张积表）
 filterPairs :: (Row -> Either String Bool) -> [Row] -> [Row] -> Either String [Row]
@@ -45,14 +82,21 @@ filterPairs cond lrows rrows = go lrows []
         ok <- cond row
         pure (if ok then row : acc else acc)
 
+-- | 一次连接：能认出等值键就走哈希，否则退回嵌套循环
+joinRows :: Expr -> [Row] -> [Row] -> Either String [Row]
+joinRows cond lrows rrows = case equiKeys lrows rrows cond of
+    Just keys -> Right (hashJoin keys lrows rrows)
+    Nothing -> filterPairs (evalCondForRow cond) lrows rrows
+
 -- * 求值
 
 -- | 纯求值（不需要存储）
 evalRelOp :: Database -> RelOp -> Either String [Row]
 evalRelOp db (Scan mAlias tbl) = evalScan db mAlias tbl
-evalRelOp db (Lookup tbl k) = do
-    rows <- evalScan db Nothing tbl
-    filterM (evalCondForRow (keyCondition k)) rows
+-- 纯求值没有索引可问：退回"扫描 + 按条件筛"，和未优化时的 Filter 完全等价
+evalRelOp db (Lookup mAlias tbl col k) = do
+    rows <- evalScan db mAlias tbl
+    filterM (evalCondForRow (lookupCondition mAlias col k)) rows
 evalRelOp db (Filter e op) = do
     rows <- evalRelOp db op
     filterM (evalCondForRow e) rows
@@ -68,9 +112,9 @@ evalRelOp db (Limit n op) = do
 evalRelOp db (Join left right cond) = do
     lrows <- evalRelOp db left
     rrows <- evalRelOp db right
-    filterPairs (evalCondForRow cond) lrows rrows
+    joinRows cond lrows rrows
 
--- | 单子求值：Lookup 问存储
+-- | 单子求值：Lookup 先问存储有没有索引，没有就退回扫描
 evalRelOpM :: (MonadStorage m) => RelOp -> m (Either String [Row])
 evalRelOpM (Scan mAlias t) = do
     result <- scan t
@@ -78,13 +122,19 @@ evalRelOpM (Scan mAlias t) = do
         rows <- result
         case mAlias of
             Nothing -> Right rows
-            Just a -> Right (map (addPrefix (a ++ ".")) rows)
-evalRelOpM (Lookup t k) = do
-    result <- lookupByKey t k
-    pure $ case result of
-        Left e -> Left e
-        Right Nothing -> Right []
-        Right (Just row) -> Right [row]
+            Just _ -> Right (map (addPrefix mAlias) rows)
+evalRelOpM (Lookup mAlias t col k) = do
+    result <- lookupByColumn t col k
+    case result of
+        Left e -> pure (Left e)
+        -- 这个列上没有索引：老老实实扫一遍（结果和未优化时一样）
+        Right NoIndex -> do
+            rows <- evalRelOpM (Scan mAlias t)
+            pure $ do
+                rs <- rows
+                filterM (evalCondForRow (lookupCondition mAlias col k)) rs
+        Right (IndexRow Nothing) -> pure (Right [])
+        Right (IndexRow (Just row)) -> pure (Right [addPrefix mAlias row])
 evalRelOpM (Filter p x) = do
     result <- evalRelOpM x
     pure $ do
@@ -105,4 +155,4 @@ evalRelOpM (Join l r cond) = do
     pure $ do
         left <- ls
         right <- rs
-        filterPairs (evalCondForRow cond) left right
+        joinRows cond left right
diff --git a/chusql-engine/src/ChuSQL/Algebra/Op.hs b/chusql-engine/src/ChuSQL/Algebra/Op.hs
index b5bd289..0f1602a 100644
--- a/chusql-engine/src/ChuSQL/Algebra/Op.hs
+++ b/chusql-engine/src/ChuSQL/Algebra/Op.hs
@@ -7,7 +7,11 @@ import ChuSQL.Syntax.AST (Expr, SortDir)
 -- | 算子树的一个节点
 data RelOp
     = Scan (Maybe String) String
-    | Lookup String Int
+    | -- \| 按某一列的值点查一行：别名、表、列、值。
+      -- 只是"这里可以走点查"的意思，到底有没有索引由存储层回答
+      -- （那个列上没有索引就退回全表扫描，见 Eval）。
+      -- 别名要留着，回来的一行才能和 `Scan 别名 表` 长得一样。
+      Lookup (Maybe String) String String Int
     | Filter Expr RelOp
     | Project [String] RelOp
     | Sort [(String, SortDir)] RelOp
@@ -21,7 +25,7 @@ renderPlan = go 0
   where
     go ind op = case op of
         Scan a t -> pad ++ "Scan " ++ show a ++ " " ++ show t
-        Lookup t k -> pad ++ "Lookup " ++ show t ++ " " ++ show k
+        Lookup _ t c k -> pad ++ "Lookup " ++ show t ++ "." ++ show c ++ " = " ++ show k
         Filter e x -> pad ++ "Filter " ++ show e ++ "\n" ++ go (ind + 1) x
         Project c x -> pad ++ "Project " ++ show c ++ "\n" ++ go (ind + 1) x
         Sort s x -> pad ++ "Sort " ++ show s ++ "\n" ++ go (ind + 1) x
diff --git a/chusql-engine/src/ChuSQL/Algebra/Optimize.hs b/chusql-engine/src/ChuSQL/Algebra/Optimize.hs
index 9033b36..bd9f1df 100644
--- a/chusql-engine/src/ChuSQL/Algebra/Optimize.hs
+++ b/chusql-engine/src/ChuSQL/Algebra/Optimize.hs
@@ -16,7 +16,7 @@ relOpCols db (Scan mAlias tbl) =
         Just t -> map (prefix ++) (colNames t)
   where
     prefix = maybe "" (++ ".") mAlias
-relOpCols db (Lookup tbl _) = relOpCols db (Scan Nothing tbl)
+relOpCols db (Lookup mAlias tbl _ _) = relOpCols db (Scan mAlias tbl)
 relOpCols db (Filter _ x) = relOpCols db x
 relOpCols _ (Project ["*"] _) = ["*"]
 relOpCols _ (Project cols _) = cols
@@ -104,7 +104,7 @@ pushProject db need (Join l r c)
             rNeed = if needsAll rCols then ["*"] else [x | x <- tot, x `elem` rCols]
          in Join (pushProject db lNeed l) (pushProject db rNeed r) c
 pushProject db need leaf@(Scan _ _) = pushProjectLeaf db need leaf
-pushProject db need leaf@(Lookup _ _) = pushProjectLeaf db need leaf
+pushProject db need leaf@(Lookup _ _ _ _) = pushProjectLeaf db need leaf
 
 
 -- * 常量折叠
@@ -131,8 +131,12 @@ foldConstants e = e
 -- * 执行优化
 -- | 单节点重写
 rewriteNode :: Database -> RelOp -> RelOp
-rewriteNode _ (Filter (Eq (Col k) (LitInt v)) (Scan _ t))
-    | k == "id" = Lookup t v
+-- 单列等值条件改成点查：这里是"可以走索引"的意思，
+-- 到底走不走得成由存储层回答（这个列上没有索引就退回全表扫描，见 Eval），
+-- 所以优化器不必先知道表上到底有哪些索引。
+-- 别名要留在节点里：回来的一行必须和 `Scan 别名 表` 长得一样，不然后面取列就对不上了。
+rewriteNode _ (Filter (Eq (Col k) (LitInt v)) (Scan mAlias t)) =
+    Lookup mAlias t (unqualify mAlias k) v
 rewriteNode db (Filter p (Join l r c)) = pushJoin db p l r c
 rewriteNode db (Filter p x) = case foldConstants p of
     LitBool True -> x
diff --git a/chusql-engine/src/ChuSQL/Engine.hs b/chusql-engine/src/ChuSQL/Engine.hs
index 892fab5..c5c25f1 100644
--- a/chusql-engine/src/ChuSQL/Engine.hs
+++ b/chusql-engine/src/ChuSQL/Engine.hs
@@ -9,7 +9,6 @@ import ChuSQL.Semantic (check)
 import ChuSQL.Storage (MonadStorage (..))
 import ChuSQL.Storage.Memory (MemoryStorage (runMemoryStorage))
 import ChuSQL.Syntax.AST
-import Control.Monad (filterM)
 
 -- 引擎入口：语义检查 + 分发执行，以及内存实现与泛型版本。
 
@@ -29,7 +28,9 @@ rowsOf = fmap snd
 -- | 泛型入口：先检查再执行
 runStatementM :: (MonadStorage m) => Statement -> m (Either String [Row])
 runStatementM q = do
-    db <- snapshot
+    -- 只要结构：语义检查和查询优化都只看列，一行数据都不碰，
+    -- 所以这里不用取整库快照（那会把所有行拉一遍）
+    db <- schema
     case check db q of
         Left err -> pure (Left err)
         Right _ -> runStatementUncheckedM db q
@@ -42,36 +43,43 @@ runStatementUncheckedM db q@Select{} =
     case translate q of
         Left e -> pure (Left e)
         Right relOp -> evalRelOpM (optimize db relOp)
-runStatementUncheckedM _ (Insert tbl cols vals) =
-    case mapM (\e -> evalExpr e []) vals of
+runStatementUncheckedM _ (Insert tbl cols rows) =
+    -- 多行一次交给存储：N 行只落一次盘（键怎么算、索引怎么写是存储层的事）
+    case mapM toRow rows of
         Left err -> pure (Left err)
-        Right values
-            | length cols /= length values ->
-                pure (Left "column count does not match value count")
-            | otherwise -> do
-                let row = zip cols values
-                    key = case lookup "id" row of
-                        Just (VInt k) -> Just k
-                        _ -> Nothing
-                result <- insert tbl row key
-                pure (result >> Right [])
+        Right rs -> do
+            result <- insertMany tbl rs
+            pure (result >> Right [])
+  where
+    -- \| 一行字面量求值成一行数据
+    toRow :: [Expr] -> Either String Row
+    toRow vals = do
+        values <- mapM (\e -> evalExpr e []) vals
+        if length cols /= length values
+            then Left "column count does not match value count"
+            else Right (zip cols values)
 runStatementUncheckedM _ (Delete tbl mWhere) = do
     rowsResult <- scan tbl
     case rowsResult of
         Left err -> pure (Left err)
-        Right rows -> do
-            let kept = case mWhere of
-                    Nothing -> Right []
-                    Just e -> filterM (shouldKeep e) rows
-            case kept of
-                Left err -> pure (Left err)
-                Right keptRows -> do
-                    result <- replaceAll tbl keptRows
-                    pure (result >> Right [])
+        Right rows -> case splitByCondition mWhere rows of
+            Left err -> pure (Left err)
+            Right (doomed, kept) ->
+                -- 要删的行都有 id 就走行级删（存储层原地删，代价只和删几行有关）；
+                -- 没有 id 的表定位不到行，只能整表写回。
+                case mapM rowId doomed of
+                    Right ids -> do
+                        result <- deleteKeys tbl ids
+                        pure (result >> Right [])
+                    Left _ -> do
+                        result <- replaceAll tbl kept
+                        pure (result >> Right [])
   where
-    -- \| 保留 = 条件不成立
-    shouldKeep :: Expr -> Row -> Either String Bool
-    shouldKeep e row = not <$> evalCondForRow e row
+    -- \| 这一行的 id（要拿来当删除键）
+    rowId :: Row -> Either String Int
+    rowId r = case lookup "id" r of
+        Just (VInt k) -> Right k
+        _ -> Left "row has no integer id"
 runStatementUncheckedM _ (Update tbl assigns mWhere) = do
     rowsResult <- scan tbl
     case rowsResult of
@@ -97,9 +105,27 @@ runStatementUncheckedM _ (CreateTable name cols) = do
 runStatementUncheckedM _ (DropTable name) = do
     result <- dropTable name
     pure (result >> Right [])
+runStatementUncheckedM _ (CreateIndex tbl col) = do
+    result <- createIndex tbl col
+    pure (result >> Right [])
+runStatementUncheckedM _ (DropIndex tbl col) = do
+    result <- dropIndex tbl col
+    pure (result >> Right [])
 
 -- * 更新辅助
 
+-- | 按条件把行分成"要删的"和"留着的"两拨（没有条件就全都要删）
+splitByCondition :: Maybe Expr -> [Row] -> Either String ([Row], [Row])
+splitByCondition cond = go [] []
+  where
+    -- \| 一行一行过，保持原顺序；条件求值出错就立刻停（和 filterM 一样）
+    go doomed kept [] = Right (reverse doomed, reverse kept)
+    go doomed kept (r : rs) = do
+        hit <- case cond of
+            Nothing -> Right True
+            Just e -> evalCondForRow e r
+        go (if hit then r : doomed else doomed) (if hit then kept else r : kept) rs
+
 -- | 依次求值并覆盖列
 applyUpdates :: [(String, Expr)] -> Row -> Either String Row
 applyUpdates [] row = Right row
diff --git a/chusql-engine/src/ChuSQL/Model.hs b/chusql-engine/src/ChuSQL/Model.hs
index 6f6de07..e1f7d59 100644
--- a/chusql-engine/src/ChuSQL/Model.hs
+++ b/chusql-engine/src/ChuSQL/Model.hs
@@ -1,4 +1,8 @@
-module ChuSQL.Model (Column (..), Value (..), Row, Table (..), Database, colNames, colType, lookupTable, allColumns) where
+module ChuSQL.Model (Column (..), Value (..), Row, Table (..), Database, colNames, colType, lookupTable, allColumns, qualify, unqualify) where
+
+import Data.Hashable (Hashable (..))
+import Data.List (stripPrefix)
+import Data.Maybe (fromMaybe)
 
 -- 数据模型：列类型、值、行、表、数据库，外加几个查表小工具。
 
@@ -17,6 +21,12 @@ data Value
     | VBool Bool
     deriving (Show, Eq)
 
+-- | 值要能当哈希键用（等值连接建哈希表）
+instance Hashable Value where
+    hashWithSalt s (VInt n) = hashWithSalt (hashWithSalt s (0 :: Int)) n
+    hashWithSalt s (VStr t) = hashWithSalt (hashWithSalt s (1 :: Int)) t
+    hashWithSalt s (VBool b) = hashWithSalt (hashWithSalt s (2 :: Int)) b
+
 -- | 一行：列名 -> 值
 type Row = [(String, Value)]
 
@@ -47,3 +57,13 @@ lookupTable db t = maybe (Left ("unknown table: " ++ t)) Right (lookup t db)
 -- | 投影哨兵 "*"
 allColumns :: String
 allColumns = "*"
+
+-- | 给列名加别名前缀：`Just "u"` + `name` -> `u.name`（没有别名就原样）
+qualify :: Maybe String -> String -> String
+qualify Nothing c = c
+qualify (Just a) c = a ++ "." ++ c
+
+-- | 去掉别名前缀：`Just "u"` + `u.name` -> `name`（没有这个前缀就原样返回）
+unqualify :: Maybe String -> String -> String
+unqualify Nothing c = c
+unqualify (Just a) c = fromMaybe c (stripPrefix (a ++ ".") c)
diff --git a/chusql-engine/src/ChuSQL/Semantic.hs b/chusql-engine/src/ChuSQL/Semantic.hs
index e7cd7fd..bc2b097 100644
--- a/chusql-engine/src/ChuSQL/Semantic.hs
+++ b/chusql-engine/src/ChuSQL/Semantic.hs
@@ -114,10 +114,12 @@ check db q = case q of
             checkColumns "SELECT" env cols
             checkColumns "ORDER BY" env (map fst orderBy)
             mapM_ (checkBool "WHERE" env) mWhere
-    Insert tbl cols vals -> do
+    Insert tbl cols rows -> do
         t <- lookupTable db tbl
         checkColumns "INSERT" (tableCols t) cols
-        mapM_ (checkValue t) (zip cols vals)
+        if null rows
+            then Left "INSERT: no values"
+            else mapM_ (mapM_ (checkValue t) . zip cols) rows
     Delete tbl mWhere -> do
         t <- lookupTable db tbl
         mapM_ (checkBool "WHERE" (tableCols t)) mWhere
@@ -138,3 +140,16 @@ check db q = case q of
         if null name
             then Left "DROP TABLE: empty table name"
             else Right ()
+    CreateIndex tbl col -> do
+        t <- lookupTable db tbl
+        if col `elem` tableCols' t
+            then Right ()
+            else Left ("CREATE INDEX: unknown column: " ++ col)
+    DropIndex tbl col -> do
+        t <- lookupTable db tbl
+        if col `elem` tableCols' t
+            then Right ()
+            else Left ("DROP INDEX: unknown column: " ++ col)
+  where
+    -- \| 表的列名清单
+    tableCols' = map fst . tableCols
diff --git a/chusql-engine/src/ChuSQL/Storage.hs b/chusql-engine/src/ChuSQL/Storage.hs
index b06a0e5..0530e7d 100644
--- a/chusql-engine/src/ChuSQL/Storage.hs
+++ b/chusql-engine/src/ChuSQL/Storage.hs
@@ -1,24 +1,66 @@
 module ChuSQL.Storage (
     MonadStorage (..),
+    IndexResult (..),
 ) where
 
-import ChuSQL.Model (Column, Database, Row)
+import ChuSQL.Model (Column, Database, Row, Table (..), Value (..))
 
 -- 存储层抽象：上层只认 domain 类型，不关心底层实现。
 
--- | 存储接口：读写表、按主键取行、取快照
+-- | 一次索引点查的结果
+data IndexResult
+    = -- \| 有索引，查过了：Just 命中一行，Nothing 没这行
+      IndexRow (Maybe Row)
+    | -- \| 没有这个索引 —— 调用方应该退回全表扫描
+      NoIndex
+    deriving (Show, Eq)
+
+-- | 存储接口：读写表、按索引取行、取快照
 class (Monad m) => MonadStorage m where
     -- \| 全表扫描
     scan :: String -> m (Either String [Row])
 
-    -- \| 追加一行
-    insert :: String -> Row -> Maybe Int -> m (Either String ())
+    -- \| 追加一行。
+    -- 要写哪些索引由**存储层按自己的元数据**决定（表上有哪些索引它自己清楚），
+    -- 调用方不需要指定 key。
+    insert :: String -> Row -> m (Either String ())
+
+    -- \| 一批行一起追加。
+    -- 默认逐行调 `insert`；能批量的实现（比如走 WAL 的 IPC 存储）会覆盖它，
+    -- 好处是 N 行只落一次盘。
+    insertMany :: String -> [Row] -> m (Either String ())
+    insertMany t = go
+      where
+        -- \| 一行一行来，遇到错就停
+        go [] = pure (Right ())
+        go (r : rs) = do
+            x <- insert t r
+            case x of
+                Left e -> pure (Left e)
+                Right _ -> go rs
+
+    -- \| 按 `id` 批量删行。
+    -- 默认实现是"全读出来、筛掉、整表写回"（对内存实现足够）；
+    -- 真正能在原地删的实现会覆盖它。
+    deleteKeys :: String -> [Int] -> m (Either String ())
+    deleteKeys t ks = do
+        rows <- scan t
+        case rows of
+            Left e -> pure (Left e)
+            Right rs -> replaceAll t [r | r <- rs, not (doomed r)]
+      where
+        -- \| 这一行的 id 在待删清单里吗
+        doomed r = case lookup "id" r of
+            Just (VInt k) -> k `elem` ks
+            _ -> False
 
     -- \| 整表替换
     replaceAll :: String -> [Row] -> m (Either String ())
 
-    -- \| 按主键取一行
-    lookupByKey :: String -> Int -> m (Either String (Maybe Row))
+    -- \| 按某一列的索引取一行。
+    -- 默认回答"没有索引"（内存实现不需要索引），于是上层会自己扫一遍。
+    lookupByColumn :: String -> String -> Int -> m (Either String IndexResult)
+    lookupByColumn _ _ _ = pure (Right NoIndex)
 
     -- \| 建一张空表
     createTable :: String -> [(String, Column)] -> m (Either String ())
@@ -26,5 +68,24 @@ class (Monad m) => MonadStorage m where
     -- \| 删除表
     dropTable :: String -> m (Either String ())
 
-    -- \| 取全库快照
+    -- \| 给某一列建索引（要求这一列整数取值唯一）
+    createIndex :: String -> String -> m (Either String ())
+    createIndex _ _ = pure (Right ())
+
+    -- \| 去掉某一列的索引
+    dropIndex :: String -> String -> m (Either String ())
+    dropIndex _ _ = pure (Right ())
+
+    -- \| 取全库快照（表名 + 列 + 全部行）
     snapshot :: m Database
+
+    -- \| 取全库**结构**：只要表名和列，不要行。
+    --
+    -- 语义检查和查询优化都只看列名/列类型，一行数据都不碰；
+    -- 而"取全库快照"要把所有行拉一遍，在单语句路径上是白花的钱。
+    -- 默认实现退化成整库快照再抹掉行，有更便宜做法的实现（比如走数据字典）可以覆盖。
+    schema :: m Database
+    schema = fmap (map withoutRows) snapshot
+      where
+        -- \| 抹掉行，只留表名与列定义
+        withoutRows (name, t) = (name, t {tableRows = []})
diff --git a/chusql-engine/src/ChuSQL/Storage/IPC.hs b/chusql-engine/src/ChuSQL/Storage/IPC.hs
index 3f31e00..b5574ba 100644
--- a/chusql-engine/src/ChuSQL/Storage/IPC.hs
+++ b/chusql-engine/src/ChuSQL/Storage/IPC.hs
@@ -6,11 +6,14 @@ module ChuSQL.Storage.IPC (
     Request (..),
     Response (..),
     SchemaColumn (..),
+    TableInfo (..),
     sendRequest,
     closeConnection,
     doListTables,
-    doLookupByKey,
-    doInsertWith,
+    doLookupByColumn,
+    doInsert,
+    doInsertMany,
+    doDeleteKeys,
     doDescribeTable,
     doDropTable,
     doListCatalog,
@@ -20,7 +23,7 @@ import ChuSQL.Model
 import ChuSQL.Storage
 import Control.Concurrent.MVar (MVar, modifyMVar, modifyMVar_, newMVar)
 import Control.Exception (IOException, try)
-import Data.Aeson (FromJSON (..), ToJSON (..), eitherDecodeStrict, encode, object, withObject, (.:), (.=))
+import Data.Aeson (FromJSON (..), ToJSON (..), eitherDecodeStrict, encode, object, withObject, (.:), (.:?), (.!=), (.=))
 import Data.Aeson qualified as A
 import Data.Aeson.Key qualified as K
 import Data.Aeson.KeyMap qualified as KM
@@ -155,28 +158,41 @@ instance FromJSON SchemaColumn where
 data Request
     = ReqPing
     | ReqScan String
-    | ReqInsert String Row (Maybe Int)
+    | ReqInsert String Row
+    | ReqInsertBatch String [Row]
+    | ReqDeleteKeys String [Int]
     | ReqReplaceAll String [Row]
     | ReqListTables
-    | ReqLookupByKey String Int
+    | ReqLookupByColumn String String Int
     | ReqDescribeTable String
     | ReqCreateTable String [SchemaColumn]
     | ReqDropTable String
+    | ReqCreateIndex String String
+    | ReqDropIndex String String
     | ReqListCatalog
 
 -- | 请求编码
 instance ToJSON Request where
     toJSON ReqPing = object ["method" .= ("ping" :: T.Text)]
     toJSON (ReqScan t) = object ["method" .= ("scan" :: T.Text), "table" .= t]
-    toJSON (ReqInsert t r mk) =
-        object $
+    toJSON (ReqInsert t r) =
+        object
             [ "method" .= ("insert" :: T.Text)
             , "table" .= t
             , "row" .= rowToJSON r
             ]
-                ++ case mk of
-                    Nothing -> []
-                    Just k -> ["key" .= k]
+    toJSON (ReqInsertBatch t rs) =
+        object
+            [ "method" .= ("insert_batch" :: T.Text)
+            , "table" .= t
+            , "rows" .= map rowToJSON rs
+            ]
+    toJSON (ReqDeleteKeys t ks) =
+        object
+            [ "method" .= ("delete_keys" :: T.Text)
+            , "table" .= t
+            , "keys" .= ks
+            ]
     toJSON (ReqReplaceAll t rs) =
         object
             [ "method" .= ("replace_all" :: T.Text)
@@ -184,10 +200,11 @@ instance ToJSON Request where
             , "rows" .= map rowToJSON rs
             ]
     toJSON ReqListTables = object ["method" .= ("list_tables" :: T.Text)]
-    toJSON (ReqLookupByKey t k) =
+    toJSON (ReqLookupByColumn t c k) =
         object
             [ "method" .= ("lookup_by_index" :: T.Text)
             , "table" .= t
+            , "column" .= c
             , "key" .= k
             ]
     toJSON (ReqDescribeTable t) =
@@ -203,17 +220,40 @@ instance ToJSON Request where
             ]
     toJSON (ReqDropTable t) =
         object ["method" .= ("drop_table" :: T.Text), "table" .= t]
+    toJSON (ReqCreateIndex t c) =
+        object
+            [ "method" .= ("create_index" :: T.Text)
+            , "table" .= t
+            , "column" .= c
+            ]
+    toJSON (ReqDropIndex t c) =
+        object
+            [ "method" .= ("drop_index" :: T.Text)
+            , "table" .= t
+            , "column" .= c
+            ]
     toJSON ReqListCatalog = object ["method" .= ("list_catalog" :: T.Text)]
 
+-- | 一张表的线上信息：列 + 行数 + 索引 + 列统计
+data TableInfo = TableInfo
+    { tiTable :: String
+    , tiColumns :: [SchemaColumn]
+    , tiRows :: Int
+    , tiIndexes :: [String]
+    , tiStats :: [(String, Int, Bool)]
+    }
+    deriving (Show, Eq)
+
 -- | 响应类型
 data Response
     = RespPong
     | RespRows [Row]
     | RespTables [String]
-    | RespSchema [SchemaColumn] Int
+    | RespSchema TableInfo
+    | RespNoIndex
     | RespOk
     | RespError String
-    | RespCatalog [(String, [SchemaColumn], Int)]
+    | RespCatalog [TableInfo]
 
 -- | 响应解码
 instance FromJSON Response where
@@ -222,25 +262,35 @@ instance FromJSON Response where
         case status :: T.Text of
             "pong" -> pure RespPong
             "ok" -> pure RespOk
+            "no_index" -> pure RespNoIndex
             "rows" -> RespRows <$> (o .: "rows" >>= mapM rowFromJSON)
             "tables" -> RespTables <$> o .: "tables"
             "error" -> RespError <$> o .: "message"
-            "schema" -> do
-                cols <- o .: "columns"
-                cnt <- o .: "row_count"
-                pure (RespSchema cols cnt)
+            "schema" -> RespSchema <$> parseTable (A.Object o)
             "catalog" -> do
-                xs <- o .: "schemas"
-                parsed <- mapM parseTableSchema xs
-                pure (RespCatalog parsed)
+                xs <- o .: "schemas" :: Parser [A.Value]
+                RespCatalog <$> mapM parseTable xs
             other -> fail ("unknown status: " ++ T.unpack other)
       where
-        -- \| 解析一条 list_catalog 记录。
-        parseTableSchema = withObject "TableSchema" $ \o -> do
+        -- \| 解一张表的 schema（新字段都给了默认值，老响应也能解）
+        parseTable :: A.Value -> Parser TableInfo
+        parseTable = withObject "TableInfo" $ \o -> do
             t <- o .: "table"
             cols <- o .: "columns"
             cnt <- o .: "row_count"
-            pure (t, cols, cnt)
+            idx <- o .:? "indexes" .!= []
+            sts <- o .:? "stats" .!= []
+            idxCols <- mapM (\v -> withObject "IndexWire" (.: "column") v) (idx :: [A.Value])
+            stats <- mapM parseStat (sts :: [A.Value])
+            pure (TableInfo t cols cnt idxCols stats)
+
+        -- \| 解一条列统计
+        parseStat :: A.Value -> Parser (String, Int, Bool)
+        parseStat = withObject "ColumnStat" $ \o -> do
+            name <- o .: "name"
+            distinct <- o .: "distinct"
+            capped <- o .:? "capped" .!= False
+            pure (name, distinct, capped)
 
 -- | 值编码成 JSON
 valueToJSON :: Value -> A.Value
@@ -275,87 +325,88 @@ rowFromJSON _ = fail "row must be a JSON object"
 
 -- * 内部封装
 
+-- | 发一条请求，把响应翻成 Either。
+--
+-- 每个操作的区别只有两处：发什么请求、认哪种响应。所以固定套路收在这里：
+-- 对面报错 → `Left`；认得这种响应 → `Right`；其余一律算协议错（比如对面版本对不上）。
+ask :: String -> Request -> (Response -> Maybe a) -> IO (Either String a)
+ask what req recognize = do
+    resp <- sendRequest req
+    pure $ case resp of
+        RespError e -> Left e
+        other -> case recognize other of
+            Just a -> Right a
+            Nothing -> Left ("unexpected response to " ++ what)
+
+-- | 只认"成了"（多数写操作都这样）
+okOnly :: Response -> Maybe ()
+okOnly RespOk = Just ()
+okOnly _ = Nothing
+
 -- | 发 Scan
 doScan :: String -> IO (Either String [Row])
-doScan t = do
-    resp <- sendRequest (ReqScan t)
-    pure $ case resp of
-        RespRows rows -> Right rows
-        RespError e -> Left e
-        _ -> Left "unexpected response to scan"
+doScan t = ask "scan" (ReqScan t) $ \resp -> case resp of
+    RespRows rows -> Just rows
+    _ -> Nothing
 
--- | 发 Insert，可带索引键。
-doInsertWith :: String -> Row -> Maybe Int -> IO (Either String ())
-doInsertWith t r mk = do
-    resp <- sendRequest (ReqInsert t r mk)
-    pure $ case resp of
-        RespOk -> Right ()
-        RespError e -> Left e
-        _ -> Left "unexpected response to insert"
+-- | 发 Insert（索引由存储层自己维护，这里不传 key）
+doInsert :: String -> Row -> IO (Either String ())
+doInsert t r = ask "insert" (ReqInsert t r) okOnly
+
+-- | 发 InsertBatch：一批行一次请求
+doInsertMany :: String -> [Row] -> IO (Either String ())
+doInsertMany t rs = ask "insert_batch" (ReqInsertBatch t rs) okOnly
+
+-- | 发 DeleteKeys
+doDeleteKeys :: String -> [Int] -> IO (Either String ())
+doDeleteKeys t ks = ask "delete_keys" (ReqDeleteKeys t ks) okOnly
 
 -- | 发 ReplaceAll
 doReplaceAll :: String -> [Row] -> IO (Either String ())
-doReplaceAll t rs = do
-    resp <- sendRequest (ReqReplaceAll t rs)
-    pure $ case resp of
-        RespOk -> Right ()
-        RespError e -> Left e
-        _ -> Left "unexpected response to replace_all"
+doReplaceAll t rs = ask "replace_all" (ReqReplaceAll t rs) okOnly
 
 -- | 发 ListTables
 doListTables :: IO (Either String [String])
-doListTables = do
-    resp <- sendRequest ReqListTables
-    pure $ case resp of
-        RespTables ts -> Right ts
-        RespError e -> Left e
-        _ -> Left "unexpected response to list_tables"
+doListTables = ask "list_tables" ReqListTables $ \resp -> case resp of
+    RespTables ts -> Just ts
+    _ -> Nothing
 
--- | 一次拿全库 schema（表名 + 列 + 行数）。
-doListCatalog :: IO (Either String [(String, [SchemaColumn], Int)])
-doListCatalog = do
-    resp <- sendRequest ReqListCatalog
-    pure $ case resp of
-        RespCatalog xs -> Right xs
-        RespError e -> Left e
-        _ -> Left "unexpected response to list_catalog"
+-- | 一次拿全库 schema（表名 + 列 + 行数 + 索引 + 统计）。
+doListCatalog :: IO (Either String [TableInfo])
+doListCatalog = ask "list_catalog" ReqListCatalog $ \resp -> case resp of
+    RespCatalog xs -> Just xs
+    _ -> Nothing
 
--- | 发 LookupByIndex
-doLookupByKey :: String -> Int -> IO (Either String (Maybe Row))
-doLookupByKey t k = do
-    resp <- sendRequest (ReqLookupByKey t k)
-    pure $ case resp of
-        RespRows [] -> Right Nothing
-        RespRows (r : _) -> Right (Just r)
-        RespError e -> Left e
-        _ -> Left "unexpected response to lookup_by_index"
+-- | 按某一列的索引取一行。
+-- 返回 `NoIndex` 表示"这个列上没有索引"，上层据此退回全表扫描。
+doLookupByColumn :: String -> String -> Int -> IO (Either String IndexResult)
+doLookupByColumn t c k = ask "lookup_by_index" (ReqLookupByColumn t c k) $ \resp -> case resp of
+    RespRows [] -> Just (IndexRow Nothing)
+    RespRows (r : _) -> Just (IndexRow (Just r))
+    RespNoIndex -> Just NoIndex
+    _ -> Nothing
 
 -- | 发 DescribeTable
-doDescribeTable :: String -> IO (Either String ([SchemaColumn], Int))
-doDescribeTable t = do
-    resp <- sendRequest (ReqDescribeTable t)
-    pure $ case resp of
-        RespSchema cols n -> Right (cols, n)
-        RespError e -> Left e
-        _ -> Left "unexpected response to describe_table"
+doDescribeTable :: String -> IO (Either String TableInfo)
+doDescribeTable t = ask "describe_table" (ReqDescribeTable t) $ \resp -> case resp of
+    RespSchema info -> Just info
+    _ -> Nothing
+
+-- | 给某一列建索引
+doCreateIndex :: String -> String -> IO (Either String ())
+doCreateIndex t c = ask "create_index" (ReqCreateIndex t c) okOnly
+
+-- | 去掉某一列的索引
+doDropIndex :: String -> String -> IO (Either String ())
+doDropIndex t c = ask "drop_index" (ReqDropIndex t c) okOnly
 
 -- | 发 CreateTable
 doCreateTable :: String -> [SchemaColumn] -> IO (Either String ())
-doCreateTable t cols = do
-    resp <- sendRequest (ReqCreateTable t cols)
-    pure $ case resp of
-        RespOk -> Right ()
-        RespError e -> Left e
-        _ -> Left "unexpected response to create_table"
+doCreateTable t cols = ask "create_table" (ReqCreateTable t cols) okOnly
 
 -- | 发 DropTable
 doDropTable :: String -> IO (Either String ())
-doDropTable t = do
-    resp <- sendRequest (ReqDropTable t)
-    pure $ case resp of
-        RespOk -> Right ()
-        RespError e -> Left e
-        _ -> Left "unexpected response to drop_table"
+doDropTable t = ask "drop_table" (ReqDropTable t) okOnly
 
 -- * 表结构
 
@@ -375,14 +426,20 @@ instance MonadStorage IPCStorage where
     -- \| 发 Scan
     scan t = IPCStorage (doScan t)
 
-    -- \| 发 Insert
-    insert t r mk = IPCStorage (doInsertWith t r mk)
+    -- \| 发 Insert（索引由存储层自己维护）
+    insert t r = IPCStorage (doInsert t r)
+
+    -- \| 一批行一次请求：N 行只落一次盘
+    insertMany t rs = IPCStorage (doInsertMany t rs)
+
+    -- \| 按 id 批量删行
+    deleteKeys t ks = IPCStorage (doDeleteKeys t ks)
 
     -- \| 发 ReplaceAll
     replaceAll t rs = IPCStorage (doReplaceAll t rs)
 
-    -- \| 发 LookupByIndex
-    lookupByKey t k = IPCStorage (doLookupByKey t k)
+    -- \| 按某一列的索引取一行（没有索引就回 NoIndex）
+    lookupByColumn t c k = IPCStorage (doLookupByColumn t c k)
 
     -- \| 发 CreateTable
     createTable name cols = IPCStorage (doCreateTable name (map toWire cols))
@@ -395,6 +452,12 @@ instance MonadStorage IPCStorage where
     -- \| 发 DropTable
     dropTable name = IPCStorage (doDropTable name)
 
+    -- \| 建索引
+    createIndex t c = IPCStorage (doCreateIndex t c)
+
+    -- \| 删索引
+    dropIndex t c = IPCStorage (doDropIndex t c)
+
     -- \| 列表 + 逐表扫描拼库
     snapshot = IPCStorage $ do
         result <- doListCatalog
@@ -403,6 +466,19 @@ instance MonadStorage IPCStorage where
             Right xs -> mapM loadEntry xs
       where
         -- \| 加载一张表（schema 来自 catalog，行来自 scan）
-        loadEntry (t, cols, _n) = do
-            rows <- doScan t
-            pure (t, Table t (schemaToColumns cols) (either (const []) id rows))
+        loadEntry info = do
+            rows <- doScan (tiTable info)
+            pure
+                ( tiTable info
+                , Table (tiTable info) (schemaToColumns (tiColumns info)) (either (const []) id rows)
+                )
+
+    -- \| 只问数据字典要结构，一行数据都不拉过来
+    schema = IPCStorage $ do
+        result <- doListCatalog
+        pure $ case result of
+            Left _ -> []
+            Right xs ->
+                [ (tiTable i, Table (tiTable i) (schemaToColumns (tiColumns i)) [])
+                | i <- xs
+                ]
diff --git a/chusql-engine/src/ChuSQL/Storage/Memory.hs b/chusql-engine/src/ChuSQL/Storage/Memory.hs
index 41f1bf1..ca838ee 100644
--- a/chusql-engine/src/ChuSQL/Storage/Memory.hs
+++ b/chusql-engine/src/ChuSQL/Storage/Memory.hs
@@ -2,9 +2,11 @@ module ChuSQL.Storage.Memory (MemoryStorage (runMemoryStorage)) where
 
 import ChuSQL.Model
 import ChuSQL.Storage
-import Data.List (find)
 
 -- 内存实现：状态是 Database，错误通道是 Either String。
+--
+-- 它只实现"必须有"的那几个：批量插入、行级删除、索引、统计全走类的默认实现
+-- （内存里数据本来就在手上，扫一遍就是最快的做法）。
 
 -- * 实例
 
@@ -39,7 +41,7 @@ instance MonadStorage MemoryStorage where
         Right (Right (tableRows tbl), db)
 
     -- \| 追加一行
-    insert t r _ = MemoryStorage $ \db -> do
+    insert t r = MemoryStorage $ \db -> do
         tbl <- lookupTable db t
         Right (Right (), replaceTable t tbl{tableRows = tableRows tbl ++ [r]} db)
 
@@ -48,11 +50,6 @@ instance MonadStorage MemoryStorage where
         tbl <- lookupTable db t
         Right (Right (), replaceTable t tbl{tableRows = rows} db)
 
-    -- \| 按主键找第一行
-    lookupByKey t k = MemoryStorage $ \db -> do
-        tbl <- lookupTable db t
-        Right (Right (findRow tbl k), db)
-
     -- \| 建空表；已存在报错
     createTable name cols = MemoryStorage $ \db ->
         if any ((== name) . fst) db
@@ -70,14 +67,8 @@ instance MonadStorage MemoryStorage where
 
 -- * 工具
 
--- | 按 id 列找一行
-findRow :: Table -> Int -> Maybe Row
-findRow tbl k = find matches (tableRows tbl)
-  where
-    -- \| 这行的 id 是否等于 k
-    matches r = lookup "id" r == Just (VInt k)
-
 -- | 用给定表替换同名表
 replaceTable :: String -> Table -> Database -> Database
 replaceTable name table =
     map (\(n, t) -> if n == name then (n, table) else (n, t))
+
diff --git a/chusql-engine/src/ChuSQL/Syntax/AST.hs b/chusql-engine/src/ChuSQL/Syntax/AST.hs
index 9398e35..a5c02c0 100644
--- a/chusql-engine/src/ChuSQL/Syntax/AST.hs
+++ b/chusql-engine/src/ChuSQL/Syntax/AST.hs
@@ -6,7 +6,7 @@ import ChuSQL.Model (Column (..))
 
 -- * 语句
 
--- | 一条语句：查 / 加 / 删 / 改 / 建表 / 删表
+-- | 一条语句：查 / 加 / 删 / 改 / 建表 / 删表 / 建索引 / 删索引
 data Statement
     = Select
         { selectCols :: [String]
@@ -15,11 +15,15 @@ data Statement
         , selectOrderBy :: [(String, SortDir)]
         , selectLimit :: Maybe Int
         }
-    | Insert String [String] [Expr]
+    | -- \| 表、列、若干行（`VALUES (...), (...)` 可以一次给多行）
+      Insert String [String] [[Expr]]
     | Delete String (Maybe Expr)
     | Update String [(String, Expr)] (Maybe Expr)
     | CreateTable String [(String, Column)]
     | DropTable String
+    | -- \| 给某一列建索引（列名即索引名）
+      CreateIndex String String
+    | DropIndex String String
     deriving (Show, Eq)
 
 -- | 数据来源：单表，或两表拼接
diff --git a/chusql-engine/src/ChuSQL/Syntax/Parser.hs b/chusql-engine/src/ChuSQL/Syntax/Parser.hs
index 4cbd4f5..34102f0 100644
--- a/chusql-engine/src/ChuSQL/Syntax/Parser.hs
+++ b/chusql-engine/src/ChuSQL/Syntax/Parser.hs
@@ -171,6 +171,8 @@ reservedWords =
     , "set"
     , "create"
     , "table"
+    , "index"
+    , "drop"
     ]
 
 {- | 表别名。别名不能是保留字：否则 @FROM users WHERE age > 18@ 会把 @WHERE@
@@ -232,6 +234,26 @@ dropTableStatement = do
     name <- identifier
     return (DropTable name)
 
+-- | 读 CREATE INDEX（列名即索引名：一列最多一个索引）
+createIndexStatement :: Parser Statement
+createIndexStatement = do
+    keyword "create"
+    keyword "index"
+    keyword "on"
+    tbl <- identifier
+    col <- between (symbol "(") (symbol ")") identifier
+    return (CreateIndex tbl col)
+
+-- | 读 DROP INDEX
+dropIndexStatement :: Parser Statement
+dropIndexStatement = do
+    keyword "drop"
+    keyword "index"
+    keyword "on"
+    tbl <- identifier
+    col <- between (symbol "(") (symbol ")") identifier
+    return (DropIndex tbl col)
+
 -- | 建表时的一列
 columnDef :: Parser (String, Column)
 columnDef = do
@@ -270,7 +292,7 @@ selectStatement = do
             , selectLimit = mLimit
             }
 
--- | 读 INSERT
+-- | 读 INSERT：`VALUES (...)` 后面可以跟多个括号，一次插多行
 insertStatement :: Parser Statement
 insertStatement = do
     keyword "INSERT"
@@ -282,12 +304,12 @@ insertStatement = do
             (symbol ")")
             (sepBy1 identifier (symbol ","))
     keyword "VALUES"
-    vals <-
-        between
-            (symbol "(")
-            (symbol ")")
-            (sepBy1 atom (symbol ","))
-    return (Insert tbl cols vals)
+    rows <- sepBy1 valueRow (symbol ",")
+    return (Insert tbl cols rows)
+
+-- | 一行值：一对括号里的若干字面量
+valueRow :: Parser [Expr]
+valueRow = between (symbol "(") (symbol ")") (sepBy1 atom (symbol ","))
 
 -- | 读 DELETE
 deleteStatement :: Parser Statement
@@ -316,11 +338,16 @@ parseStatement input =
         Left err -> Left (errorBundlePretty err)
         Right q -> Right q
   where
-    -- \| 依次尝试各种语句
+    -- \| 依次尝试各种语句。
+    -- `CREATE` / `DROP` 后面跟的词决定是哪条语句，而 `keyword` 的 `try` 只能回溯到
+    -- "这个词之前"——`CREATE` 一旦被吃掉就没得退了。所以带 `INDEX` 的那两个各自
+    -- 用 `try` 包住并排在前面：`CREATE INDEX ...` 先试，退回来再试 `CREATE TABLE ...`。
     statementP =
         selectStatement
             <|> insertStatement
             <|> deleteStatement
             <|> updateStatement
-            <|> createTableStatement
+            <|> try createIndexStatement
+            <|> try createTableStatement
+            <|> try dropIndexStatement
             <|> dropTableStatement
diff --git a/chusql-engine/test/Spec.hs b/chusql-engine/test/Spec.hs
index b899f85..efe726f 100644
--- a/chusql-engine/test/Spec.hs
+++ b/chusql-engine/test/Spec.hs
@@ -6,7 +6,7 @@ import ChuSQL.Algebra.Optimize (optimize, pushProject)
 import ChuSQL.Algebra.Planner (translate)
 import ChuSQL.Engine
 import ChuSQL.Model
-import ChuSQL.Storage (MonadStorage (..))
+import ChuSQL.Storage (IndexResult (..), MonadStorage (..))
 import ChuSQL.Storage.IPC (IPCStorage (runIPCStorage), Request (ReqPing), Response (RespPong), doListTables, sendRequest)
 import ChuSQL.Syntax.AST
 import ChuSQL.Syntax.Parser
@@ -299,18 +299,18 @@ main = hspec $ do
     describe "ChuSQL.Engine (INSERT)" $ do
         it "parses a simple INSERT" $ do
             parseStatement "INSERT INTO users (name, age) VALUES ('Dave', 22)"
-                `shouldBe` Right (Insert "users" ["name", "age"] [LitStr "Dave", LitInt 22])
+                `shouldBe` Right (Insert "users" ["name", "age"] [[LitStr "Dave", LitInt 22]])
 
         it "parses INSERT with a single column" $ do
             parseStatement "INSERT INTO users (name) VALUES ('Eve')"
-                `shouldBe` Right (Insert "users" ["name"] [LitStr "Eve"])
+                `shouldBe` Right (Insert "users" ["name"] [[LitStr "Eve"]])
 
         it "parses INSERT case-insensitively" $ do
             parseStatement "insert into users (name, age) values ('Dave', 22)"
-                `shouldBe` Right (Insert "users" ["name", "age"] [LitStr "Dave", LitInt 22])
+                `shouldBe` Right (Insert "users" ["name", "age"] [[LitStr "Dave", LitInt 22]])
 
         it "executes INSERT and adds a row at the end" $ do
-            case runStatement testDB (Insert "users" ["name", "age"] [LitStr "Dave", LitInt 22]) of
+            case runStatement testDB (Insert "users" ["name", "age"] [[LitStr "Dave", LitInt 22]]) of
                 Left err -> expectationFailure err
                 Right (db', _) -> do
                     rowsOf (runStatement db' (makeSelect ["name", "age"] "users" Nothing))
@@ -322,7 +322,7 @@ main = hspec $ do
                             ]
 
         it "does not modify the original database" $ do
-            case runStatement testDB (Insert "users" ["name", "age"] [LitStr "Dave", LitInt 22]) of
+            case runStatement testDB (Insert "users" ["name", "age"] [[LitStr "Dave", LitInt 22]]) of
                 Left err -> expectationFailure err
                 Right (_, _) -> do
                     rowsOf (runStatement testDB (makeSelect ["name"] "users" Nothing))
@@ -331,15 +331,15 @@ main = hspec $ do
                             Left _ -> False
 
         it "returns Left when column count does not match value count" $ do
-            runStatement testDB (Insert "users" ["name", "age"] [LitStr "Dave"])
+            runStatement testDB (Insert "users" ["name", "age"] [[LitStr "Dave"]])
                 `shouldSatisfy` isLeft
 
         it "returns Left for an unknown table" $ do
-            runStatement testDB (Insert "nonexistent" ["name"] [LitStr "X"])
+            runStatement testDB (Insert "nonexistent" ["name"] [[LitStr "X"]])
                 `shouldSatisfy` isLeft
 
         it "returns Left when a value has the wrong type for comparison" $ do
-            runStatement testDB (Insert "users" ["name"] [Col "other"])
+            runStatement testDB (Insert "users" ["name"] [[Col "other"]])
                 `shouldSatisfy` isLeft
         it "writes id column to index and queries it back" $ do
             case parseStatement "INSERT INTO users (id, name, age) VALUES (42, 'Zoe', 20)" >>= runStatement testDB of
@@ -347,6 +347,49 @@ main = hspec $ do
                 Right (db', _) -> do
                     rowsOf (parseStatement "SELECT name FROM users WHERE id = 42" >>= runStatement db')
                         `shouldBe` Right [[("name", VStr "Zoe")]]
+
+        it "parses multi-row INSERT into one statement" $ do
+            parseStatement "INSERT INTO users (id, name) VALUES (10, 'A'), (11, 'B'), (12, 'C')"
+                `shouldBe` Right
+                    ( Insert
+                        "users"
+                        ["id", "name"]
+                        [ [LitInt 10, LitStr "A"]
+                        , [LitInt 11, LitStr "B"]
+                        , [LitInt 12, LitStr "C"]
+                        ]
+                    )
+
+        it "inserts all rows of a multi-row INSERT" $ do
+            case parseStatement "INSERT INTO users (id, name, age) VALUES (7, 'A', 1), (8, 'B', 2)" >>= runStatement testDB of
+                Left err -> expectationFailure err
+                Right (db', _) -> do
+                    rowsOf (parseStatement "SELECT name FROM users WHERE age < 3" >>= runStatement db')
+                        `shouldBe` Right [[("name", VStr "A")], [("name", VStr "B")]]
+                    -- 多行里只要有一行列数不对，整条都要拒绝
+                    runStatement testDB (Insert "users" ["id", "name"] [[LitInt 1, LitStr "A"], [LitInt 2]])
+                        `shouldSatisfy` isLeft
+
+    describe "ChuSQL.Engine (INDEX)" $ do
+        it "parses CREATE INDEX and DROP INDEX" $ do
+            parseStatement "CREATE INDEX ON users (age)"
+                `shouldBe` Right (CreateIndex "users" "age")
+            parseStatement "DROP INDEX ON users (age)"
+                `shouldBe` Right (DropIndex "users" "age")
+
+        it "rejects an index on an unknown column" $ do
+            (parseStatement "CREATE INDEX ON users (nope)" >>= runStatement testDB)
+                `shouldSatisfy` isLeft
+
+        it "rejects an index on an unknown table" $ do
+            (parseStatement "CREATE INDEX ON nope (age)" >>= runStatement testDB)
+                `shouldSatisfy` isLeft
+
+        it "accepts index DDL in the memory storage (no-op there)" $ do
+            rowsOf (parseStatement "CREATE INDEX ON users (age)" >>= runStatement testDB)
+                `shouldBe` Right []
+            rowsOf (parseStatement "DROP INDEX ON users (age)" >>= runStatement testDB)
+                `shouldBe` Right []
     describe "ChuSQL.Engine (DELETE)" $ do
         it "parses DELETE with WHERE" $ do
             parseStatement "DELETE FROM users WHERE age < 18"
@@ -961,10 +1004,27 @@ main = hspec $ do
             sameResultAsUnoptimized "SELECT u.name FROM users u JOIN orders o ON u.id = o.user_id ORDER BY o.product DESC LIMIT 2"
         it "rewrites Filter id = k into Lookup" $ do
             fmap planRoot (optimizedPlan "SELECT name FROM users WHERE id = 2")
-                `shouldBe` Right (Lookup "users" 2)
+                `shouldBe` Right (Lookup Nothing "users" "id" 2)
         it "keeps Lookup result identical to unoptimized" $ do
             sameResultAsUnoptimized "SELECT name FROM users WHERE id = 2"
 
+        it "rewrites an equality on any column into Lookup" $ do
+            -- 能不能真走索引由存储层回答；优化器只负责说"这里可以点查"
+            fmap planRoot (optimizedPlan "SELECT name FROM users WHERE age = 25")
+                `shouldBe` Right (Lookup Nothing "users" "age" 25)
+
+        it "keeps a point lookup on a non-indexed column identical to unoptimized" $ do
+            -- 内存实现没有索引，这条会走"退回扫描"的分支
+            sameResultAsUnoptimized "SELECT name FROM users WHERE age = 25"
+
+        it "keeps an aliased point lookup identical to unoptimized" $ do
+            -- 别名要留住：回来的一行必须和 Scan 别名 表 长得一样，不然投影取不到列
+            sameResultAsUnoptimized "SELECT u.name FROM users u WHERE u.id = 1"
+
+        it "returns the row for an aliased point lookup" $ do
+            rowsOf (parseStatement "SELECT u.name FROM users u WHERE u.id = 1" >>= runStatement testDB)
+                `shouldBe` Right [[("u.name", VStr "Alice")]]
+
     describe "ChuSQL.Semantic" $ do
         it "rejects an unknown column in WHERE" $ do
             (parseStatement "SELECT name FROM users WHERE nope > 18" >>= runStatement testDB)
@@ -1108,7 +1168,7 @@ main = hspec $ do
         it "scan returns rows with all three value types after insert" $ do
             withTestServer $ \srv -> withServerEnv srv $ do
                 let row = [("id", VInt 7), ("name", VStr "Alice"), ("flag", VBool True)]
-                runIPCStorage (insert "users" row (Just 7)) `shouldReturn` Right ()
+                runIPCStorage (insert "users" row) `shouldReturn` Right ()
                 rows <- runIPCStorage (scan "users")
                 (map sortRow <$> rows) `shouldBe` Right [sortRow row]
 
@@ -1119,7 +1179,7 @@ main = hspec $ do
 
         it "scan returns all 20 inserted rows in order" $ do
             withTestServer $ \srv -> withServerEnv srv $ do
-                mapM_ (\i -> runIPCStorage (insert "many" [("id", VInt i)] (Just i))) [1 .. 20 :: Int]
+                mapM_ (\i -> runIPCStorage (insert "many" [("id", VInt i)])) [1 .. 20 :: Int]
                 rows <- runIPCStorage (scan "many")
                 fmap length rows `shouldBe` Right 20
                 fmap (sortOn show . map (lookup "id")) rows
@@ -1127,35 +1187,35 @@ main = hspec $ do
 
         it "replaceAll leaves only the new rows" $ do
             withTestServer $ \srv -> withServerEnv srv $ do
-                runIPCStorage (insert "t" [("id", VInt 1)] (Just 1)) `shouldReturn` Right ()
+                runIPCStorage (insert "t" [("id", VInt 1)]) `shouldReturn` Right ()
                 runIPCStorage (replaceAll "t" [[("id", VInt 9)], [("id", VInt 8)]]) `shouldReturn` Right ()
                 rows <- runIPCStorage (scan "t")
                 fmap (sortOn show . map (lookup "id")) rows
                     `shouldBe` Right (sortOn show [Just (VInt 9), Just (VInt 8)])
 
-        it "lookupByKey finds a row inserted with an id over the pipe" $ do
+        it "lookupByColumn finds a row inserted with an id over the pipe" $ do
             withTestServer $ \srv -> withServerEnv srv $ do
                 let row = [("id", VInt 7), ("name", VStr "Zoe")]
-                runIPCStorage (insert "keyed" row (Just 7)) `shouldReturn` Right ()
-                found <- runIPCStorage (lookupByKey "keyed" 7)
-                fmap (fmap sortRow) found `shouldBe` Right (Just (sortRow row))
-                missing <- runIPCStorage (lookupByKey "keyed" 8)
-                missing `shouldBe` Right Nothing
+                runIPCStorage (insert "keyed" row) `shouldReturn` Right ()
+                found <- runIPCStorage (lookupByColumn "keyed" "id" 7)
+                fmap sortRow (indexRow found) `shouldBe` Just (sortRow row)
+                missing <- runIPCStorage (lookupByColumn "keyed" "id" 8)
+                missing `shouldBe` Right (IndexRow Nothing)
 
         it "replaceAll rebuilds the index over the pipe" $ do
             withTestServer $ \srv -> withServerEnv srv $ do
-                runIPCStorage (insert "rb" [("id", VInt 1)] (Just 1)) `shouldReturn` Right ()
+                runIPCStorage (insert "rb" [("id", VInt 1)]) `shouldReturn` Right ()
                 runIPCStorage (replaceAll "rb" [[("id", VInt 9), ("name", VStr "Zoe")]]) `shouldReturn` Right ()
-                old <- runIPCStorage (lookupByKey "rb" 1)
-                old `shouldBe` Right Nothing
-                new <- runIPCStorage (lookupByKey "rb" 9)
-                fmap (fmap sortRow) new
-                    `shouldBe` Right (Just (sortRow [("id", VInt 9), ("name", VStr "Zoe")]))
+                old <- runIPCStorage (lookupByColumn "rb" "id" 1)
+                old `shouldBe` Right (IndexRow Nothing)
+                new <- runIPCStorage (lookupByColumn "rb" "id" 9)
+                fmap sortRow (indexRow new)
+                    `shouldBe` Just (sortRow [("id", VInt 9), ("name", VStr "Zoe")])
 
         it "snapshot lists tables and scans each one to build the database" $ do
             withTestServer $ \srv -> withServerEnv srv $ do
-                runIPCStorage (insert "a" [("id", VInt 1)] (Just 1)) `shouldReturn` Right ()
-                runIPCStorage (insert "b" [("id", VInt 2)] (Just 2)) `shouldReturn` Right ()
+                runIPCStorage (insert "a" [("id", VInt 1)]) `shouldReturn` Right ()
+                runIPCStorage (insert "b" [("id", VInt 2)]) `shouldReturn` Right ()
                 db <- runIPCStorage snapshot
                 map fst db `shouldBe` ["a", "b"]
                 map (length . tableRows . snd) db `shouldBe` [1, 1]
@@ -1163,8 +1223,8 @@ main = hspec $ do
 
         it "doListTables returns the tables that exist" $ do
             withTestServer $ \srv -> withServerEnv srv $ do
-                runIPCStorage (insert "t1" [("id", VInt 1)] (Just 1)) `shouldReturn` Right ()
-                runIPCStorage (insert "t2" [("id", VInt 2)] (Just 2)) `shouldReturn` Right ()
+                runIPCStorage (insert "t1" [("id", VInt 1)]) `shouldReturn` Right ()
+                runIPCStorage (insert "t2" [("id", VInt 2)]) `shouldReturn` Right ()
                 doListTables `shouldReturn` Right ["t1", "t2"]
 
         it "rows survive a restart on the same data directory" $ do
@@ -1174,7 +1234,7 @@ main = hspec $ do
                 Right bin -> do
                     srv1 <- startServer bin
                     let dir = dataDir srv1
-                    withServerEnv srv1 $ runIPCStorage (insert "persist" [("id", VInt 42)] (Just 42)) `shouldReturn` Right ()
+                    withServerEnv srv1 $ runIPCStorage (insert "persist" [("id", VInt 42)]) `shouldReturn` Right ()
                     stopServer srv1
                     srv2 <- startServerAt bin dir
                     rows <- withServerEnv srv2 $ runIPCStorage (scan "persist")
@@ -1196,7 +1256,7 @@ main = hspec $ do
                 _ <-
                     runIPCStorage
                         ( runStatementM
-                            (Insert "ipc_idx" ["id", "name"] [LitInt 42, LitStr "Zoe"])
+                            (Insert "ipc_idx" ["id", "name"] [[LitInt 42, LitStr "Zoe"]])
                         )
                 result <-
                     runIPCStorage
@@ -1211,6 +1271,76 @@ main = hspec $ do
                             )
                         )
                 result `shouldBe` Right [[("name", VStr "Zoe")]]
+
+        it "CREATE INDEX makes a query on that column use the index" $ do
+            withTestServer $ \srv -> withServerEnv srv $ do
+                _ <- runIPCStorage (runStatementM (CreateTable "ix_t" [("id", TInt), ("code", TInt)]))
+                _ <-
+                    runIPCStorage
+                        ( runStatementM
+                            (Insert "ix_t" ["id", "code"] [[LitInt 1, LitInt 500], [LitInt 2, LitInt 501]])
+                        )
+
+                -- 还没建索引：存储层明确回"我帮不上忙"，上层会退回扫描
+                withoutIndex <- runIPCStorage (lookupByColumn "ix_t" "code" 501)
+                withoutIndex `shouldBe` Right NoIndex
+                scanned <- runIPCStorage (runStatementM (makeSelect ["code"] "ix_t" (Just (Eq (Col "code") (LitInt 501)))))
+                scanned `shouldBe` Right [[("code", VInt 501)]]
+
+                -- 建索引之后就真的走索引了
+                created <- runIPCStorage (runStatementM (CreateIndex "ix_t" "code"))
+                created `shouldBe` Right []
+                withIndex <- runIPCStorage (lookupByColumn "ix_t" "code" 501)
+                fmap sortRow (indexRow withIndex)
+                    `shouldBe` Just (sortRow [("id", VInt 2), ("code", VInt 501)])
+                indexed <- runIPCStorage (runStatementM (makeSelect ["code"] "ix_t" (Just (Eq (Col "code") (LitInt 501)))))
+                indexed `shouldBe` Right [[("code", VInt 501)]]
+
+                -- 建完索引之后插入的行也要进索引
+                _ <- runIPCStorage (runStatementM (Insert "ix_t" ["id", "code"] [[LitInt 3, LitInt 502]]))
+                fresh <- runIPCStorage (lookupByColumn "ix_t" "code" 502)
+                fmap sortRow (indexRow fresh)
+                    `shouldBe` Just (sortRow [("id", VInt 3), ("code", VInt 502)])
+
+        it "CREATE INDEX over the pipe rejects a column with duplicates" $ do
+            withTestServer $ \srv -> withServerEnv srv $ do
+                _ <- runIPCStorage (runStatementM (CreateTable "dup_ix" [("id", TInt), ("age", TInt)]))
+                _ <-
+                    runIPCStorage
+                        ( runStatementM
+                            (Insert "dup_ix" ["id", "age"] [[LitInt 1, LitInt 30], [LitInt 2, LitInt 30]])
+                        )
+                res <- runIPCStorage (runStatementM (CreateIndex "dup_ix" "age"))
+                res `shouldSatisfy` isLeft
+
+        it "DELETE removes only the matching rows over the pipe" $ do
+            withTestServer $ \srv -> withServerEnv srv $ do
+                _ <- runIPCStorage (runStatementM (CreateTable "del_t" [("id", TInt), ("name", TStr)]))
+                _ <-
+                    runIPCStorage
+                        ( runStatementM
+                            ( Insert
+                                "del_t"
+                                ["id", "name"]
+                                [[LitInt 1, LitStr "A"], [LitInt 2, LitStr "B"], [LitInt 3, LitStr "C"]]
+                            )
+                        )
+                _ <- runIPCStorage (runStatementM (Delete "del_t" (Just (Eq (Col "id") (LitInt 2)))))
+                rows <- runIPCStorage (runStatementM (makeSelect ["name"] "del_t" Nothing))
+                rows `shouldBe` Right [[("name", VStr "A")], [("name", VStr "C")]]
+                gone <- runIPCStorage (lookupByColumn "del_t" "id" 2)
+                gone `shouldBe` Right (IndexRow Nothing)
+
+        it "multi-row INSERT goes over the pipe in one statement" $ do
+            withTestServer $ \srv -> withServerEnv srv $ do
+                _ <- runIPCStorage (runStatementM (CreateTable "many_t" [("id", TInt)]))
+                _ <-
+                    runIPCStorage
+                        ( runStatementM
+                            (Insert "many_t" ["id"] [[LitInt i] | i <- [1 .. 50]])
+                        )
+                rows <- runIPCStorage (runStatementM (makeSelect ["id"] "many_t" Nothing))
+                fmap length rows `shouldBe` Right 50
         it "parses CREATE TABLE with two columns" $ do
             parseStatement "CREATE TABLE users (id INT, name TEXT)"
                 `shouldBe` Right (CreateTable "users" [("id", TInt), ("name", TStr)])
@@ -1392,6 +1522,11 @@ withPipeName name act = do
 sortRow :: Row -> Row
 sortRow = sortOn fst
 
+-- | 从一次索引点查的结果里取出那一行（没索引、没查到都给 Nothing）
+indexRow :: Either String IndexResult -> Maybe Row
+indexRow (Right (IndexRow r)) = r
+indexRow _ = Nothing
+
 isLeft :: Either a b -> Bool
 isLeft (Left _) = True
 isLeft (Right _) = False
@@ -1428,7 +1563,7 @@ firstFilterCond (Join l r _) = case firstFilterCond l of
     Just p -> Just p
     Nothing -> firstFilterCond r
 firstFilterCond (Scan _ _) = Nothing
-firstFilterCond (Lookup _ _) = Nothing
+firstFilterCond (Lookup _ _ _ _) = Nothing
 
 anyFilter :: RelOp -> Bool
 anyFilter (Filter _ _) = True
@@ -1437,7 +1572,7 @@ anyFilter (Sort _ x) = anyFilter x
 anyFilter (Limit _ x) = anyFilter x
 anyFilter (Join l r _) = anyFilter l || anyFilter r
 anyFilter (Scan _ _) = False
-anyFilter (Lookup _ _) = False
+anyFilter (Lookup _ _ _ _) = False
 
 stripProjects :: RelOp -> RelOp
 stripProjects (Project _ x) = stripProjects x
@@ -1446,7 +1581,7 @@ stripProjects (Sort spec x) = Sort spec (stripProjects x)
 stripProjects (Limit n x) = Limit n (stripProjects x)
 stripProjects (Join l r c) = Join (stripProjects l) (stripProjects r) c
 stripProjects (Scan a t) = Scan a t
-stripProjects (Lookup t k) = Lookup t k
+stripProjects (Lookup a t c k) = Lookup a t c k
 
 projectedPlan :: String -> Either String RelOp
 projectedPlan sql = do
diff --git a/chusql-storage/src/bin/server.rs b/chusql-storage/src/bin/server.rs
index 18c397b..ba7985b 100644
--- a/chusql-storage/src/bin/server.rs
+++ b/chusql-storage/src/bin/server.rs
@@ -9,26 +9,25 @@ use chusql_storage::catalog::Catalog;
 use chusql_storage::config::{self, Config, Loaded};
 use chusql_storage::heap::HeapTable;
 use chusql_storage::log;
-use chusql_storage::protocol::{Request, Response, SchemaColumn, TableSchemaWire};
+use chusql_storage::protocol::{
+    ColumnStatWire, IndexWire, Request, Response, SchemaColumn, TableSchemaWire,
+};
 use chusql_storage::wal::{Wal, WalOp};
 use chusql_storage::{log_debug, log_error, log_info, log_warn};
-use interprocess::local_socket::{
-    prelude::*,
-    GenericNamespaced,
-    ListenerOptions,
-};
+use interprocess::local_socket::{prelude::*, GenericNamespaced, ListenerOptions};
 use interprocess::TryClone;
 
 // 命名管道服务：按行读写 JSON，Windows 上映射成 \\.\pipe\<name>。
 // 启动时读配置并把每项来源打进日志；表句柄按名字缓存复用。
 
 // 服务器
-/// 服务器状态：配置 + 表句柄缓存 + 写锁
+/// 服务器状态：配置 + 表句柄缓存 + 写锁 + 数据字典
 struct Server {
     cfg: Config,
     tables: Mutex<HashMap<String, Arc<Mutex<HeapTable>>>>,
     write_lock: Mutex<()>,
     catalog: Mutex<Catalog>,
+    wal: Wal,
 }
 
 impl Server {
@@ -36,23 +35,34 @@ impl Server {
     fn new(cfg: Config) -> std::io::Result<Self> {
         std::fs::create_dir_all(&cfg.data_dir)?;
         let catalog = Catalog::load(cfg.data_dir.join("catalog.json"))?;
+        let wal = Wal::new(cfg.data_dir.join("wal.log"));
         Ok(Server {
             cfg,
             tables: Mutex::new(HashMap::new()),
             write_lock: Mutex::new(()),
             catalog: Mutex::new(catalog),
+            wal,
         })
     }
 
-// 路径
+    // 路径
     /// 表名 -> 数据文件
     fn table_path(&self, table: &str) -> PathBuf {
         self.cfg.data_dir.join(format!("{}.db", table))
     }
 
-    /// 表名 -> 索引文件
-    fn index_path(&self, table: &str) -> PathBuf {
-        self.cfg.data_dir.join(format!("{}.idx", table))
+    /// (表名, 列名) -> 索引文件。
+    ///
+    /// `id` 是内建索引，沿用老文件名 `表名.idx`（老数据目录不用迁移）；
+    /// 其余列是 `表名.列名.idx`。
+    fn index_path(&self, table: &str, column: &str) -> PathBuf {
+        if column == "id" {
+            self.cfg.data_dir.join(format!("{}.idx", table))
+        } else {
+            self.cfg
+                .data_dir
+                .join(format!("{}.{}.idx", table, column))
+        }
     }
 
     /// 数据字典文件
@@ -60,13 +70,7 @@ impl Server {
         self.cfg.data_dir.join("catalog.json")
     }
 
-    /// WAL 文件
-    fn wal_path(&self) -> PathBuf {
-        self.cfg.data_dir.join("wal.log")
-    }
-
-
-// 表句柄
+    // 表句柄
     /// 表文件存在且非空
     fn table_exists(&self, table: &str) -> bool {
         if self.tables.lock().unwrap().contains_key(table) {
@@ -82,16 +86,40 @@ impl Server {
             .unwrap_or(false)
     }
 
+    /// 一张表该开哪些索引：内建的 `id`，加上数据字典里记的那些
+    fn index_columns(&self, table: &str) -> Vec<String> {
+        let mut cols = vec!["id".to_string()];
+        let c = self.catalog.lock().unwrap();
+        if let Some(s) = c.describe(table) {
+            for i in &s.indexes {
+                if !cols.contains(&i.column) {
+                    cols.push(i.column.clone());
+                }
+            }
+        }
+        cols
+    }
+
     /// 拿表句柄（缓存复用）
     fn table_handle(&self, table: &str) -> std::io::Result<Arc<Mutex<HeapTable>>> {
+        if let Some(h) = self.tables.lock().unwrap().get(table) {
+            return Ok(h.clone());
+        }
+        // 先把索引清单取出来，再进 tables 锁（别套着锁去要 catalog）
+        let columns = self.index_columns(table);
+        let paths: Vec<(String, PathBuf)> = columns
+            .iter()
+            .map(|c| (c.clone(), self.index_path(table, c)))
+            .collect();
+
         let mut map = self.tables.lock().unwrap();
         if let Some(h) = map.get(table) {
             return Ok(h.clone());
         }
         std::fs::create_dir_all(&self.cfg.data_dir)?;
-        let t = HeapTable::open_indexed(
+        let t = HeapTable::open_with_indexes(
             self.table_path(table),
-            self.index_path(table),
+            &paths,
             self.cfg.page_size,
             self.cfg.btree_order,
             self.cfg.pool_size,
@@ -112,15 +140,6 @@ impl Server {
         f(&mut guard)
     }
 
-    /// 同上，但一定带索引
-    fn with_indexed_table<R>(
-        &self,
-        table: &str,
-        f: impl FnOnce(&mut HeapTable) -> std::io::Result<R>,
-    ) -> std::io::Result<R> {
-        self.with_table(table, f)
-    }
-
     /// 表不存在就报错
     fn with_existing_table<R>(
         &self,
@@ -138,32 +157,45 @@ impl Server {
         self.with_table(table, f)
     }
 
-// 写入路径
+    // 写入路径
     /// 把一条 WAL 操作落到磁盘
     fn apply_op(&self, op: &WalOp) -> std::io::Result<()> {
         match op {
-            WalOp::Insert { table, row, key } => {
-                match key {
-                    None => self.with_table(table, |t| t.insert(row))?,
-                    Some(k) => self.with_indexed_table(table, |t| t.insert_keyed(row, *k))?,
-                }
-                let row: chusql_storage::protocol::Row = row.clone().into_iter().collect();
+            WalOp::Insert { table, row } => {
+                self.with_table(table, |t| t.insert_row(row))?;
                 let mut c = self.catalog.lock().unwrap();
-                if c.record_insert(table, &row) {
+                if c.record_insert(table, row) {
                     c.save(self.catalog_path())?;
                 }
                 Ok(())
             }
-            WalOp::ReplaceAll { table, rows } => {
-                self.with_indexed_table(table, |t| t.replace_all(rows))?;
-                let rows: Vec<chusql_storage::protocol::Row> =
-                    rows.iter().map(|r| r.clone().into_iter().collect()).collect();
+            WalOp::InsertBatch { table, rows } => {
+                self.with_table(table, |t| t.insert_rows(rows))?;
                 let mut c = self.catalog.lock().unwrap();
-                if c.record_replace_all(table, &rows) {
+                let mut changed = false;
+                for r in rows {
+                    if c.record_insert(table, r) {
+                        changed = true;
+                    }
+                }
+                if changed {
                     c.save(self.catalog_path())?;
                 }
                 Ok(())
             }
+            WalOp::DeleteKeys { table, keys } => {
+                let deleted = self.with_table(table, |t| t.delete_by_keys(keys))?;
+                let mut c = self.catalog.lock().unwrap();
+                c.record_delete(table, &deleted);
+                Ok(())
+            }
+            WalOp::ReplaceAll { table, rows } => {
+                self.with_table(table, |t| t.replace_all(rows))?;
+                // 整表重写 = 统计与行数从头再数一遍
+                let mut c = self.catalog.lock().unwrap();
+                c.rebuild_stats(table, rows);
+                c.save(self.catalog_path())
+            }
         }
     }
 
@@ -171,9 +203,11 @@ impl Server {
     fn write_via_wal(&self, op: &WalOp) -> std::io::Result<()> {
         let _guard = self.write_lock.lock().unwrap();
         std::fs::create_dir_all(&self.cfg.data_dir)?;
-        let wal = Wal::new(self.wal_path());
+        let wal = &self.wal;
 
-        wal.clear()?;
+        // 只截断不落盘：上一条写操作最后已经把 WAL 刷成空的了，
+        // 这里的截断只是保证下面追加的是唯一一条，跟着的 append 会顺手把它落下去。
+        wal.truncate()?;
 
         wal.append(op)?;
 
@@ -185,30 +219,26 @@ impl Server {
             }
         }
 
+        // 这一步必须落盘：WAL 空 = 这条操作已经提交
         wal.clear()?;
         result
     }
 
     /// 把涉及的表写回磁盘
     fn flush_op_tables(&self, op: &WalOp) -> std::io::Result<()> {
-        match op {
-            WalOp::Insert { table, key, .. } => {
-                if key.is_some() {
-                    self.with_indexed_table(table, |t| t.flush())
-                } else {
-                    self.with_table(table, |t| t.flush())
-                }
-            }
-            WalOp::ReplaceAll { table, .. } => {
-                self.with_indexed_table(table, |t| t.flush())
-            }
-        }
+        let table = match op {
+            WalOp::Insert { table, .. }
+            | WalOp::InsertBatch { table, .. }
+            | WalOp::DeleteKeys { table, .. }
+            | WalOp::ReplaceAll { table, .. } => table,
+        };
+        self.with_table(table, |t| t.flush())
     }
 
     /// 启动时重放残留 WAL
     fn recover_wal(&self) -> std::io::Result<()> {
         std::fs::create_dir_all(&self.cfg.data_dir)?;
-        let wal = Wal::new(self.wal_path());
+        let wal = &self.wal;
         match wal.read()? {
             None => Ok(()),
             Some(op) => {
@@ -221,8 +251,103 @@ impl Server {
         }
     }
 
+    /// 启动时把列统计重数一遍。
+    ///
+    /// 统计是"每列见过哪些值"精确数出来的，只在内存里维护（随 catalog 落盘），
+    /// 所以重启之后要扫一遍表把它重建出来；否则统计会随重启慢慢失真。
+    fn rebuild_stats(&self) -> std::io::Result<()> {
+        let names: Vec<String> = self.catalog.lock().unwrap().table_names();
+        let mut touched = false;
+        for table in names {
+            if !self.table_path(&table).exists() {
+                continue;
+            }
+            let rows = self.with_table(&table, |t| t.scan())?;
+            let mut c = self.catalog.lock().unwrap();
+            c.rebuild_stats(&table, &rows);
+            touched = true;
+        }
+        if touched {
+            let c = self.catalog.lock().unwrap();
+            c.save(self.catalog_path())?;
+        }
+        Ok(())
+    }
 
-// 请求分发
+    // 索引维护
+    /// 给一列建索引
+    fn create_index(&self, table: &str, column: &str) -> std::io::Result<()> {
+        if column == "id" {
+            return Err(std::io::Error::new(
+                std::io::ErrorKind::AlreadyExists,
+                "id 是内建索引，不需要再建",
+            ));
+        }
+        {
+            let c = self.catalog.lock().unwrap();
+            let Some(schema) = c.describe(table) else {
+                return Err(std::io::Error::new(
+                    std::io::ErrorKind::NotFound,
+                    format!("unknown table: {}", table),
+                ));
+            };
+            if !schema.columns.iter().any(|c| c.name == column) {
+                return Err(std::io::Error::new(
+                    std::io::ErrorKind::NotFound,
+                    format!("unknown column: {}", column),
+                ));
+            }
+            if schema.indexes.iter().any(|i| i.column == column) {
+                return Err(std::io::Error::new(
+                    std::io::ErrorKind::AlreadyExists,
+                    format!("index on column \"{}\" already exists", column),
+                ));
+            }
+        }
+
+        let path = self.index_path(table, column);
+        let (page_size, order, pool) = (self.cfg.page_size, self.cfg.btree_order, self.cfg.pool_size);
+        self.with_table(table, |t| {
+            t.build_index(column, &path, page_size, order, pool)
+        })?;
+
+        let mut c = self.catalog.lock().unwrap();
+        c.add_index(table, column)?;
+        c.save(self.catalog_path())
+    }
+
+    /// 去掉一列的索引（连文件一起删）
+    fn drop_index(&self, table: &str, column: &str) -> std::io::Result<()> {
+        if column == "id" {
+            return Err(std::io::Error::new(
+                std::io::ErrorKind::InvalidInput,
+                "id 是内建索引，不能删",
+            ));
+        }
+        {
+            let c = self.catalog.lock().unwrap();
+            if c.describe(table).is_none() {
+                return Err(std::io::Error::new(
+                    std::io::ErrorKind::NotFound,
+                    format!("unknown table: {}", table),
+                ));
+            }
+        }
+        self.with_table(table, |t| {
+            t.detach_index(column);
+            Ok(())
+        })?;
+
+        let mut c = self.catalog.lock().unwrap();
+        c.remove_index(table, column)?;
+        c.save(self.catalog_path())?;
+        drop(c);
+
+        let _ = std::fs::remove_file(self.index_path(table, column));
+        Ok(())
+    }
+
+    // 请求分发
     /// 一条请求翻成一条响应
     fn handle_request(&self, req: Request) -> Response {
         match req {
@@ -247,10 +372,10 @@ impl Server {
                 }
             }
 
-            Request::Insert { table, row, key } => {
-                log_debug!(pipe, "insert table={} key={:?}", table, key);
+            Request::Insert { table, row } => {
+                log_debug!(pipe, "insert table={}", table);
                 let tname = table.clone();
-                let op = WalOp::Insert { table, row, key };
+                let op = WalOp::Insert { table, row };
                 match self.write_via_wal(&op) {
                     Ok(()) => Response::Ok,
                     Err(e) => {
@@ -262,9 +387,54 @@ impl Server {
                 }
             }
 
-            Request::LookupByIndex { table, key } => {
-                log_debug!(pipe, "lookup_by_index table={} key={}", table, key);
-                match self.with_indexed_table(&table, |t| t.get_by_key(key)) {
+            Request::InsertBatch { table, rows } => {
+                log_debug!(pipe, "insert_batch table={} rows={}", table, rows.len());
+                let tname = table.clone();
+                let op = WalOp::InsertBatch { table, rows };
+                match self.write_via_wal(&op) {
+                    Ok(()) => Response::Ok,
+                    Err(e) => {
+                        log_warn!(pipe, "insert_batch {}: {}", tname, e);
+                        Response::Error {
+                            message: format!("insert_batch {}: {}", tname, e),
+                        }
+                    }
+                }
+            }
+
+            Request::DeleteKeys { table, keys } => {
+                log_debug!(pipe, "delete_keys table={} keys={}", table, keys.len());
+                let tname = table.clone();
+                let op = WalOp::DeleteKeys { table, keys };
+                match self.write_via_wal(&op) {
+                    Ok(()) => Response::Ok,
+                    Err(e) => {
+                        log_warn!(pipe, "delete_keys {}: {}", tname, e);
+                        Response::Error {
+                            message: format!("delete_keys {}: {}", tname, e),
+                        }
+                    }
+                }
+            }
+
+            Request::LookupByIndex { table, column, key } => {
+                log_debug!(pipe, "lookup_by_index table={} column={} key={}", table, column, key);
+                let indexed =
+                    match self.with_existing_table(&table, |t| Ok(t.has_index(&column))) {
+                        Ok(v) => v,
+                        Err(e) => {
+                            log_warn!(pipe, "lookup_by_index {}: {}", table, e);
+                            return Response::Error {
+                                message: format!("lookup_by_index {}: {}", table, e),
+                            };
+                        }
+                    };
+                if !indexed {
+                    // 没有这个索引：告诉查询层"这条我帮不上忙"，让它退回全表扫描。
+                    // 回 NoIndex 而不是空结果，是因为"没有索引"和"没查到"必须分开。
+                    return Response::NoIndex;
+                }
+                match self.with_table(&table, |t| t.get_by_column_key(&column, key)) {
                     Ok(Some(row)) => Response::Rows { rows: vec![row] },
                     Ok(None) => Response::Rows { rows: vec![] },
                     Err(e) => {
@@ -314,6 +484,8 @@ impl Server {
                         table: name.to_string(),
                         columns: ts.columns.clone(),
                         row_count: ts.row_count,
+                        indexes: index_wires(ts),
+                        stats: stat_wires(ts),
                     })
                     .collect();
                 Response::Catalog { schemas }
@@ -322,9 +494,12 @@ impl Server {
             Request::DescribeTable { table } => {
                 log_debug!(pipe, "describe_table table={}", table);
                 match self.describe_table(&table) {
-                    Ok((cols, count)) => Response::Schema {
+                    Ok((cols, count, indexes, stats)) => Response::Schema {
+                        table,
                         columns: cols,
                         row_count: count,
+                        indexes,
+                        stats,
                     },
                     Err(e) => {
                         log_warn!(pipe, "describe_table {}: {}", table, e);
@@ -370,8 +545,12 @@ impl Server {
             Request::DropTable { table } => {
                 log_debug!(pipe, "drop_table table={}", table);
 
-                {
+                let dropped_indexes: Vec<String> = {
                     let mut c = self.catalog.lock().unwrap();
+                    let idx = c
+                        .describe(&table)
+                        .map(|s| s.indexes.iter().map(|i| i.column.clone()).collect())
+                        .unwrap_or_default();
                     if let Err(e) = c.drop_table(&table) {
                         return Response::Error {
                             message: format!("drop_table {}: {}", table, e),
@@ -382,18 +561,48 @@ impl Server {
                             message: format!("drop_table {}: catalog save: {}", table, e),
                         };
                     }
-                }
+                    idx
+                };
 
                 self.tables.lock().unwrap().remove(&table);
                 let _ = std::fs::remove_file(self.table_path(&table));
-                let _ = std::fs::remove_file(self.index_path(&table));
+                let _ = std::fs::remove_file(self.index_path(&table, "id"));
+                for col in dropped_indexes {
+                    let _ = std::fs::remove_file(self.index_path(&table, &col));
+                }
 
                 Response::Ok
             }
+
+            Request::CreateIndex { table, column } => {
+                log_debug!(pipe, "create_index table={} column={}", table, column);
+                match self.create_index(&table, &column) {
+                    Ok(()) => Response::Ok,
+                    Err(e) => {
+                        log_warn!(pipe, "create_index {}({}): {}", table, column, e);
+                        Response::Error {
+                            message: format!("create_index {}({}): {}", table, column, e),
+                        }
+                    }
+                }
+            }
+
+            Request::DropIndex { table, column } => {
+                log_debug!(pipe, "drop_index table={} column={}", table, column);
+                match self.drop_index(&table, &column) {
+                    Ok(()) => Response::Ok,
+                    Err(e) => {
+                        log_warn!(pipe, "drop_index {}({}): {}", table, column, e);
+                        Response::Error {
+                            message: format!("drop_index {}({}): {}", table, column, e),
+                        }
+                    }
+                }
+            }
         }
     }
 
-// 信息查询
+    // 信息查询
     /// 表名：catalog 与目录取并集
     fn list_tables(&self) -> std::io::Result<Vec<String>> {
         let mut names = BTreeSet::new();
@@ -416,15 +625,23 @@ impl Server {
         Ok(names.into_iter().collect())
     }
 
-    /// 查一张表的 schema
-    fn describe_table(&self, table: &str) -> std::io::Result<(Vec<SchemaColumn>, u64)> {
+    /// 查一张表的 schema（列 + 行数 + 索引 + 统计）
+    fn describe_table(
+        &self,
+        table: &str,
+    ) -> std::io::Result<(Vec<SchemaColumn>, u64, Vec<IndexWire>, Vec<ColumnStatWire>)> {
         let c = self.catalog.lock().unwrap();
         if let Some(schema) = c.describe(table) {
-            return Ok((schema.columns.clone(), schema.row_count));
+            return Ok((
+                schema.columns.clone(),
+                schema.row_count,
+                index_wires(schema),
+                stat_wires(schema),
+            ));
         }
         drop(c);
         if std::fs::metadata(self.table_path(table)).is_ok() {
-            return Ok((Vec::new(), 0));
+            return Ok((Vec::new(), 0, Vec::new(), Vec::new()));
         }
         Err(std::io::Error::new(
             std::io::ErrorKind::NotFound,
@@ -433,6 +650,35 @@ impl Server {
     }
 }
 
+/// 一张表的索引定义 -> 线上格式。
+/// `id` 是内建索引（表一开出来就有），数据字典里不记它，但对外要报出来。
+fn index_wires(schema: &chusql_storage::catalog::TableSchema) -> Vec<IndexWire> {
+    let mut out = vec![IndexWire {
+        column: "id".to_string(),
+    }];
+    for i in &schema.indexes {
+        if i.column != "id" {
+            out.push(IndexWire {
+                column: i.column.clone(),
+            });
+        }
+    }
+    out
+}
+
+/// 一张表的列统计 -> 线上格式
+fn stat_wires(schema: &chusql_storage::catalog::TableSchema) -> Vec<ColumnStatWire> {
+    schema
+        .stats
+        .iter()
+        .map(|(name, s)| ColumnStatWire {
+            name: name.clone(),
+            distinct: s.distinct,
+            capped: s.capped,
+        })
+        .collect()
+}
+
 impl Drop for Server {
     fn drop(&mut self) {
         if let Ok(c) = self.catalog.lock() {
@@ -441,7 +687,6 @@ impl Drop for Server {
     }
 }
 
-
 // 连接
 /// 处理一条连接
 fn handle(server: &Server, conn: LocalSocketStream) -> std::io::Result<()> {
@@ -471,7 +716,6 @@ fn handle(server: &Server, conn: LocalSocketStream) -> std::io::Result<()> {
     Ok(())
 }
 
-
 // 入口
 /// 把配置来源打进日志
 fn log_config(loaded: &Loaded) {
@@ -506,6 +750,11 @@ fn main() -> std::io::Result<()> {
         return Err(e);
     }
 
+    if let Err(e) = server.rebuild_stats() {
+        // 统计重建失败不影响服务：报一声，继续跑（统计会停留在落盘时的值）
+        log_warn!(core, "stats rebuild skipped: {}", e);
+    }
+
     let ns_name = server
         .cfg
         .pipe_name
diff --git a/chusql-storage/src/btree.rs b/chusql-storage/src/btree.rs
index a9e06b5..995e953 100644
--- a/chusql-storage/src/btree.rs
+++ b/chusql-storage/src/btree.rs
@@ -430,6 +430,41 @@ impl DiskBTree {
         }
     }
 
+    /// 删掉一个键；键不存在返回 false。
+    ///
+    /// 这是**惰性删除**：只把叶子里那一对 (key, value) 拿掉，不做合并、也不向兄弟借位。
+    /// 于是树可能变稀、甚至留下空叶子，但查找依然正确——内部节点的分隔键仍然满足
+    /// "小于等于它的往左、大于它的往右"，空叶子二分找不到东西自然返回 None。
+    /// 代价是空间不回收（节点删空了也不还页），整表重写（`clear`）时会一起重建。
+    pub fn delete(&mut self, key: i64) -> io::Result<bool> {
+        match self.root()? {
+            None => Ok(false),
+            Some(r) => self.delete_rec(r, key),
+        }
+    }
+
+    /// 递归删除：一路走到叶子，删掉那一对
+    fn delete_rec(&mut self, page_id: PageId, key: i64) -> io::Result<bool> {
+        let order = self.order;
+        match self.file.with_page(page_id, |p| read_node(p, order))? {
+            NodeData::Leaf { mut keys, mut values, next } => match keys.binary_search(&key) {
+                Err(_) => Ok(false),
+                Ok(i) => {
+                    keys.remove(i);
+                    values.remove(i);
+                    self.file.update_page(page_id, |p| {
+                        write_node(p, &NodeData::Leaf { keys, values, next }, order)
+                    })?;
+                    Ok(true)
+                }
+            },
+            NodeData::Internal { keys, children } => {
+                let i = child_index(&keys, key);
+                self.delete_rec(children[i], key)
+            }
+        }
+    }
+
     /// 按键升序返回全部
     pub fn iter_all(&mut self) -> io::Result<Vec<(i64, u64)>> {
         let mut out = Vec::new();
diff --git a/chusql-storage/src/catalog.rs b/chusql-storage/src/catalog.rs
index 076a403..250393d 100644
--- a/chusql-storage/src/catalog.rs
+++ b/chusql-storage/src/catalog.rs
@@ -1,5 +1,7 @@
 
-use std::collections::BTreeMap;
+use std::collections::hash_map::DefaultHasher;
+use std::collections::{BTreeMap, HashSet};
+use std::hash::{Hash, Hasher};
 use std::io;
 use std::path::Path;
 
@@ -7,24 +9,52 @@ use serde::{Deserialize, Serialize};
 
 use crate::protocol::{ColumnType, Row, SchemaColumn};
 
-// 数据字典：记每张表有哪些列、什么类型、多少行。
+// 数据字典：记每张表有哪些列、什么类型、多少行、有哪些索引，以及列级统计。
+//
+// 统计只在内存里精确维护（每列见过哪些值的哈希，有上限），随 catalog.json 一起落盘；
+// 服务启动时会扫一遍表把统计重建出来，所以重启之后数字仍然是对的。
+
+/// 一列的不同值个数最多精确统计到这里；超过就只报"下界"
+const STATS_DISTINCT_CAP: u64 = 4096;
+
+// 表结构
+#[derive(Debug, Clone, Serialize, Deserialize)]
+/// 一条索引定义：只记"盯的是哪一列"（索引按列命名，一列最多一个）
+pub struct IndexSchema {
+    pub column: String,
+}
 
 #[derive(Debug, Clone, Default, Serialize, Deserialize)]
-/// 一张表的 schema
+/// 一列的统计
+pub struct ColumnStat {
+    /// 不同值个数（`capped` 为真时是下界）
+    pub distinct: u64,
+    /// 不同值太多，已经不再精确统计
+    #[serde(default)]
+    pub capped: bool,
+}
+
+#[derive(Debug, Clone, Default, Serialize, Deserialize)]
+/// 一张表的 schema + 统计
 pub struct TableSchema {
     pub columns: Vec<SchemaColumn>,
     #[serde(default)]
     pub row_count: u64,
+    #[serde(default)]
+    pub indexes: Vec<IndexSchema>,
+    #[serde(default)]
+    pub stats: BTreeMap<String, ColumnStat>,
 }
 
 #[derive(Debug, Default, Serialize, Deserialize)]
 /// 数据字典：表名到 schema
 pub struct Catalog {
     tables: BTreeMap<String, TableSchema>,
+    /// 每列"见过的值"的哈希集合（只在内存里，不落盘；有上限）
+    #[serde(skip)]
+    seen: BTreeMap<String, HashSet<u64>>,
 }
 
-
-
 impl Catalog {
     // 读取与保存
     /// 从文件读；不存在给空字典
@@ -65,17 +95,7 @@ impl Catalog {
     /// 按一行数据补列
     pub fn ensure_columns(&mut self, table: &str, row: &Row) {
         let entry = self.tables.entry(table.to_string()).or_default();
-        for (k, v) in row {
-            if entry.columns.iter().any(|c| &c.name == k) {
-                continue;
-            }
-            if let Some(ty) = infer_type(v) {
-                entry.columns.push(SchemaColumn {
-                    name: k.clone(),
-                    ty,
-                });
-            }
-        }
+        add_missing_columns(entry, row);
     }
 
     /// 建表；已存在报错
@@ -91,67 +111,144 @@ impl Catalog {
             TableSchema {
                 columns,
                 row_count: 0,
+                indexes: Vec::new(),
+                stats: BTreeMap::new(),
             },
         );
         Ok(())
     }
 
-    /// 按多行数据补列
-    pub fn ensure_columns_from_rows(&mut self, table: &str, rows: &[Row]) {
-        for r in rows {
-            self.ensure_columns(table, r);
-        }
-    }
-    /// 记一次插入：补列 + 行数 +1
+    /// 记一次插入：补列 + 行数 +1 + 更新列统计；返回"列有没有变化"（决定要不要立刻写盘）
     pub fn record_insert(&mut self, table: &str, row: &Row) -> bool {
-        let entry = self.tables.entry(table.to_string()).or_default();
-        let mut changed = false;
-        for (k, v) in row {
-            if entry.columns.iter().any(|c| &c.name == k) {
-                continue;
-            }
-            if let Some(ty) = infer_type(v) {
-                entry.columns.push(SchemaColumn { name: k.clone(), ty });
-                changed = true;
-            }
-        }
-        entry.row_count += 1;
+        let changed = {
+            let entry = self.tables.entry(table.to_string()).or_default();
+            let changed = add_missing_columns(entry, row);
+            entry.row_count += 1;
+            changed
+        };
+        self.count_values(table, row);
         changed
     }
 
-
-    /// 记一次整表替换：列照补，行数重置
-    pub fn record_replace_all(&mut self, table: &str, rows: &[Row]) -> bool {
+    /// 记一次删除：行数减少 + 更新列统计
+    pub fn record_delete(&mut self, table: &str, rows: &[Row]) {
         let entry = self.tables.entry(table.to_string()).or_default();
-        let mut changed = false;
+        entry.row_count = entry.row_count.saturating_sub(rows.len() as u64);
+        let seen = self.seen.entry(table.to_string()).or_default();
         for r in rows {
-            for (k, v) in r {
-                if entry.columns.iter().any(|c| &c.name == k) {
+            for (name, v) in r {
+                let stat = entry.stats.entry(name.clone()).or_default();
+                if stat.capped {
                     continue;
                 }
-                if let Some(ty) = infer_type(v) {
-                    entry.columns.push(SchemaColumn { name: k.clone(), ty });
-                    changed = true;
+                // 这个值彻底没了才减：集合里删得掉说明没有别的行还用它
+                if seen.remove(&fold(name, value_hash(v))) {
+                    stat.distinct = stat.distinct.saturating_sub(1);
+                }
+            }
+        }
+    }
+
+    /// 重数一遍统计与行数（启动时重建、整表改写完都走它）；返回"列有没有变化"
+    pub fn rebuild_stats(&mut self, table: &str, rows: &[Row]) -> bool {
+        self.seen.remove(table);
+        {
+            let entry = self.tables.entry(table.to_string()).or_default();
+            entry.stats.clear();
+            entry.row_count = 0;
+        }
+        // 逐行"插入"地数：行数、列、统计一次到位
+        rows.iter()
+            .fold(false, |changed, r| self.record_insert(table, r) || changed)
+    }
+
+    /// 列统计：这一列第一次见到这个值就 distinct +1（到上限之后只报下界）
+    fn count_values(&mut self, table: &str, row: &Row) {
+        let entry = self.tables.entry(table.to_string()).or_default();
+        let seen = self.seen.entry(table.to_string()).or_default();
+        for (name, v) in row {
+            let stat = entry.stats.entry(name.clone()).or_default();
+            if stat.capped {
+                continue;
+            }
+            if seen.insert(fold(name, value_hash(v))) {
+                stat.distinct += 1;
+                if stat.distinct >= STATS_DISTINCT_CAP {
+                    stat.capped = true;
+                    seen.clear(); // 到上限就不再精确统计，把内存还回去
                 }
             }
         }
-        entry.row_count = rows.len() as u64;
-        changed
     }
 
     /// 删表
-    pub fn drop_table(&mut self, table: &str) -> io::Result<()> {
-        if self.tables.remove(table).is_none() {
+    pub fn drop_table(&mut self, table: &str) -> io::Result<()> {        if self.tables.remove(table).is_none() {
             return Err(io::Error::new(
                 io::ErrorKind::NotFound,
                 format!("unknown table: {}", table),
             ));
         }
+        self.seen.remove(table);
         Ok(())
     }
+
+    // 索引
+    /// 记下一条索引定义
+    pub fn add_index(&mut self, table: &str, column: &str) -> io::Result<()> {
+        let entry = self
+            .tables
+            .get_mut(table)
+            .ok_or_else(|| io::Error::new(io::ErrorKind::NotFound, format!("unknown table: {}", table)))?;
+        if entry.indexes.iter().any(|i| i.column == column) {
+            return Err(io::Error::new(
+                io::ErrorKind::AlreadyExists,
+                format!("index on column \"{}\" already exists", column),
+            ));
+        }
+        entry.indexes.push(IndexSchema {
+            column: column.to_string(),
+        });
+        Ok(())
+    }
+
+    /// 去掉一条索引定义
+    pub fn remove_index(&mut self, table: &str, column: &str) -> io::Result<()> {
+        let entry = self
+            .tables
+            .get_mut(table)
+            .ok_or_else(|| io::Error::new(io::ErrorKind::NotFound, format!("unknown table: {}", table)))?;
+        match entry.indexes.iter().position(|i| i.column == column) {
+            None => Err(io::Error::new(
+                io::ErrorKind::NotFound,
+                format!("no index on column \"{}\"", column),
+            )),
+            Some(i) => {
+                entry.indexes.remove(i);
+                Ok(())
+            }
+        }
+    }
 }
 
 // 推断
+/// 把行里"字典还不知道的列"补进来；返回有没有变化
+fn add_missing_columns(entry: &mut TableSchema, row: &Row) -> bool {
+    let mut changed = false;
+    for (k, v) in row {
+        if entry.columns.iter().any(|c| &c.name == k) {
+            continue;
+        }
+        if let Some(ty) = infer_type(v) {
+            entry.columns.push(SchemaColumn {
+                name: k.clone(),
+                ty,
+            });
+            changed = true;
+        }
+    }
+    changed
+}
+
 /// 由 JSON 值猜列类型
 fn infer_type(v: &serde_json::Value) -> Option<ColumnType> {
     match v {
@@ -161,3 +258,18 @@ fn infer_type(v: &serde_json::Value) -> Option<ColumnType> {
         _ => None,
     }
 }
+
+/// 一个值的哈希（按它的 JSON 文本算；统计"不同值个数"用）
+fn value_hash(v: &serde_json::Value) -> u64 {
+    let mut h = DefaultHasher::new();
+    v.to_string().hash(&mut h);
+    h.finish()
+}
+
+/// 把"列名"和"值哈希"合成一个哈希：避免两列的同值互相干扰
+fn fold(column: &str, value_hash: u64) -> u64 {
+    let mut h = DefaultHasher::new();
+    column.hash(&mut h);
+    value_hash.hash(&mut h);
+    h.finish()
+}
diff --git a/chusql-storage/src/heap.rs b/chusql-storage/src/heap.rs
index f7cc6df..c19e599 100644
--- a/chusql-storage/src/heap.rs
+++ b/chusql-storage/src/heap.rs
@@ -1,3 +1,4 @@
+use std::collections::HashSet;
 use std::io;
 use std::path::Path;
 
@@ -6,7 +7,10 @@ use crate::page::PageId;
 use crate::page::{Page, PageFile};
 use crate::protocol::Row;
 
-// 堆表：行按插入顺序进页，支持全表扫描与按索引取行。
+// 堆表：行按插入顺序进页，支持全表扫描、按索引取行、行级删除。
+//
+// 索引由**表自己维护**：有哪些索引记在数据字典里，插入时按索引的列从行里取值写进去，
+// 调用方不需要知道有哪些索引，也不需要自己指定 key。
 
 // 页内布局
 /// 页头：slot_count 占 2 字节
@@ -47,6 +51,14 @@ fn unpack_position(v: u64) -> (PageId, u16) {
     (v >> 16, (v & 0xFFFF) as u16)
 }
 
+/// 取行里某一列的整数值（不是整数就没有）
+fn row_int(row: &Row, column: &str) -> Option<i64> {
+    match row.get(column) {
+        Some(serde_json::Value::Number(n)) => n.as_i64(),
+        _ => None,
+    }
+}
+
 // 页内操作
 /// 只管一页里的字节
 pub struct HeapPage;
@@ -103,6 +115,20 @@ impl HeapPage {
         Some(n)
     }
 
+    /// 删掉一个槽位：只把长度置 0，行字节原地留着（读的时候按"长度 0 = 没有这一行"处理）
+    pub fn delete_tuple(page: &mut Page, slot: u16) -> bool {
+        let n = Self::slot_count(page);
+        if slot >= n {
+            return false;
+        }
+        let slot_off = SLOT_DIR_START + (slot as usize) * SLOT_SIZE;
+        if read_u32(&page.data, slot_off + 4) == 0 {
+            return false;
+        }
+        write_u32(&mut page.data, slot_off + 4, 0);
+        true
+    }
+
     /// 读槽位里的行字节
     pub fn get_tuple(page: &Page, slot: u16) -> Option<Vec<u8>> {
         let n = Self::slot_count(page);
@@ -124,27 +150,30 @@ impl HeapPage {
     }
 }
 
+// 索引
+/// 表上的一个索引：盯着一列，键是这一列的整数值
+struct NamedIndex {
+    column: String,
+    tree: DiskBTree,
+}
+
 // 堆表
-/// 一个文件 = 若干页
+/// 一个数据文件 = 若干页；外加若干索引文件
 pub struct HeapTable {
     file: PageFile,
-    index: Option<DiskBTree>,
+    indexes: Vec<NamedIndex>,
 }
 
 impl HeapTable {
     /// 打开表（不带索引）
-    pub fn open<P: AsRef<Path>>(
-        path: P,
-        page_size: usize,
-        pool_size: usize,
-    ) -> io::Result<Self> {
-         Ok(HeapTable {
+    pub fn open<P: AsRef<Path>>(path: P, page_size: usize, pool_size: usize) -> io::Result<Self> {
+        Ok(HeapTable {
             file: PageFile::with_options(path, page_size, pool_size)?,
-            index: None,
+            indexes: Vec::new(),
         })
     }
 
-    /// 打开表 + 索引
+    /// 打开表 + `id` 列索引（`id` 沿用老文件名 `表名.idx`）
     pub fn open_indexed<P: AsRef<Path>, Q: AsRef<Path>>(
         path: P,
         index_path: Q,
@@ -152,19 +181,155 @@ impl HeapTable {
         btree_order: usize,
         pool_size: usize,
     ) -> io::Result<Self> {
-        Ok(HeapTable {
+        let mut t = HeapTable {
             file: PageFile::with_options(path, page_size, pool_size)?,
-            index: Some(DiskBTree::open(index_path, page_size, btree_order, pool_size)?),
-        })
+            indexes: Vec::new(),
+        };
+        t.attach_index("id", index_path, page_size, btree_order, pool_size)?;
+        Ok(t)
     }
 
-    /// 插入一行，不更新索引
-    pub fn insert(&mut self, row: &Row) -> io::Result<()> {
-        self.insert_returning_position(row).map(|_| ())
+    /// 打开表 + 任意组索引：(列名, 索引文件路径)
+    pub fn open_with_indexes<P: AsRef<Path>>(
+        path: P,
+        indexes: &[(String, std::path::PathBuf)],
+        page_size: usize,
+        btree_order: usize,
+        pool_size: usize,
+    ) -> io::Result<Self> {
+        let mut t = HeapTable {
+            file: PageFile::with_options(path, page_size, pool_size)?,
+            indexes: Vec::new(),
+        };
+        for (col, p) in indexes {
+            t.attach_index(col, p, page_size, btree_order, pool_size)?;
+        }
+        Ok(t)
     }
 
-    /// 插入并返回行位置
-    pub fn insert_returning_position(&mut self, row: &Row) -> io::Result<(PageId, u16)> {
+    /// 挂上一棵索引树（只打开/创建文件，不填数据）
+    fn attach_index<P: AsRef<Path>>(
+        &mut self,
+        column: &str,
+        path: P,
+        page_size: usize,
+        btree_order: usize,
+        pool_size: usize,
+    ) -> io::Result<()> {
+        let tree = DiskBTree::open(path, page_size, btree_order, pool_size)?;
+        self.indexes.push(NamedIndex {
+            column: column.to_string(),
+            tree,
+        });
+        Ok(())
+    }
+
+    /// 这一列有索引吗
+    pub fn has_index(&self, column: &str) -> bool {
+        self.indexes.iter().any(|i| i.column == column)
+    }
+
+    /// 建索引：先扫一遍查重，再建树填数据。
+    ///
+    /// **要求这一列的整数取值唯一**，不唯一就报错、一个索引文件都不留。
+    /// 这样"走索引取一行"和"全表扫一遍再筛"必然得到同一个答案；
+    /// 非唯一索引要等 B+ 树支持重复键（记在项目计划的 P2-② 里）。
+    pub fn build_index(
+        &mut self,
+        column: &str,
+        path: &Path,
+        page_size: usize,
+        btree_order: usize,
+        pool_size: usize,
+    ) -> io::Result<()> {
+        if self.has_index(column) {
+            return Err(io::Error::new(
+                io::ErrorKind::AlreadyExists,
+                format!("index on column \"{}\" already exists", column),
+            ));
+        }
+
+        // 第 1 步：扫全表，查重并攒下 (键, 位置)
+        let mut seen: HashSet<i64> = HashSet::new();
+        let mut entries: Vec<(i64, u64)> = Vec::new();
+        for (page_id, slot, r) in self.scan_with_positions()? {
+            let Some(k) = row_int(&r, column) else {
+                continue; // 这一列不是整数的行不进索引
+            };
+            if !seen.insert(k) {
+                return Err(io::Error::new(
+                    io::ErrorKind::InvalidInput,
+                    format!(
+                        "column \"{}\" has duplicate value {} — 暂不支持非唯一索引",
+                        column, k
+                    ),
+                ));
+            }
+            entries.push((k, pack_position(page_id, slot)));
+        }
+
+        // 第 2 步：建树
+        self.attach_index(column, path, page_size, btree_order, pool_size)?;
+        let i = self.indexes.len() - 1;
+        self.indexes[i].tree.clear()?; // 清掉可能残留的旧文件内容
+        for (k, pos) in entries {
+            self.indexes[i].tree.insert(k, pos)?;
+        }
+        Ok(())
+    }
+
+    /// 摘掉一个索引（不删文件）
+    pub fn detach_index(&mut self, column: &str) -> bool {
+        match self.indexes.iter().position(|i| i.column == column) {
+            None => false,
+            Some(i) => {
+                self.indexes.remove(i);
+                true
+            }
+        }
+    }
+
+    /// 插入一行：进堆表，并按每个索引的列顺手写索引
+    pub fn insert_row(&mut self, row: &Row) -> io::Result<()> {
+        self.insert_row_returning_position(row).map(|_| ())
+    }
+
+    /// 插入一行并返回它的位置
+    pub fn insert_row_returning_position(&mut self, row: &Row) -> io::Result<(PageId, u16)> {
+        // 先把键算好并查重：**查重必须在落堆之前**，
+        // 否则某个索引写不进去时行已经进堆了，表和索引就不一致了。
+        let mut pending: Vec<(usize, i64)> = Vec::new();
+        for (i, idx) in self.indexes.iter_mut().enumerate() {
+            let Some(k) = row_int(row, &idx.column) else {
+                continue; // 这一列不是整数（或没这一列）：这行不进这个索引
+            };
+            if idx.tree.get(k)?.is_some() {
+                return Err(io::Error::new(
+                    io::ErrorKind::InvalidInput,
+                    format!("duplicate key {} on indexed column \"{}\"", k, idx.column),
+                ));
+            }
+            pending.push((i, k));
+        }
+
+        let (page_id, slot) = self.insert_returning_position(row)?;
+        let pos = pack_position(page_id, slot);
+        for (i, k) in pending {
+            self.indexes[i].tree.insert(k, pos)?;
+        }
+        Ok((page_id, slot))
+    }
+
+    /// 批量插入（只写缓冲池，落盘由调用方 `flush` 一次完成）
+    pub fn insert_rows(&mut self, rows: &[Row]) -> io::Result<()> {
+        for r in rows {
+            self.insert_row(r)?;
+        }
+        Ok(())
+    }
+
+    /// 插入一行，只进堆表、不碰索引
+    fn insert_returning_position(&mut self, row: &Row) -> io::Result<(PageId, u16)> {
         let tuple = serde_json::to_vec(row).map_err(io::Error::other)?;
 
         if HEADER_SIZE + SLOT_SIZE + tuple.len() > self.file.page_size() {
@@ -193,23 +358,18 @@ impl HeapTable {
         Ok((page_id, slot))
     }
 
-    /// 插入一行并写索引
-    pub fn insert_keyed(&mut self, row: &Row, key: i64) -> io::Result<()> {
-        let (page_id, slot) = self.insert_returning_position(row)?;
-        if let Some(idx) = &mut self.index {
-            idx.insert(key, pack_position(page_id, slot))?;
-        }
-        Ok(())
+    /// 按 `id` 取一行
+    pub fn get_by_key(&mut self, key: i64) -> io::Result<Option<Row>> {
+        self.get_by_column_key("id", key)
     }
 
-    /// 按索引键取一行
-    pub fn get_by_key(&mut self, key: i64) -> io::Result<Option<Row>> {
-        let pos = match &mut self.index {
-            None => return Ok(None),
-            Some(idx) => match idx.get(key)? {
-                None => return Ok(None),
-                Some(p) => p,
-            },
+    /// 按某一列的索引取一行
+    pub fn get_by_column_key(&mut self, column: &str, key: i64) -> io::Result<Option<Row>> {
+        let Some(idx) = self.indexes.iter_mut().find(|i| i.column == column) else {
+            return Ok(None);
+        };
+        let Some(pos) = idx.tree.get(key)? else {
+            return Ok(None);
         };
         let (page_id, slot) = unpack_position(pos);
         self.read_at(page_id, slot)
@@ -227,47 +387,115 @@ impl HeapTable {
         }
     }
 
-    /// 全表扫描
-    pub fn scan(&mut self) -> io::Result<Vec<Row>> {
-        let n = self.file.num_pages()?;
-        let mut rows = Vec::new();
-        for i in 0..n {
-            let tuples = self.file.with_page(i, |p| {
-                let mut out = Vec::new();
-                for slot in HeapPage::iter_slots(p) {
-                    if let Some(bytes) = HeapPage::get_tuple(p, slot) {
-                        out.push(bytes);
-                    }
+    /// 按位置删一行：槽位长度置 0，从所有索引里摘掉，并把这一行交出来
+    pub fn delete_at(&mut self, page_id: PageId, slot: u16) -> io::Result<Option<Row>> {
+        // 先读出来：删完就不知道这行各列是什么，索引也就无从摘起
+        let row = self.read_at(page_id, slot)?;
+        let existed = self.file.update_page(page_id, |p| HeapPage::delete_tuple(p, slot))?;
+        if !existed {
+            return Ok(None);
+        }
+        if let Some(r) = &row {
+            for idx in &mut self.indexes {
+                if let Some(k) = row_int(r, &idx.column) {
+                    idx.tree.delete(k)?;
                 }
-                out
-            })?;
-            for bytes in tuples {
-                let row: Row = serde_json::from_slice(&bytes).map_err(io::Error::other)?;
-                rows.push(row);
             }
         }
-        Ok(rows)
+        Ok(row)
     }
 
-    /// 整表改写并重建索引
+    /// 按 `id` 批量删行，返回被删掉的那些行（数据字典要用它更新统计）。
+    ///
+    /// 定位靠 `id` 索引；没有这个索引就退化成一趟全表扫描（仍然只删目标行）。
+    pub fn delete_by_keys(&mut self, keys: &[i64]) -> io::Result<Vec<Row>> {
+        let mut positions: Vec<(PageId, u16)> = Vec::new();
+
+        if self.has_index("id") {
+            for &k in keys {
+                let pos = self
+                    .indexes
+                    .iter_mut()
+                    .find(|i| i.column == "id")
+                    .and_then(|i| i.tree.get(k).ok().flatten());
+                if let Some(p) = pos {
+                    positions.push(unpack_position(p));
+                }
+            }
+        } else {
+            let mut wanted: Vec<i64> = keys.to_vec();
+            wanted.sort_unstable();
+            for (page_id, slot, r) in self.scan_with_positions()? {
+                if let Some(k) = row_int(&r, "id") {
+                    if wanted.binary_search(&k).is_ok() {
+                        positions.push((page_id, slot));
+                    }
+                }
+            }
+        }
+
+        let mut deleted: Vec<Row> = Vec::new();
+        for (page_id, slot) in positions {
+            if let Some(r) = self.delete_at(page_id, slot)? {
+                deleted.push(r);
+            }
+        }
+        Ok(deleted)
+    }
+
+    /// 全表扫描
+    pub fn scan(&mut self) -> io::Result<Vec<Row>> {
+        Ok(self
+            .scan_with_positions()?
+            .into_iter()
+            .map(|(_, _, r)| r)
+            .collect())
+    }
+
+    /// 全表扫描，同时给出每行的位置（建索引用）
+    pub fn scan_with_positions(&mut self) -> io::Result<Vec<(PageId, u16, Row)>> {
+        let n = self.file.num_pages()?;
+        let mut out = Vec::new();
+        for i in 0..n {
+            let tuples = self.file.with_page(i, |p| {
+                let mut v = Vec::new();
+                for slot in HeapPage::iter_slots(p) {
+                    if let Some(bytes) = HeapPage::get_tuple(p, slot) {
+                        v.push((slot, bytes));
+                    }
+                }
+                v
+            })?;
+            for (slot, bytes) in tuples {
+                let row: Row = serde_json::from_slice(&bytes).map_err(io::Error::other)?;
+                out.push((i, slot, row));
+            }
+        }
+        Ok(out)
+    }
+
+    /// 整表改写并重建所有索引
     pub fn replace_all(&mut self, rows: &[Row]) -> io::Result<()> {
         self.file.truncate()?;
-        if let Some(idx) = &mut self.index {
-            idx.clear()?;
+        for idx in &mut self.indexes {
+            idx.tree.clear()?;
         }
         for r in rows {
             let (page_id, slot) = self.insert_returning_position(r)?;
-            if let (Some(idx), Some(key)) = (&mut self.index, row_key(r)) {
-                idx.insert(key, pack_position(page_id, slot))?;
+            let pos = pack_position(page_id, slot);
+            for idx in &mut self.indexes {
+                if let Some(k) = row_int(r, &idx.column) {
+                    idx.tree.insert(k, pos)?;
+                }
             }
         }
         Ok(())
     }
 
-    /// 把脏页写回
+    /// 把脏页写回（索引也一起）
     pub fn flush(&mut self) -> io::Result<()> {
-        if let Some(idx) = &mut self.index {
-            idx.flush()?;
+        for idx in &mut self.indexes {
+            idx.tree.flush()?;
         }
         self.file.flush()
     }
@@ -282,11 +510,3 @@ impl HeapTable {
     /// 命中率
     pub fn hit_rate(&self) -> f64 { self.file.hit_rate() }
 }
-
-/// 取行里的 id 作索引键
-fn row_key(row: &Row) -> Option<i64> {
-    match row.get("id") {
-        Some(serde_json::Value::Number(n)) => n.as_i64(),
-        _ => None,
-    }
-}
diff --git a/chusql-storage/src/protocol.rs b/chusql-storage/src/protocol.rs
index 7af16eb..d1163f8 100644
--- a/chusql-storage/src/protocol.rs
+++ b/chusql-storage/src/protocol.rs
@@ -22,42 +22,104 @@ pub struct SchemaColumn {
     pub ty: ColumnType,
 }
 
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+/// 一列的统计（随数据字典一起走）
+pub struct ColumnStatWire {
+    pub name: String,
+    /// 不同值个数；`capped` 为真时它只是下界
+    pub distinct: u64,
+    #[serde(default)]
+    pub capped: bool,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+/// 一条索引定义
+pub struct IndexWire {
+    pub column: String,
+}
+
 #[derive(Debug, Serialize, Deserialize)]
 #[serde(tag = "method", rename_all = "snake_case")]
 /// 请求：method 字段决定类型
 pub enum Request {
     Ping,
-    Scan { table: String },
+    Scan {
+        table: String,
+    },
+    /// 插一行；要不要写索引由表上的索引决定（调用方不用管）
     Insert {
         table: String,
         row: Row,
-        #[serde(default)]
-        key: Option<i64>,
     },
-    LookupByIndex { table: String, key: i64 },
-    ReplaceAll { table: String, rows: Vec<Row> },
+    /// 一批行一起插：一次 WAL、一次 fsync
+    InsertBatch {
+        table: String,
+        rows: Vec<Row>,
+    },
+    /// 按 id 批量删行
+    DeleteKeys {
+        table: String,
+        keys: Vec<i64>,
+    },
+    /// 按某一列的索引取一行（列名默认 "id"，兼容老客户端）
+    LookupByIndex {
+        table: String,
+        #[serde(default = "default_id_column")]
+        column: String,
+        key: i64,
+    },
+    ReplaceAll {
+        table: String,
+        rows: Vec<Row>,
+    },
     ListTables,
-    DescribeTable { table: String },
+    DescribeTable {
+        table: String,
+    },
     CreateTable {
         table: String,
         columns: Vec<SchemaColumn>,
     },
-    DropTable { table: String },
-    ListCatalog
+    DropTable {
+        table: String,
+    },
+    ListCatalog,
+    /// 给某一列建索引（要求这一列整数取值唯一）
+    CreateIndex {
+        table: String,
+        column: String,
+    },
+    /// 去掉某一列的索引
+    DropIndex {
+        table: String,
+        column: String,
+    },
+}
+
+/// 没写 column 时按 `id` 算
+fn default_id_column() -> String {
+    "id".to_string()
 }
 
 #[derive(Debug, Serialize, Deserialize)]
-#[serde(tag = "status", rename_all = "lowercase")]
+#[serde(tag = "status", rename_all = "snake_case")]
 /// 响应：status 字段决定类型
 pub enum Response {
     Pong,
     Rows { rows: Vec<Row> },
     Tables { tables: Vec<String> },
     Schema {
+        table: String,
         columns: Vec<SchemaColumn>,
         #[serde(default)]
         row_count: u64,
+        #[serde(default)]
+        indexes: Vec<IndexWire>,
+        #[serde(default)]
+        stats: Vec<ColumnStatWire>,
     },
+    /// 这一列没有索引 —— 调用方应该退回全表扫描
+    NoIndex,
     Ok,
     Error { message: String },
     Catalog { schemas: Vec<TableSchemaWire> },
@@ -69,4 +131,8 @@ pub struct TableSchemaWire {
     pub columns: Vec<SchemaColumn>,
     #[serde(default)]
     pub row_count: u64,
+    #[serde(default)]
+    pub indexes: Vec<IndexWire>,
+    #[serde(default)]
+    pub stats: Vec<ColumnStatWire>,
 }
diff --git a/chusql-storage/src/wal.rs b/chusql-storage/src/wal.rs
index 2b2afab..b0dadb7 100644
--- a/chusql-storage/src/wal.rs
+++ b/chusql-storage/src/wal.rs
@@ -1,7 +1,8 @@
 
 use std::fs::{File, OpenOptions};
-use std::io::{self, Read, Write};
+use std::io::{self, Read, Seek, SeekFrom, Write};
 use std::path::{Path, PathBuf};
+use std::sync::Mutex;
 
 use serde::{Deserialize, Serialize};
 
@@ -11,6 +12,8 @@ use crate::protocol::Row;
 
 const OP_INSERT: u8 = 1;
 const OP_REPLACE_ALL: u8 = 2;
+const OP_INSERT_BATCH: u8 = 3;
+const OP_DELETE_KEYS: u8 = 4;
 
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
 /// 一条待写入的操作
@@ -18,7 +21,16 @@ pub enum WalOp {
     Insert {
         table: String,
         row: Row,
-        key: Option<i64>,
+    },
+    /// 一批行：一次日志、一次 fsync 就能全部落盘
+    InsertBatch {
+        table: String,
+        rows: Vec<Row>,
+    },
+    /// 按 id 批量删行（重放是幂等的：再删一次等于什么都没删）
+    DeleteKeys {
+        table: String,
+        keys: Vec<i64>,
     },
     ReplaceAll {
         table: String,
@@ -27,8 +39,13 @@ pub enum WalOp {
 }
 
 /// WAL 文件
+///
+/// 句柄只开一次并一直留着：写入路径是每条操作一次
+/// `truncate -> append -> truncate`，每次都重新 open/close 文件要多花
+/// 一倍的时间（见 benchmark/chusql-storage）。
 pub struct Wal {
     path: PathBuf,
+    handle: Mutex<Option<File>>,
 }
 
 impl Wal {
@@ -37,6 +54,7 @@ impl Wal {
     pub fn new<P: AsRef<Path>>(path: P) -> Self {
         Wal {
             path: path.as_ref().to_path_buf(),
+            handle: Mutex::new(None),
         }
     }
 
@@ -45,26 +63,43 @@ impl Wal {
         &self.path
     }
 
-    /// 清空 WAL
-    pub fn clear(&self) -> io::Result<()> {
-        if self.path.exists() {
-            let f = OpenOptions::new().write(true).open(&self.path)?;
-            f.set_len(0)?;
-            f.sync_all()?;
+    /// 拿常驻句柄（没有就开一个）
+    fn with_handle<R>(&self, f: impl FnOnce(&mut File) -> io::Result<R>) -> io::Result<R> {
+        let mut slot = self.handle.lock().unwrap();
+        if slot.is_none() {
+            *slot = Some(
+                OpenOptions::new()
+                    .read(true)
+                    .write(true)
+                    .create(true)
+                    .truncate(false)
+                    .open(&self.path)?,
+            );
         }
-        Ok(())
+        f(slot.as_mut().expect("just opened"))
+    }
+
+    /// 截断到空并落盘
+    pub fn clear(&self) -> io::Result<()> {
+        self.with_handle(|f| {
+            truncate(f)?;
+            f.sync_all()
+        })
+    }
+
+    /// 只截断、不落盘：紧跟其后的 `append` 会 fsync，
+    /// 那一次会把截断一起落下去，所以这里不必单独再刷一遍。
+    pub fn truncate(&self) -> io::Result<()> {
+        self.with_handle(truncate)
     }
 
     /// 追加一条并 fsync
     pub fn append(&self, op: &WalOp) -> io::Result<()> {
         let bytes = encode(op)?;
-        let mut f = OpenOptions::new()
-            .create(true)
-            .append(true)
-            .open(&self.path)?;
-        f.write_all(&bytes)?;
-        f.sync_data()?;
-        Ok(())
+        self.with_handle(|f| {
+            f.write_all(&bytes)?;
+            f.sync_data()
+        })
     }
 
     /// 读当前 WAL；空则 None
@@ -88,14 +123,29 @@ impl Wal {
     }
 }
 
+/// 清空文件并回到起点（句柄不是 append 模式，位置要自己摆正）
+fn truncate(f: &mut File) -> io::Result<()> {
+    f.set_len(0)?;
+    f.seek(SeekFrom::Start(0))?;
+    Ok(())
+}
+
 // 编解码
 /// 把操作编成字节
 fn encode(op: &WalOp) -> io::Result<Vec<u8>> {
     let (op_type, table, payload) = match op {
-        WalOp::Insert { table, row, key } => {
-            let p = serde_json::to_vec(&(row, key)).map_err(io::Error::other)?;
+        WalOp::Insert { table, row } => {
+            let p = serde_json::to_vec(row).map_err(io::Error::other)?;
             (OP_INSERT, table.clone(), p)
         }
+        WalOp::InsertBatch { table, rows } => {
+            let p = serde_json::to_vec(rows).map_err(io::Error::other)?;
+            (OP_INSERT_BATCH, table.clone(), p)
+        }
+        WalOp::DeleteKeys { table, keys } => {
+            let p = serde_json::to_vec(keys).map_err(io::Error::other)?;
+            (OP_DELETE_KEYS, table.clone(), p)
+        }
         WalOp::ReplaceAll { table, rows } => {
             let p = serde_json::to_vec(rows).map_err(io::Error::other)?;
             (OP_REPLACE_ALL, table.clone(), p)
@@ -145,9 +195,19 @@ fn decode(buf: &[u8]) -> Result<Option<WalOp>, String> {
 
     let op = match op_type {
         OP_INSERT => {
-            let (row, key): (Row, Option<i64>) = serde_json::from_slice(payload)
-                .map_err(|e| format!("bad insert payload: {}", e))?;
-            WalOp::Insert { table, row, key }
+            let row: Row =
+                serde_json::from_slice(payload).map_err(|e| format!("bad insert payload: {}", e))?;
+            WalOp::Insert { table, row }
+        }
+        OP_INSERT_BATCH => {
+            let rows: Vec<Row> = serde_json::from_slice(payload)
+                .map_err(|e| format!("bad insert_batch payload: {}", e))?;
+            WalOp::InsertBatch { table, rows }
+        }
+        OP_DELETE_KEYS => {
+            let keys: Vec<i64> = serde_json::from_slice(payload)
+                .map_err(|e| format!("bad delete_keys payload: {}", e))?;
+            WalOp::DeleteKeys { table, keys }
         }
         OP_REPLACE_ALL => {
             let rows: Vec<Row> = serde_json::from_slice(payload)
diff --git a/chusql-storage/tests/btree_test.rs b/chusql-storage/tests/btree_test.rs
index 38442f9..5dcfddc 100644
--- a/chusql-storage/tests/btree_test.rs
+++ b/chusql-storage/tests/btree_test.rs
@@ -153,3 +153,63 @@ fn order_too_large_for_page_errors() {
     let dir = tempfile::tempdir().unwrap();
     assert!(DiskBTree::open(dir.path().join("t.idx"), 512, 300, DEFAULT_POOL_SIZE).is_err());
 }
+
+/// 删掉键之后查不到，别人不受影响
+#[test]
+fn delete_removes_only_that_key() {
+    let dir = tempfile::tempdir().unwrap();
+    let mut t = DiskBTree::open(
+        dir.path().join("t.idx"),
+        DEFAULT_PAGE_SIZE,
+        DEFAULT_BTREE_ORDER,
+        DEFAULT_POOL_SIZE,
+    )
+    .unwrap();
+    for i in 0..200 {
+        t.insert(i, i as u64 + 1).unwrap();
+    }
+
+    assert!(t.delete(50).unwrap(), "删一个存在的键应该返回 true");
+    assert_eq!(t.get(50).unwrap(), None);
+    assert_eq!(t.get(49).unwrap(), Some(50));
+    assert_eq!(t.get(51).unwrap(), Some(52));
+
+    // 再删一次：它已经不在了
+    assert!(!t.delete(50).unwrap());
+
+    // 遍历里也不能再有它
+    let all = t.iter_all().unwrap();
+    assert_eq!(all.len(), 199);
+    assert!(all.iter().all(|(k, _)| *k != 50));
+}
+
+/// 删过之后树还能继续插（惰性删除会留下稀疏节点，但不能影响正确性）
+#[test]
+fn insert_after_delete_still_works() {
+    let dir = tempfile::tempdir().unwrap();
+    let mut t = DiskBTree::open(
+        dir.path().join("t.idx"),
+        DEFAULT_PAGE_SIZE,
+        DEFAULT_BTREE_ORDER,
+        DEFAULT_POOL_SIZE,
+    )
+    .unwrap();
+    for i in 0..300 {
+        t.insert(i, i as u64).unwrap();
+    }
+    // 把偶数键全删掉
+    for i in (0..300).step_by(2) {
+        assert!(t.delete(i).unwrap());
+    }
+    // 再插一批新的
+    for i in 1000..1100 {
+        t.insert(i, i as u64).unwrap();
+    }
+    for i in 0..300 {
+        let want = if i % 2 == 0 { None } else { Some(i as u64) };
+        assert_eq!(t.get(i).unwrap(), want, "key {}", i);
+    }
+    for i in 1000..1100 {
+        assert_eq!(t.get(i).unwrap(), Some(i as u64));
+    }
+}
diff --git a/chusql-storage/tests/heap_test.rs b/chusql-storage/tests/heap_test.rs
index 624113b..6c8eb3c 100644
--- a/chusql-storage/tests/heap_test.rs
+++ b/chusql-storage/tests/heap_test.rs
@@ -21,7 +21,7 @@ fn insert_and_scan_one_row() {
     let path = dir.path().join("t.db");
     let mut t = HeapTable::open(&path, DEFAULT_PAGE_SIZE, DEFAULT_POOL_SIZE).unwrap();
 
-    t.insert(&row(&[("id", json!(1)), ("name", json!("Alice"))]))
+    t.insert_row(&row(&[("id", json!(1)), ("name", json!("Alice"))]))
         .unwrap();
 
     let rows = t.scan().unwrap();
@@ -38,7 +38,7 @@ fn insert_many_rows_cross_pages() {
     let mut t = HeapTable::open(&path, DEFAULT_PAGE_SIZE, DEFAULT_POOL_SIZE).unwrap();
 
     for i in 0..500 {
-        t.insert(&row(&[("id", json!(i))])).unwrap();
+        t.insert_row(&row(&[("id", json!(i))])).unwrap();
     }
 
     let rows = t.scan().unwrap();
@@ -56,7 +56,7 @@ fn large_row_still_fits() {
     let mut t = HeapTable::open(&path, DEFAULT_PAGE_SIZE, DEFAULT_POOL_SIZE).unwrap();
 
     let big = "x".repeat(2000);
-    t.insert(&row(&[("data", json!(big.clone()))])).unwrap();
+    t.insert_row(&row(&[("data", json!(big.clone()))])).unwrap();
 
     let rows = t.scan().unwrap();
     assert_eq!(rows.len(), 1);
@@ -71,7 +71,7 @@ fn row_too_large_errors() {
     let mut t = HeapTable::open(&path, DEFAULT_PAGE_SIZE, DEFAULT_POOL_SIZE).unwrap();
 
     let huge = "x".repeat(10_000);
-    let err = t.insert(&row(&[("data", json!(huge))]));
+    let err = t.insert_row(&row(&[("data", json!(huge))]));
     assert!(err.is_err());
 }
 
@@ -83,8 +83,8 @@ fn reopen_and_scan() {
 
     {
         let mut t = HeapTable::open(&path, DEFAULT_PAGE_SIZE, DEFAULT_POOL_SIZE).unwrap();
-        t.insert(&row(&[("id", json!(1))])).unwrap();
-        t.insert(&row(&[("id", json!(2))])).unwrap();
+        t.insert_row(&row(&[("id", json!(1))])).unwrap();
+        t.insert_row(&row(&[("id", json!(2))])).unwrap();
     }
 
     let mut t = HeapTable::open(&path, DEFAULT_PAGE_SIZE, DEFAULT_POOL_SIZE).unwrap();
@@ -102,12 +102,12 @@ fn custom_page_size() {
     let mut t = HeapTable::open(&path, 512, DEFAULT_POOL_SIZE).unwrap();
 
     for i in 0..50 {
-        t.insert(&row(&[("id", json!(i))])).unwrap();
+        t.insert_row(&row(&[("id", json!(i))])).unwrap();
     }
     assert_eq!(t.scan().unwrap().len(), 50);
 
     let big = "x".repeat(600);
-    assert!(t.insert(&row(&[("data", json!(big))])).is_err());
+    assert!(t.insert_row(&row(&[("data", json!(big))])).is_err());
 }
 
 /// 整表改写后索引重建
@@ -123,9 +123,9 @@ fn replace_all_rebuilds_index() {
     )
     .unwrap();
 
-    t.insert_keyed(&row(&[("id", json!(1)), ("name", json!("Alice"))]), 1)
+    t.insert_row(&row(&[("id", json!(1)), ("name", json!("Alice"))]))
         .unwrap();
-    t.insert_keyed(&row(&[("id", json!(2)), ("name", json!("Bob"))]), 2)
+    t.insert_row(&row(&[("id", json!(2)), ("name", json!("Bob"))]))
         .unwrap();
     assert!(t.get_by_key(1).unwrap().is_some());
 
@@ -141,3 +141,150 @@ fn replace_all_rebuilds_index() {
     assert_eq!(got["name"], json!("Zoe"));
     assert_eq!(t.scan().unwrap().len(), 2);
 }
+
+/// 行级删除：行没了、索引条目没了、顺序不乱
+#[test]
+fn delete_by_keys_removes_rows() {
+    let dir = tempfile::tempdir().unwrap();
+    let mut t = HeapTable::open_indexed(
+        dir.path().join("t.db"),
+        dir.path().join("t.idx"),
+        DEFAULT_PAGE_SIZE,
+        chusql_storage::config::DEFAULT_BTREE_ORDER,
+        DEFAULT_POOL_SIZE,
+    )
+    .unwrap();
+
+    for i in 1..=5 {
+        t.insert_row(&row(&[("id", json!(i)), ("name", json!(format!("u{}", i)))]))
+            .unwrap();
+    }
+
+    let deleted = t.delete_by_keys(&[2, 4, 99]).unwrap();
+    assert_eq!(deleted.len(), 2, "只有 2、4 真的删掉了");
+
+    let ids: Vec<i64> = t
+        .scan()
+        .unwrap()
+        .iter()
+        .map(|r| r["id"].as_i64().unwrap())
+        .collect();
+    assert_eq!(ids, vec![1, 3, 5], "剩下的行要保持原顺序");
+
+    assert!(t.get_by_key(2).unwrap().is_none(), "索引条目要跟着删");
+    assert!(t.get_by_key(4).unwrap().is_none());
+    assert!(t.get_by_key(3).unwrap().is_some());
+
+    // 删掉的位置可以再插回来
+    t.insert_row(&row(&[("id", json!(2)), ("name", json!("u2b"))]))
+        .unwrap();
+    assert_eq!(t.get_by_key(2).unwrap().unwrap()["name"], json!("u2b"));
+}
+
+/// 批量插入
+#[test]
+fn insert_rows_batch() {
+    let dir = tempfile::tempdir().unwrap();
+    let mut t = HeapTable::open_indexed(
+        dir.path().join("t.db"),
+        dir.path().join("t.idx"),
+        DEFAULT_PAGE_SIZE,
+        chusql_storage::config::DEFAULT_BTREE_ORDER,
+        DEFAULT_POOL_SIZE,
+    )
+    .unwrap();
+
+    let rows: Vec<Row> = (1..=20)
+        .map(|i| row(&[("id", json!(i)), ("name", json!(format!("u{}", i)))]))
+        .collect();
+    t.insert_rows(&rows).unwrap();
+
+    assert_eq!(t.scan().unwrap().len(), 20);
+    assert_eq!(t.get_by_key(20).unwrap().unwrap()["name"], json!("u20"));
+
+    // 批里出现重复键要报错（整批之前就查出来，不会插一半）
+    let dup = vec![
+        row(&[("id", json!(100))]),
+        row(&[("id", json!(100))]),
+    ];
+    assert!(t.insert_rows(&dup).is_err());
+}
+
+/// 第二列索引：建索引时要求唯一，建完之后插入/删除都跟着维护
+#[test]
+fn secondary_index_is_maintained() {
+    let dir = tempfile::tempdir().unwrap();
+    let mut t = HeapTable::open_indexed(
+        dir.path().join("t.db"),
+        dir.path().join("t.idx"),
+        DEFAULT_PAGE_SIZE,
+        chusql_storage::config::DEFAULT_BTREE_ORDER,
+        DEFAULT_POOL_SIZE,
+    )
+    .unwrap();
+
+    t.insert_rows(&[
+        row(&[("id", json!(1)), ("code", json!(7001))]),
+        row(&[("id", json!(2)), ("code", json!(7002))]),
+    ])
+    .unwrap();
+
+    assert!(!t.has_index("code"));
+    t.build_index(
+        "code",
+        &dir.path().join("t.code.idx"),
+        DEFAULT_PAGE_SIZE,
+        chusql_storage::config::DEFAULT_BTREE_ORDER,
+        DEFAULT_POOL_SIZE,
+    )
+    .unwrap();
+    assert!(t.has_index("code"));
+    assert_eq!(t.get_by_column_key("code", 7002).unwrap().unwrap()["id"], json!(2));
+
+    // 建索引之后新插入的行也进索引
+    t.insert_row(&row(&[("id", json!(3)), ("code", json!(7003))]))
+        .unwrap();
+    assert_eq!(t.get_by_column_key("code", 7003).unwrap().unwrap()["id"], json!(3));
+
+    // 删掉一行，索引条目跟着走
+    t.delete_by_keys(&[2]).unwrap();
+    assert!(t.get_by_column_key("code", 7002).unwrap().is_none());
+
+    // code 已经有索引，重复的 code 插不进去（索引列是唯一的）
+    assert!(t.insert_row(&row(&[("id", json!(4)), ("code", json!(7001))])).is_err());
+    let mut t2 = HeapTable::open(&dir.path().join("d.db"), DEFAULT_PAGE_SIZE, DEFAULT_POOL_SIZE).unwrap();
+    t2.insert_rows(&[
+        row(&[("id", json!(1)), ("age", json!(30))]),
+        row(&[("id", json!(2)), ("age", json!(30))]),
+    ])
+    .unwrap();
+    let err = t2.build_index(
+        "age",
+        &dir.path().join("d.age.idx"),
+        DEFAULT_PAGE_SIZE,
+        chusql_storage::config::DEFAULT_BTREE_ORDER,
+        DEFAULT_POOL_SIZE,
+    );
+    assert!(err.is_err(), "重复值不给建索引");
+    assert!(!t2.has_index("age"), "失败之后不留半成品");
+}
+
+/// 同一个 id 插两次要报错
+#[test]
+fn duplicate_key_is_rejected() {
+    let dir = tempfile::tempdir().unwrap();
+    let mut t = HeapTable::open_indexed(
+        dir.path().join("t.db"),
+        dir.path().join("t.idx"),
+        DEFAULT_PAGE_SIZE,
+        chusql_storage::config::DEFAULT_BTREE_ORDER,
+        DEFAULT_POOL_SIZE,
+    )
+    .unwrap();
+
+    t.insert_row(&row(&[("id", json!(1))])).unwrap();
+    let r = t.insert_row(&row(&[("id", json!(1))]));
+    assert!(r.is_err());
+    assert_eq!(t.scan().unwrap().len(), 1, "失败的那一行不应该进堆表");
+}
+
diff --git a/chusql-storage/tests/pipe_test.rs b/chusql-storage/tests/pipe_test.rs
index 23283ef..431c276 100644
--- a/chusql-storage/tests/pipe_test.rs
+++ b/chusql-storage/tests/pipe_test.rs
@@ -152,17 +152,17 @@ fn replace_all_replaces_rows() {
     assert!(!r.contains("Alice"), "old row should be gone: {}", r);
 }
 
-/// 带 key 插入后能按下标查
+/// 按 id 查（列名走默认值 `id`，老客户端不用改）
 #[test]
-fn insert_with_key_then_lookup() {
+fn insert_then_lookup_by_index() {
     let pipe = unique_pipe_name();
     let (_srv, _data) = start_server(&pipe);
     let mut c = connect(&pipe).unwrap();
 
     for (id, name) in [(1, "Alice"), (2, "Bob"), (3, "Carol")] {
         let req = format!(
-            r#"{{"method":"insert","table":"idx_users","row":{{"id":{},"name":"{}"}},"key":{}}}"#,
-            id, name, id
+            r#"{{"method":"insert","table":"idx_users","row":{{"id":{},"name":"{}"}}}}"#,
+            id, name
         );
         let r = send(&mut c, &req);
         assert!(r.contains(r#""status":"ok""#), "insert: {}", r);
@@ -175,16 +175,170 @@ fn insert_with_key_then_lookup() {
     assert!(r.contains(r#""rows":[]"#), "miss: {}", r);
 }
 
-/// 不带 key 不建索引
+/// 插入时索引由表自己维护：没给 key，id 也会进索引
 #[test]
-fn insert_without_key_does_not_index() {
+fn insert_indexes_the_id_column_automatically() {
     let pipe = unique_pipe_name();
     let (_srv, _data) = start_server(&pipe);
     let mut c = connect(&pipe).unwrap();
 
-    send(&mut c, r#"{"method":"insert","table":"nokey","row":{"id":1}}"#);
-    let r = send(&mut c, r#"{"method":"lookup_by_index","table":"nokey","key":1}"#);
-    assert!(r.contains(r#""rows":[]"#), "got: {}", r);
+    send(&mut c, r#"{"method":"insert","table":"auto_idx","row":{"id":7,"name":"Zoe"}}"#);
+    let r = send(
+        &mut c,
+        r#"{"method":"lookup_by_index","table":"auto_idx","column":"id","key":7}"#,
+    );
+    assert!(r.contains("Zoe"), "got: {}", r);
+}
+
+/// 同一个 id 插两次要报错（索引列是唯一的）
+#[test]
+fn duplicate_id_is_rejected() {
+    let pipe = unique_pipe_name();
+    let (_srv, _data) = start_server(&pipe);
+    let mut c = connect(&pipe).unwrap();
+
+    let req = r#"{"method":"insert","table":"dup_id","row":{"id":1,"name":"A"}}"#;
+    assert!(send(&mut c, req).contains(r#""status":"ok""#));
+
+    let r = send(&mut c, r#"{"method":"insert","table":"dup_id","row":{"id":1,"name":"B"}}"#);
+    assert!(r.contains(r#""status":"error""#), "got: {}", r);
+    assert!(r.contains("duplicate key"), "got: {}", r);
+}
+
+/// 批量插入一次全进
+#[test]
+fn insert_batch_writes_all_rows() {
+    let pipe = unique_pipe_name();
+    let (_srv, _data) = start_server(&pipe);
+    let mut c = connect(&pipe).unwrap();
+
+    let r = send(
+        &mut c,
+        r#"{"method":"insert_batch","table":"batch_t","rows":[{"id":1,"name":"A"},{"id":2,"name":"B"},{"id":3,"name":"C"}]}"#,
+    );
+    assert!(r.contains(r#""status":"ok""#), "batch: {}", r);
+
+    let r = send(&mut c, r#"{"method":"scan","table":"batch_t"}"#);
+    assert!(r.contains("A") && r.contains("B") && r.contains("C"), "scan: {}", r);
+
+    let r = send(&mut c, r#"{"method":"lookup_by_index","table":"batch_t","key":2}"#);
+    assert!(r.contains("B"), "index after batch: {}", r);
+}
+
+/// 行级删除：行没了、索引条目也没了、别人不受影响
+#[test]
+fn delete_keys_removes_row_and_index_entry() {
+    let pipe = unique_pipe_name();
+    let (_srv, _data) = start_server(&pipe);
+    let mut c = connect(&pipe).unwrap();
+
+    for (id, name) in [(1, "Alice"), (2, "Bob"), (3, "Carol")] {
+        let req = format!(
+            r#"{{"method":"insert","table":"del_t","row":{{"id":{},"name":"{}"}}}}"#,
+            id, name
+        );
+        send(&mut c, &req);
+    }
+
+    let r = send(&mut c, r#"{"method":"delete_keys","table":"del_t","keys":[2]}"#);
+    assert!(r.contains(r#""status":"ok""#), "delete: {}", r);
+
+    let r = send(&mut c, r#"{"method":"scan","table":"del_t"}"#);
+    assert!(!r.contains("Bob"), "row should be gone: {}", r);
+    assert!(r.contains("Alice") && r.contains("Carol"), "others stay: {}", r);
+
+    let r = send(&mut c, r#"{"method":"lookup_by_index","table":"del_t","key":2}"#);
+    assert!(r.contains(r#""rows":[]"#), "index entry should be gone: {}", r);
+
+    let r = send(&mut c, r#"{"method":"insert","table":"del_t","row":{"id":2,"name":"Bob2"}}"#);
+    assert!(r.contains(r#""status":"ok""#), "id 2 应该能再插进来: {}", r);
+}
+
+/// 给第二列建索引后能按那一列查
+#[test]
+fn create_index_on_secondary_column() {
+    let pipe = unique_pipe_name();
+    let (_srv, _data) = start_server(&pipe);
+    let mut c = connect(&pipe).unwrap();
+
+    for (id, code) in [(1, 5001), (2, 5002), (3, 5003)] {
+        let req = format!(
+            r#"{{"method":"insert","table":"sec_t","row":{{"id":{},"code":{}}}}}"#,
+            id, code
+        );
+        send(&mut c, &req);
+    }
+
+    // 没建之前：明确回 no_index，而不是回空结果
+    let r = send(&mut c, r#"{"method":"lookup_by_index","table":"sec_t","column":"code","key":5002}"#);
+    assert!(r.contains(r#""status":"no_index""#), "got: {}", r);
+
+    let r = send(&mut c, r#"{"method":"create_index","table":"sec_t","column":"code"}"#);
+    assert!(r.contains(r#""status":"ok""#), "create_index: {}", r);
+
+    let r = send(&mut c, r#"{"method":"lookup_by_index","table":"sec_t","column":"code","key":5002}"#);
+    assert!(r.contains(r#""id":2"#), "lookup by code: {}", r);
+
+    // 建完索引之后新插入的行也要进索引
+    send(&mut c, r#"{"method":"insert","table":"sec_t","row":{"id":4,"code":5004}}"#);
+    let r = send(&mut c, r#"{"method":"lookup_by_index","table":"sec_t","column":"code","key":5004}"#);
+    assert!(r.contains(r#""id":4"#), "lookup new row: {}", r);
+
+    // schema 里能看到这条索引
+    let r = send(&mut c, r#"{"method":"describe_table","table":"sec_t"}"#);
+    assert!(r.contains(r#""column":"code""#), "describe: {}", r);
+
+    // 删掉索引后回到 no_index
+    let r = send(&mut c, r#"{"method":"drop_index","table":"sec_t","column":"code"}"#);
+    assert!(r.contains(r#""status":"ok""#), "drop_index: {}", r);
+    let r = send(&mut c, r#"{"method":"lookup_by_index","table":"sec_t","column":"code","key":5002}"#);
+    assert!(r.contains(r#""status":"no_index""#), "after drop: {}", r);
+}
+
+/// 有重复值的列不给建索引（不然"走索引"和"全表扫"会给出不同答案）
+#[test]
+fn create_index_rejects_duplicate_values() {
+    let pipe = unique_pipe_name();
+    let (_srv, _data) = start_server(&pipe);
+    let mut c = connect(&pipe).unwrap();
+
+    send(&mut c, r#"{"method":"insert","table":"dup_t","row":{"id":1,"age":30}}"#);
+    send(&mut c, r#"{"method":"insert","table":"dup_t","row":{"id":2,"age":30}}"#);
+
+    let r = send(&mut c, r#"{"method":"create_index","table":"dup_t","column":"age"}"#);
+    assert!(r.contains(r#""status":"error""#), "got: {}", r);
+    assert!(r.contains("duplicate value"), "got: {}", r);
+
+    // 失败之后不留半成品：查这一列仍然是 no_index
+    let r = send(&mut c, r#"{"method":"lookup_by_index","table":"dup_t","column":"age","key":30}"#);
+    assert!(r.contains(r#""status":"no_index""#), "got: {}", r);
+}
+
+/// 数据字典里的统计：不同值个数
+#[test]
+fn stats_report_distinct_values() {
+    let pipe = unique_pipe_name();
+    let (_srv, _data) = start_server(&pipe);
+    let mut c = connect(&pipe).unwrap();
+
+    for (id, age) in [(1, 30), (2, 30), (3, 41)] {
+        let req = format!(
+            r#"{{"method":"insert","table":"stat_t","row":{{"id":{},"age":{}}}}}"#,
+            id, age
+        );
+        send(&mut c, &req);
+    }
+
+    let r = send(&mut c, r#"{"method":"describe_table","table":"stat_t"}"#);
+    assert!(r.contains(r#""row_count":3"#), "row_count: {}", r);
+    assert!(r.contains(r#""name":"age","distinct":2"#), "age 有 2 个不同值: {}", r);
+    assert!(r.contains(r#""name":"id","distinct":3"#), "id 有 3 个不同值: {}", r);
+
+    // 删掉一行，统计跟着掉
+    send(&mut c, r#"{"method":"delete_keys","table":"stat_t","keys":[1]}"#);
+    let r = send(&mut c, r#"{"method":"describe_table","table":"stat_t"}"#);
+    assert!(r.contains(r#""row_count":2"#), "after delete: {}", r);
+    assert!(r.contains(r#""name":"age","distinct":1"#), "after delete: {}", r);
 }
 
 /// 重开服务后索引仍在
diff --git a/chusql-storage/tests/wal_test.rs b/chusql-storage/tests/wal_test.rs
index d0feeb2..eccdb22 100644
--- a/chusql-storage/tests/wal_test.rs
+++ b/chusql-storage/tests/wal_test.rs
@@ -22,7 +22,6 @@ fn append_and_read_insert() {
     let op = WalOp::Insert {
         table: "users".into(),
         row: row(&[("id", json!(1)), ("name", json!("Alice"))]),
-        key: Some(1),
     };
     wal.append(&op).unwrap();
 
@@ -77,7 +76,6 @@ fn clear_truncates() {
     wal.append(&WalOp::Insert {
         table: "t".into(),
         row: row(&[("id", json!(1))]),
-        key: None,
     })
     .unwrap();
     assert!(wal.read().unwrap().is_some());
@@ -97,7 +95,6 @@ fn truncated_tail_is_ignored() {
     wal.append(&WalOp::Insert {
         table: "users".into(),
         row: row(&[("id", json!(1)), ("name", json!("Alice"))]),
-        key: Some(1),
     })
     .unwrap();
 
@@ -116,9 +113,9 @@ fn overwrite_on_second_append_is_visible() {
     wal.append(&WalOp::Insert {
         table: "t".into(),
         row: row(&[("id", json!(1))]),
-        key: None,
     })
     .unwrap();
     let first = wal.read().unwrap().unwrap();
     assert!(matches!(first, WalOp::Insert { .. }));
 }
+