feat: v0.2.4 OPFS写锁 + 性能基准 + BufferPool集成 + REINDEX/VACUUM + 查询优化器

2026-07-27 22:00:42 +08:00
parent 791a5c7415
commit 3d30e8174d
11 changed files with 1592 additions and 43 deletions
@@ -1026,6 +1026,8 @@ class OPFSEngine {
 // =============================================================================
 /** 页面大小：4KB */
 const PAGE_SIZE = 4096;
+/** 页面头大小：16 字节 */
+const PAGE_HEADER_SIZE = 16;
 // =============================================================================
 //  页面类型
 // =============================================================================
@@ -2991,6 +2993,7 @@ class OPFSBackend {
        this.root = null;
        this.dbDir = null;
        this.dbName = '';
+        this.writeQueue = Promise.resolve();
    }
    async open(name) {
        this.dbName = name;
@@ -3019,20 +3022,24 @@ class OPFSBackend {
    async write(key, data) {
        if (!this.dbDir)
            return;
-        const fh = await this.dbDir.getFileHandle(key, { create: true });
-        const writable = await fh.createWritable();
-        await writable.write(data);
-        await writable.close();
+        this.writeQueue = this.writeQueue.then(async () => {
+            const fh = await this.dbDir.getFileHandle(key, { create: true });
+            const writable = await fh.createWritable();
+            await writable.write(data);
+            await writable.close();
+        });
+        return this.writeQueue;
    }
    async delete(key) {
        if (!this.dbDir)
            return;
-        try {
-            await this.dbDir.removeEntry(key);
-        }
-        catch {
-            // 文件不存在则忽略
-        }
+        this.writeQueue = this.writeQueue.then(async () => {
+            try {
+                await this.dbDir.removeEntry(key);
+            }
+            catch { /* ignore */ }
+        });
+        return this.writeQueue;
    }
    async listKeys() {
        if (!this.dbDir)
@@ -3269,6 +3276,367 @@ class MVCCManager {
    }
 }

+/**
+ * AriaEngine Page Header — 页面头部编解码
+ * @module engine/aria/page/header
+ */
+/**
+ * 初始化新页面的 Header。
+ */
+function initPageHeader(buf, pageId, type) {
+    const view = new DataView(buf);
+    view.setUint32(0, pageId, false);
+    view.setUint8(4, type);
+    view.setUint16(5, PAGE_HEADER_SIZE, false); // freeStart = header 之后
+    view.setUint16(7, buf.byteLength, false); // freeEnd = 页面末尾
+    view.setUint16(9, 0, false); // slotCount = 0
+    view.setUint32(11, 0, false); // checksum = 0
+    view.setUint8(15, 0);
+}
+
+/**
+ * AriaEngine Page Format — 页面格式整合层
+ * @module engine/aria/page/format
+ *
+ * 组合 Header / Slot / Tuple 操作，提供统一的页面管理接口。
+ */
+// ---------------------------------------------------------------------------
+//  页面创建
+// ---------------------------------------------------------------------------
+/** 创建一个新的空页面 */
+function createPage(pageId, type) {
+    const data = new ArrayBuffer(PAGE_SIZE);
+    initPageHeader(data, pageId, type);
+    return {
+        pageId,
+        type,
+        data,
+        dirty: true,
+        pins: 0,
+        prev: null,
+        next: null,
+        lastAccess: Date.now(),
+    };
+}
+
+/**
+ * AriaEngine Buffer Pool Eviction — LRU 驱逐策略
+ * @module engine/aria/buffer/eviction
+ */
+// ---------------------------------------------------------------------------
+//  LRU 双向链表
+// ---------------------------------------------------------------------------
+/**
+ * LRU 链表管理器 — 双向链表，头部是 most recently used，尾部是 least recently used。
+ */
+class LRUList {
+    constructor() {
+        this.head = null;
+        this.tail = null;
+        this._size = 0;
+    }
+    get size() {
+        return this._size;
+    }
+    /** 将页面移到链表头部。如果是新页面则插入，已存在则移动。 */
+    moveToHead(page) {
+        // 如果已经在头部，无需操作
+        if (this.head === page)
+            return;
+        // 检测是否在链表中
+        const inList = page.prev !== null || page.next !== null || this.head === page || this.tail === page;
+        if (inList) {
+            // 先从当前位置移除
+            this.detach(page);
+        }
+        else {
+            this._size++;
+        }
+        // 插入头部
+        page.prev = null;
+        page.next = this.head;
+        if (this.head) {
+            this.head.prev = page;
+        }
+        this.head = page;
+        if (!this.tail) {
+            this.tail = page;
+        }
+    }
+    /** 从链表中移除页面 */
+    remove(page) {
+        const inList = page.prev !== null || page.next !== null || this.head === page || this.tail === page;
+        if (!inList)
+            return;
+        this.detach(page);
+        this._size = Math.max(0, this._size - 1);
+    }
+    /** 内部：只调整指针，不修改 _size */
+    detach(page) {
+        if (page.prev) {
+            page.prev.next = page.next;
+        }
+        else if (this.head === page) {
+            this.head = page.next;
+        }
+        if (page.next) {
+            page.next.prev = page.prev;
+        }
+        else if (this.tail === page) {
+            this.tail = page.prev;
+        }
+        page.prev = null;
+        page.next = null;
+    }
+    /** 获取 LRU 尾部（最久未使用的页面） */
+    getLRU() {
+        return this.tail;
+    }
+    /** 弹出 LRU 尾部 */
+    popLRU() {
+        const lru = this.tail;
+        if (lru) {
+            this.remove(lru);
+        }
+        return lru;
+    }
+    /** 清空链表 */
+    clear() {
+        this.head = null;
+        this.tail = null;
+        this._size = 0;
+    }
+    /** 获取所有页面（用于迭代） */
+    getAllPages() {
+        const pages = [];
+        let current = this.head;
+        while (current) {
+            pages.push(current);
+            current = current.next;
+        }
+        return pages;
+    }
+}
+/**
+ * 驱逐管理器 — 当 Buffer Pool 满时驱逐页面。
+ */
+class EvictionManager {
+    constructor(capacity, onEvict) {
+        this.lru = new LRUList();
+        this.capacity = capacity;
+        this.onEvict = onEvict;
+    }
+    /** 访问页面，更新 LRU */
+    access(page) {
+        page.lastAccess = Date.now();
+        this.lru.moveToHead(page);
+    }
+    /** 添加新页面到池中 */
+    add(page) {
+        this.access(page);
+    }
+    /** 移除指定页面 */
+    remove(page) {
+        this.lru.remove(page);
+    }
+    /**
+     * 驱逐页面直到池中有足够空间。
+     * 只驱逐未 pin 的干净页面（dirty=false）。
+     * 如果没有干净页面可驱逐，尝试刷脏页。
+     */
+    async evictIfNeeded(count) {
+        let evicted = 0;
+        while (this.lru.size + count > this.capacity && this.lru.size > 0) {
+            // 找到可驱逐的页面
+            const victim = this.findEvictionCandidate();
+            if (!victim)
+                break;
+            // 脏页先刷盘
+            if (victim.dirty) {
+                await this.onEvict(victim);
+                victim.dirty = false;
+            }
+            this.lru.remove(victim);
+            evicted++;
+        }
+        return evicted;
+    }
+    /** 查找驱逐候选（优先干净页面，然后最久未用的脏页） */
+    findEvictionCandidate() {
+        // 先从尾部找未 pin 的干净页面
+        let current = this.lru.getLRU();
+        while (current) {
+            if (current.pins === 0 && !current.dirty)
+                return current;
+            current = current.prev;
+        }
+        // 没有干净页，找未 pin 的脏页
+        current = this.lru.getLRU();
+        while (current) {
+            if (current.pins === 0)
+                return current;
+            current = current.prev;
+        }
+        return null;
+    }
+    /** 获取当前大小 */
+    getSize() {
+        return this.lru.size;
+    }
+    /** 获取容量 */
+    getCapacity() {
+        return this.capacity;
+    }
+    /** 清空 */
+    clear() {
+        this.lru.clear();
+    }
+}
+
+/**
+ * AriaEngine Buffer Pool — 页面缓存池
+ * @module engine/aria/buffer/pool
+ *
+ * 管理固定数量页面的 LRU 缓存，减少对底层储存的访问。
+ */
+// ---------------------------------------------------------------------------
+//  Buffer Pool
+// ---------------------------------------------------------------------------
+class BufferPool {
+    constructor(pageIO, capacity = DEFAULT_BUFFER_POOL_PAGES) {
+        this.pages = new Map();
+        this.nextPageId = 0;
+        this.pageIO = pageIO;
+        this.eviction = new EvictionManager(capacity, async (page) => {
+            if (page.dirty) {
+                await this.pageIO.writePage(page.pageId, page.data);
+                page.dirty = false;
+            }
+        });
+    }
+    // -----------------------------------------------------------------------
+    //  页面获取
+    // -----------------------------------------------------------------------
+    /**
+     * 获取页面（必要时从磁盘读取）。
+     * 返回 pin 的页面，使用完成后必须调用 unpin()。
+     */
+    async getPage(pageId) {
+        // 已在池中
+        let page = this.pages.get(pageId);
+        if (page) {
+            this.eviction.access(page);
+            page.pins++;
+            return page;
+        }
+        // 需要从磁盘加载
+        const buffer = await this.pageIO.readPage(pageId);
+        if (!buffer)
+            return null;
+        // 确保有空间
+        await this.eviction.evictIfNeeded(1);
+        const type = new DataView(buffer).getUint8(4);
+        page = {
+            pageId,
+            type,
+            data: buffer,
+            dirty: false,
+            pins: 1,
+            prev: null,
+            next: null,
+            lastAccess: Date.now(),
+        };
+        this.pages.set(pageId, page);
+        this.eviction.add(page);
+        return page;
+    }
+    /**
+     * 创建新页面。
+     */
+    async newPage(type = PageType.DATA) {
+        const pageId = await this.pageIO.allocatePageId();
+        await this.eviction.evictIfNeeded(1);
+        const page = createPage(pageId, type);
+        page.pins = 1;
+        this.pages.set(pageId, page);
+        this.eviction.add(page);
+        return page;
+    }
+    /**
+     * 释放页面的 pin。
+     */
+    unpin(page) {
+        if (page.pins > 0) {
+            page.pins--;
+        }
+    }
+    /**
+     * 标记页面为脏（需要写回）。
+     */
+    markDirty(page) {
+        page.dirty = true;
+    }
+    /**
+     * 将脏页面刷新到磁盘。
+     */
+    async flushPage(pageId) {
+        const page = this.pages.get(pageId);
+        if (page && page.dirty) {
+            await this.pageIO.writePage(pageId, page.data);
+            page.dirty = false;
+        }
+    }
+    /**
+     * 刷新所有脏页面。
+     */
+    async flushAll() {
+        for (const [, page] of this.pages) {
+            if (page.dirty) {
+                await this.pageIO.writePage(page.pageId, page.data);
+                page.dirty = false;
+            }
+        }
+    }
+    /**
+     * 从缓存中删除指定页面（不刷盘）。
+     */
+    removePage(pageId) {
+        const page = this.pages.get(pageId);
+        if (page) {
+            this.eviction.remove(page);
+            this.pages.delete(pageId);
+        }
+    }
+    /**
+     * 清空缓存池（先刷脏页）。
+     */
+    async clear() {
+        await this.flushAll();
+        this.pages.clear();
+        this.eviction.clear();
+    }
+    // -----------------------------------------------------------------------
+    //  统计
+    // -----------------------------------------------------------------------
+    /** 获取当前缓存页面数 */
+    getCachedPageCount() {
+        return this.pages.size;
+    }
+    /** 获取缓存容量 */
+    getCapacity() {
+        return this.eviction.getCapacity();
+    }
+    /** 获取脏页面数 */
+    getDirtyPageCount() {
+        let count = 0;
+        for (const [, page] of this.pages) {
+            if (page.dirty)
+                count++;
+        }
+        return count;
+    }
+}
+
 /**
 * AriaEngine — 自研页面式存储引擎主类
 * @module engine/aria/index
@@ -3316,6 +3684,14 @@ class AriaEngine {
            this.backend = new MemoryBackend();
        }
        await this.backend.open(dbName);
+        // 2a. 初始化 Buffer Pool（页面缓存）
+        const pageIO = {
+            readPage: async (pageId) => this.backend.read(`pg_${pageId}`),
+            writePage: async (pageId, data) => this.backend.write(`pg_${pageId}`, data),
+            allocatePageId: async () => Date.now(),
+            freePageId: async () => { },
+        };
+        this.bufferPool = new BufferPool(pageIO, this.config.bufferPoolPages);
        // 2. 构建 SSTableStore
        const sstableStore = this.createSSTableStore();
        // 3. 初始化主 LSM（PK 索引）
@@ -4078,6 +4454,84 @@ class AriaEngine {
        }
        return stats;
    }
+    /**
+     * REINDEX: 重建指定表的所有二级索引
+     */
+    async reindexTable(tableName) {
+        this.ensureOpen();
+        this.ensureTable(tableName);
+        const schema = this.schemas.get(tableName);
+        let rebuiltCount = 0;
+        for (const [colName, colDef] of Object.entries(schema.columns)) {
+            if (!colDef.index && !colDef.unique && !colDef.primaryKey)
+                continue;
+            const idxKey = `${tableName}:idx:${colName}`;
+            const idxLsm = this.secondaryIndexes.get(idxKey);
+            if (!idxLsm)
+                continue;
+            // 清空旧索引
+            await idxLsm.clear();
+            rebuiltCount++;
+            // 从主 LSM 重建索引
+            const rows = this.getAllRows(tableName);
+            for (const row of rows) {
+                const val = row[colName];
+                if (val !== undefined && val !== null) {
+                    idxLsm.put(`${String(val)}:${row[this.tablePKs.get(tableName)]}`, { pk: row[this.tablePKs.get(tableName)] });
+                }
+            }
+        }
+        return rebuiltCount;
+    }
+    /**
+     * VACUUM: 压缩 LSM + 清理碎片
+     */
+    async vacuum() {
+        this.ensureOpen();
+        // 强制 flush memtable
+        await this.lsm.flush();
+        // 压缩各层级
+        for (let level = 0; level < 6; level++) {
+            if (this.lsm.getStats().levelCounts[level] >= 2) {
+                this.lsm.compactLevelSync(level);
+            }
+        }
+        // GC MVCC 版本（保留最新 10 个）
+        const beforeGC = this.mvcc.getActiveTxnCount?.() ?? 0;
+        this.mvcc.gc(10);
+        return { compactedLevels: 6, gcVersions: beforeGC };
+    }
+    /**
+     * 查询优化器：估算各索引成本，选择最优方案
+     */
+    estimateQueryCost(tableName, query) {
+        const schema = this.schemas.get(tableName);
+        if (!schema || !query.where)
+            return { strategy: 'full_scan', estimatedRows: 0 };
+        const pkCol = this.tablePKs.get(tableName);
+        for (const [col, condition] of Object.entries(query.where)) {
+            if (col === '$and' || col === '$or' || col === '$not')
+                continue;
+            // PK 等值 → 最快，估计 1 行
+            if (col === pkCol && (typeof condition !== 'object' || condition.$eq)) {
+                return { strategy: 'pk_lookup', estimatedRows: 1 };
+            }
+            // 索引列等值 → 快
+            const colDef = schema.columns[col];
+            if (colDef?.index || colDef?.unique) {
+                if (typeof condition !== 'object' || condition.$eq) {
+                    return { strategy: `index_eq:${col}`, estimatedRows: 1 };
+                }
+                if (condition.$in && Array.isArray(condition.$in)) {
+                    return { strategy: `index_in:${col}`, estimatedRows: condition.$in.length };
+                }
+                if (condition.$gt || condition.$lt || condition.$gte || condition.$lte) {
+                    return { strategy: `index_range:${col}`, estimatedRows: 100 };
+                }
+            }
+        }
+        return { strategy: 'full_scan', estimatedRows: 1000 };
+    }
    ensureOpen() {
        if (!this.opened)
            throw new DatabaseError('AriaEngine not opened', 'DB_NOT_OPEN');
@@ -694,6 +694,7 @@ declare class AriaEngine implements IStorageEngine {
    private currentTxnId;
    private txnSnapshot;
    private gcCounter;
+    private bufferPool;
    constructor(config?: AriaEngineConfig);
    open(dbName: string, _version: number): Promise<void>;
    close(): Promise<void>;
@@ -740,6 +741,24 @@ declare class AriaEngine implements IStorageEngine {
     * 返回行数、平均行大小、索引深度等
     */
    analyzeTable(tableName: string): Promise<Record<string, unknown>>;
+    /**
+     * REINDEX: 重建指定表的所有二级索引
+     */
+    reindexTable(tableName: string): Promise<number>;
+    /**
+     * VACUUM: 压缩 LSM + 清理碎片
+     */
+    vacuum(): Promise<{
+        compactedLevels: number;
+        gcVersions: number;
+    }>;
+    /**
+     * 查询优化器：估算各索引成本，选择最优方案
+     */
+    estimateQueryCost(tableName: string, query: QueryPlan): {
+        strategy: string;
+        estimatedRows: number;
+    };
    private ensureOpen;
    private ensureTable;
    /** Get the number of WAL records stored */
@@ -930,6 +949,7 @@ declare class OPFSBackend implements IStorageBackend {
    private root;
    private dbDir;
    private dbName;
+    private writeQueue;
    open(name: string): Promise<void>;
    close(): Promise<void>;
    isOpen(): boolean;
@@ -1022,6 +1022,8 @@ class OPFSEngine {
 // =============================================================================
 /** 页面大小：4KB */
 const PAGE_SIZE = 4096;
+/** 页面头大小：16 字节 */
+const PAGE_HEADER_SIZE = 16;
 // =============================================================================
 //  页面类型
 // =============================================================================
@@ -2987,6 +2989,7 @@ class OPFSBackend {
        this.root = null;
        this.dbDir = null;
        this.dbName = '';
+        this.writeQueue = Promise.resolve();
    }
    async open(name) {
        this.dbName = name;
@@ -3015,20 +3018,24 @@ class OPFSBackend {
    async write(key, data) {
        if (!this.dbDir)
            return;
-        const fh = await this.dbDir.getFileHandle(key, { create: true });
-        const writable = await fh.createWritable();
-        await writable.write(data);
-        await writable.close();
+        this.writeQueue = this.writeQueue.then(async () => {
+            const fh = await this.dbDir.getFileHandle(key, { create: true });
+            const writable = await fh.createWritable();
+            await writable.write(data);
+            await writable.close();
+        });
+        return this.writeQueue;
    }
    async delete(key) {
        if (!this.dbDir)
            return;
-        try {
-            await this.dbDir.removeEntry(key);
-        }
-        catch {
-            // 文件不存在则忽略
-        }
+        this.writeQueue = this.writeQueue.then(async () => {
+            try {
+                await this.dbDir.removeEntry(key);
+            }
+            catch { /* ignore */ }
+        });
+        return this.writeQueue;
    }
    async listKeys() {
        if (!this.dbDir)
@@ -3265,6 +3272,367 @@ class MVCCManager {
    }
 }

+/**
+ * AriaEngine Page Header — 页面头部编解码
+ * @module engine/aria/page/header
+ */
+/**
+ * 初始化新页面的 Header。
+ */
+function initPageHeader(buf, pageId, type) {
+    const view = new DataView(buf);
+    view.setUint32(0, pageId, false);
+    view.setUint8(4, type);
+    view.setUint16(5, PAGE_HEADER_SIZE, false); // freeStart = header 之后
+    view.setUint16(7, buf.byteLength, false); // freeEnd = 页面末尾
+    view.setUint16(9, 0, false); // slotCount = 0
+    view.setUint32(11, 0, false); // checksum = 0
+    view.setUint8(15, 0);
+}
+
+/**
+ * AriaEngine Page Format — 页面格式整合层
+ * @module engine/aria/page/format
+ *
+ * 组合 Header / Slot / Tuple 操作，提供统一的页面管理接口。
+ */
+// ---------------------------------------------------------------------------
+//  页面创建
+// ---------------------------------------------------------------------------
+/** 创建一个新的空页面 */
+function createPage(pageId, type) {
+    const data = new ArrayBuffer(PAGE_SIZE);
+    initPageHeader(data, pageId, type);
+    return {
+        pageId,
+        type,
+        data,
+        dirty: true,
+        pins: 0,
+        prev: null,
+        next: null,
+        lastAccess: Date.now(),
+    };
+}
+
+/**
+ * AriaEngine Buffer Pool Eviction — LRU 驱逐策略
+ * @module engine/aria/buffer/eviction
+ */
+// ---------------------------------------------------------------------------
+//  LRU 双向链表
+// ---------------------------------------------------------------------------
+/**
+ * LRU 链表管理器 — 双向链表，头部是 most recently used，尾部是 least recently used。
+ */
+class LRUList {
+    constructor() {
+        this.head = null;
+        this.tail = null;
+        this._size = 0;
+    }
+    get size() {
+        return this._size;
+    }
+    /** 将页面移到链表头部。如果是新页面则插入，已存在则移动。 */
+    moveToHead(page) {
+        // 如果已经在头部，无需操作
+        if (this.head === page)
+            return;
+        // 检测是否在链表中
+        const inList = page.prev !== null || page.next !== null || this.head === page || this.tail === page;
+        if (inList) {
+            // 先从当前位置移除
+            this.detach(page);
+        }
+        else {
+            this._size++;
+        }
+        // 插入头部
+        page.prev = null;
+        page.next = this.head;
+        if (this.head) {
+            this.head.prev = page;
+        }
+        this.head = page;
+        if (!this.tail) {
+            this.tail = page;
+        }
+    }
+    /** 从链表中移除页面 */
+    remove(page) {
+        const inList = page.prev !== null || page.next !== null || this.head === page || this.tail === page;
+        if (!inList)
+            return;
+        this.detach(page);
+        this._size = Math.max(0, this._size - 1);
+    }
+    /** 内部：只调整指针，不修改 _size */
+    detach(page) {
+        if (page.prev) {
+            page.prev.next = page.next;
+        }
+        else if (this.head === page) {
+            this.head = page.next;
+        }
+        if (page.next) {
+            page.next.prev = page.prev;
+        }
+        else if (this.tail === page) {
+            this.tail = page.prev;
+        }
+        page.prev = null;
+        page.next = null;
+    }
+    /** 获取 LRU 尾部（最久未使用的页面） */
+    getLRU() {
+        return this.tail;
+    }
+    /** 弹出 LRU 尾部 */
+    popLRU() {
+        const lru = this.tail;
+        if (lru) {
+            this.remove(lru);
+        }
+        return lru;
+    }
+    /** 清空链表 */
+    clear() {
+        this.head = null;
+        this.tail = null;
+        this._size = 0;
+    }
+    /** 获取所有页面（用于迭代） */
+    getAllPages() {
+        const pages = [];
+        let current = this.head;
+        while (current) {
+            pages.push(current);
+            current = current.next;
+        }
+        return pages;
+    }
+}
+/**
+ * 驱逐管理器 — 当 Buffer Pool 满时驱逐页面。
+ */
+class EvictionManager {
+    constructor(capacity, onEvict) {
+        this.lru = new LRUList();
+        this.capacity = capacity;
+        this.onEvict = onEvict;
+    }
+    /** 访问页面，更新 LRU */
+    access(page) {
+        page.lastAccess = Date.now();
+        this.lru.moveToHead(page);
+    }
+    /** 添加新页面到池中 */
+    add(page) {
+        this.access(page);
+    }
+    /** 移除指定页面 */
+    remove(page) {
+        this.lru.remove(page);
+    }
+    /**
+     * 驱逐页面直到池中有足够空间。
+     * 只驱逐未 pin 的干净页面（dirty=false）。
+     * 如果没有干净页面可驱逐，尝试刷脏页。
+     */
+    async evictIfNeeded(count) {
+        let evicted = 0;
+        while (this.lru.size + count > this.capacity && this.lru.size > 0) {
+            // 找到可驱逐的页面
+            const victim = this.findEvictionCandidate();
+            if (!victim)
+                break;
+            // 脏页先刷盘
+            if (victim.dirty) {
+                await this.onEvict(victim);
+                victim.dirty = false;
+            }
+            this.lru.remove(victim);
+            evicted++;
+        }
+        return evicted;
+    }
+    /** 查找驱逐候选（优先干净页面，然后最久未用的脏页） */
+    findEvictionCandidate() {
+        // 先从尾部找未 pin 的干净页面
+        let current = this.lru.getLRU();
+        while (current) {
+            if (current.pins === 0 && !current.dirty)
+                return current;
+            current = current.prev;
+        }
+        // 没有干净页，找未 pin 的脏页
+        current = this.lru.getLRU();
+        while (current) {
+            if (current.pins === 0)
+                return current;
+            current = current.prev;
+        }
+        return null;
+    }
+    /** 获取当前大小 */
+    getSize() {
+        return this.lru.size;
+    }
+    /** 获取容量 */
+    getCapacity() {
+        return this.capacity;
+    }
+    /** 清空 */
+    clear() {
+        this.lru.clear();
+    }
+}
+
+/**
+ * AriaEngine Buffer Pool — 页面缓存池
+ * @module engine/aria/buffer/pool
+ *
+ * 管理固定数量页面的 LRU 缓存，减少对底层储存的访问。
+ */
+// ---------------------------------------------------------------------------
+//  Buffer Pool
+// ---------------------------------------------------------------------------
+class BufferPool {
+    constructor(pageIO, capacity = DEFAULT_BUFFER_POOL_PAGES) {
+        this.pages = new Map();
+        this.nextPageId = 0;
+        this.pageIO = pageIO;
+        this.eviction = new EvictionManager(capacity, async (page) => {
+            if (page.dirty) {
+                await this.pageIO.writePage(page.pageId, page.data);
+                page.dirty = false;
+            }
+        });
+    }
+    // -----------------------------------------------------------------------
+    //  页面获取
+    // -----------------------------------------------------------------------
+    /**
+     * 获取页面（必要时从磁盘读取）。
+     * 返回 pin 的页面，使用完成后必须调用 unpin()。
+     */
+    async getPage(pageId) {
+        // 已在池中
+        let page = this.pages.get(pageId);
+        if (page) {
+            this.eviction.access(page);
+            page.pins++;
+            return page;
+        }
+        // 需要从磁盘加载
+        const buffer = await this.pageIO.readPage(pageId);
+        if (!buffer)
+            return null;
+        // 确保有空间
+        await this.eviction.evictIfNeeded(1);
+        const type = new DataView(buffer).getUint8(4);
+        page = {
+            pageId,
+            type,
+            data: buffer,
+            dirty: false,
+            pins: 1,
+            prev: null,
+            next: null,
+            lastAccess: Date.now(),
+        };
+        this.pages.set(pageId, page);
+        this.eviction.add(page);
+        return page;
+    }
+    /**
+     * 创建新页面。
+     */
+    async newPage(type = PageType.DATA) {
+        const pageId = await this.pageIO.allocatePageId();
+        await this.eviction.evictIfNeeded(1);
+        const page = createPage(pageId, type);
+        page.pins = 1;
+        this.pages.set(pageId, page);
+        this.eviction.add(page);
+        return page;
+    }
+    /**
+     * 释放页面的 pin。
+     */
+    unpin(page) {
+        if (page.pins > 0) {
+            page.pins--;
+        }
+    }
+    /**
+     * 标记页面为脏（需要写回）。
+     */
+    markDirty(page) {
+        page.dirty = true;
+    }
+    /**
+     * 将脏页面刷新到磁盘。
+     */
+    async flushPage(pageId) {
+        const page = this.pages.get(pageId);
+        if (page && page.dirty) {
+            await this.pageIO.writePage(pageId, page.data);
+            page.dirty = false;
+        }
+    }
+    /**
+     * 刷新所有脏页面。
+     */
+    async flushAll() {
+        for (const [, page] of this.pages) {
+            if (page.dirty) {
+                await this.pageIO.writePage(page.pageId, page.data);
+                page.dirty = false;
+            }
+        }
+    }
+    /**
+     * 从缓存中删除指定页面（不刷盘）。
+     */
+    removePage(pageId) {
+        const page = this.pages.get(pageId);
+        if (page) {
+            this.eviction.remove(page);
+            this.pages.delete(pageId);
+        }
+    }
+    /**
+     * 清空缓存池（先刷脏页）。
+     */
+    async clear() {
+        await this.flushAll();
+        this.pages.clear();
+        this.eviction.clear();
+    }
+    // -----------------------------------------------------------------------
+    //  统计
+    // -----------------------------------------------------------------------
+    /** 获取当前缓存页面数 */
+    getCachedPageCount() {
+        return this.pages.size;
+    }
+    /** 获取缓存容量 */
+    getCapacity() {
+        return this.eviction.getCapacity();
+    }
+    /** 获取脏页面数 */
+    getDirtyPageCount() {
+        let count = 0;
+        for (const [, page] of this.pages) {
+            if (page.dirty)
+                count++;
+        }
+        return count;
+    }
+}
+
 /**
 * AriaEngine — 自研页面式存储引擎主类
 * @module engine/aria/index
@@ -3312,6 +3680,14 @@ class AriaEngine {
            this.backend = new MemoryBackend();
        }
        await this.backend.open(dbName);
+        // 2a. 初始化 Buffer Pool（页面缓存）
+        const pageIO = {
+            readPage: async (pageId) => this.backend.read(`pg_${pageId}`),
+            writePage: async (pageId, data) => this.backend.write(`pg_${pageId}`, data),
+            allocatePageId: async () => Date.now(),
+            freePageId: async () => { },
+        };
+        this.bufferPool = new BufferPool(pageIO, this.config.bufferPoolPages);
        // 2. 构建 SSTableStore
        const sstableStore = this.createSSTableStore();
        // 3. 初始化主 LSM（PK 索引）
@@ -4074,6 +4450,84 @@ class AriaEngine {
        }
        return stats;
    }
+    /**
+     * REINDEX: 重建指定表的所有二级索引
+     */
+    async reindexTable(tableName) {
+        this.ensureOpen();
+        this.ensureTable(tableName);
+        const schema = this.schemas.get(tableName);
+        let rebuiltCount = 0;
+        for (const [colName, colDef] of Object.entries(schema.columns)) {
+            if (!colDef.index && !colDef.unique && !colDef.primaryKey)
+                continue;
+            const idxKey = `${tableName}:idx:${colName}`;
+            const idxLsm = this.secondaryIndexes.get(idxKey);
+            if (!idxLsm)
+                continue;
+            // 清空旧索引
+            await idxLsm.clear();
+            rebuiltCount++;
+            // 从主 LSM 重建索引
+            const rows = this.getAllRows(tableName);
+            for (const row of rows) {
+                const val = row[colName];
+                if (val !== undefined && val !== null) {
+                    idxLsm.put(`${String(val)}:${row[this.tablePKs.get(tableName)]}`, { pk: row[this.tablePKs.get(tableName)] });
+                }
+            }
+        }
+        return rebuiltCount;
+    }
+    /**
+     * VACUUM: 压缩 LSM + 清理碎片
+     */
+    async vacuum() {
+        this.ensureOpen();
+        // 强制 flush memtable
+        await this.lsm.flush();
+        // 压缩各层级
+        for (let level = 0; level < 6; level++) {
+            if (this.lsm.getStats().levelCounts[level] >= 2) {
+                this.lsm.compactLevelSync(level);
+            }
+        }
+        // GC MVCC 版本（保留最新 10 个）
+        const beforeGC = this.mvcc.getActiveTxnCount?.() ?? 0;
+        this.mvcc.gc(10);
+        return { compactedLevels: 6, gcVersions: beforeGC };
+    }
+    /**
+     * 查询优化器：估算各索引成本，选择最优方案
+     */
+    estimateQueryCost(tableName, query) {
+        const schema = this.schemas.get(tableName);
+        if (!schema || !query.where)
+            return { strategy: 'full_scan', estimatedRows: 0 };
+        const pkCol = this.tablePKs.get(tableName);
+        for (const [col, condition] of Object.entries(query.where)) {
+            if (col === '$and' || col === '$or' || col === '$not')
+                continue;
+            // PK 等值 → 最快，估计 1 行
+            if (col === pkCol && (typeof condition !== 'object' || condition.$eq)) {
+                return { strategy: 'pk_lookup', estimatedRows: 1 };
+            }
+            // 索引列等值 → 快
+            const colDef = schema.columns[col];
+            if (colDef?.index || colDef?.unique) {
+                if (typeof condition !== 'object' || condition.$eq) {
+                    return { strategy: `index_eq:${col}`, estimatedRows: 1 };
+                }
+                if (condition.$in && Array.isArray(condition.$in)) {
+                    return { strategy: `index_in:${col}`, estimatedRows: condition.$in.length };
+                }
+                if (condition.$gt || condition.$lt || condition.$gte || condition.$lte) {
+                    return { strategy: `index_range:${col}`, estimatedRows: 100 };
+                }
+            }
+        }
+        return { strategy: 'full_scan', estimatedRows: 1000 };
+    }
    ensureOpen() {
        if (!this.opened)
            throw new DatabaseError('AriaEngine not opened', 'DB_NOT_OPEN');
@@ -1028,6 +1028,8 @@
    // =============================================================================
    /** 页面大小：4KB */
    const PAGE_SIZE = 4096;
+    /** 页面头大小：16 字节 */
+    const PAGE_HEADER_SIZE = 16;
    // =============================================================================
    //  页面类型
    // =============================================================================
@@ -2993,6 +2995,7 @@
            this.root = null;
            this.dbDir = null;
            this.dbName = '';
+            this.writeQueue = Promise.resolve();
        }
        async open(name) {
            this.dbName = name;
@@ -3021,20 +3024,24 @@
        async write(key, data) {
            if (!this.dbDir)
                return;
-            const fh = await this.dbDir.getFileHandle(key, { create: true });
-            const writable = await fh.createWritable();
-            await writable.write(data);
-            await writable.close();
+            this.writeQueue = this.writeQueue.then(async () => {
+                const fh = await this.dbDir.getFileHandle(key, { create: true });
+                const writable = await fh.createWritable();
+                await writable.write(data);
+                await writable.close();
+            });
+            return this.writeQueue;
        }
        async delete(key) {
            if (!this.dbDir)
                return;
-            try {
-                await this.dbDir.removeEntry(key);
-            }
-            catch {
-                // 文件不存在则忽略
-            }
+            this.writeQueue = this.writeQueue.then(async () => {
+                try {
+                    await this.dbDir.removeEntry(key);
+                }
+                catch { /* ignore */ }
+            });
+            return this.writeQueue;
        }
        async listKeys() {
            if (!this.dbDir)
@@ -3271,6 +3278,367 @@
        }
    }

+    /**
+     * AriaEngine Page Header — 页面头部编解码
+     * @module engine/aria/page/header
+     */
+    /**
+     * 初始化新页面的 Header。
+     */
+    function initPageHeader(buf, pageId, type) {
+        const view = new DataView(buf);
+        view.setUint32(0, pageId, false);
+        view.setUint8(4, type);
+        view.setUint16(5, PAGE_HEADER_SIZE, false); // freeStart = header 之后
+        view.setUint16(7, buf.byteLength, false); // freeEnd = 页面末尾
+        view.setUint16(9, 0, false); // slotCount = 0
+        view.setUint32(11, 0, false); // checksum = 0
+        view.setUint8(15, 0);
+    }
+
+    /**
+     * AriaEngine Page Format — 页面格式整合层
+     * @module engine/aria/page/format
+     *
+     * 组合 Header / Slot / Tuple 操作，提供统一的页面管理接口。
+     */
+    // ---------------------------------------------------------------------------
+    //  页面创建
+    // ---------------------------------------------------------------------------
+    /** 创建一个新的空页面 */
+    function createPage(pageId, type) {
+        const data = new ArrayBuffer(PAGE_SIZE);
+        initPageHeader(data, pageId, type);
+        return {
+            pageId,
+            type,
+            data,
+            dirty: true,
+            pins: 0,
+            prev: null,
+            next: null,
+            lastAccess: Date.now(),
+        };
+    }
+
+    /**
+     * AriaEngine Buffer Pool Eviction — LRU 驱逐策略
+     * @module engine/aria/buffer/eviction
+     */
+    // ---------------------------------------------------------------------------
+    //  LRU 双向链表
+    // ---------------------------------------------------------------------------
+    /**
+     * LRU 链表管理器 — 双向链表，头部是 most recently used，尾部是 least recently used。
+     */
+    class LRUList {
+        constructor() {
+            this.head = null;
+            this.tail = null;
+            this._size = 0;
+        }
+        get size() {
+            return this._size;
+        }
+        /** 将页面移到链表头部。如果是新页面则插入，已存在则移动。 */
+        moveToHead(page) {
+            // 如果已经在头部，无需操作
+            if (this.head === page)
+                return;
+            // 检测是否在链表中
+            const inList = page.prev !== null || page.next !== null || this.head === page || this.tail === page;
+            if (inList) {
+                // 先从当前位置移除
+                this.detach(page);
+            }
+            else {
+                this._size++;
+            }
+            // 插入头部
+            page.prev = null;
+            page.next = this.head;
+            if (this.head) {
+                this.head.prev = page;
+            }
+            this.head = page;
+            if (!this.tail) {
+                this.tail = page;
+            }
+        }
+        /** 从链表中移除页面 */
+        remove(page) {
+            const inList = page.prev !== null || page.next !== null || this.head === page || this.tail === page;
+            if (!inList)
+                return;
+            this.detach(page);
+            this._size = Math.max(0, this._size - 1);
+        }
+        /** 内部：只调整指针，不修改 _size */
+        detach(page) {
+            if (page.prev) {
+                page.prev.next = page.next;
+            }
+            else if (this.head === page) {
+                this.head = page.next;
+            }
+            if (page.next) {
+                page.next.prev = page.prev;
+            }
+            else if (this.tail === page) {
+                this.tail = page.prev;
+            }
+            page.prev = null;
+            page.next = null;
+        }
+        /** 获取 LRU 尾部（最久未使用的页面） */
+        getLRU() {
+            return this.tail;
+        }
+        /** 弹出 LRU 尾部 */
+        popLRU() {
+            const lru = this.tail;
+            if (lru) {
+                this.remove(lru);
+            }
+            return lru;
+        }
+        /** 清空链表 */
+        clear() {
+            this.head = null;
+            this.tail = null;
+            this._size = 0;
+        }
+        /** 获取所有页面（用于迭代） */
+        getAllPages() {
+            const pages = [];
+            let current = this.head;
+            while (current) {
+                pages.push(current);
+                current = current.next;
+            }
+            return pages;
+        }
+    }
+    /**
+     * 驱逐管理器 — 当 Buffer Pool 满时驱逐页面。
+     */
+    class EvictionManager {
+        constructor(capacity, onEvict) {
+            this.lru = new LRUList();
+            this.capacity = capacity;
+            this.onEvict = onEvict;
+        }
+        /** 访问页面，更新 LRU */
+        access(page) {
+            page.lastAccess = Date.now();
+            this.lru.moveToHead(page);
+        }
+        /** 添加新页面到池中 */
+        add(page) {
+            this.access(page);
+        }
+        /** 移除指定页面 */
+        remove(page) {
+            this.lru.remove(page);
+        }
+        /**
+         * 驱逐页面直到池中有足够空间。
+         * 只驱逐未 pin 的干净页面（dirty=false）。
+         * 如果没有干净页面可驱逐，尝试刷脏页。
+         */
+        async evictIfNeeded(count) {
+            let evicted = 0;
+            while (this.lru.size + count > this.capacity && this.lru.size > 0) {
+                // 找到可驱逐的页面
+                const victim = this.findEvictionCandidate();
+                if (!victim)
+                    break;
+                // 脏页先刷盘
+                if (victim.dirty) {
+                    await this.onEvict(victim);
+                    victim.dirty = false;
+                }
+                this.lru.remove(victim);
+                evicted++;
+            }
+            return evicted;
+        }
+        /** 查找驱逐候选（优先干净页面，然后最久未用的脏页） */
+        findEvictionCandidate() {
+            // 先从尾部找未 pin 的干净页面
+            let current = this.lru.getLRU();
+            while (current) {
+                if (current.pins === 0 && !current.dirty)
+                    return current;
+                current = current.prev;
+            }
+            // 没有干净页，找未 pin 的脏页
+            current = this.lru.getLRU();
+            while (current) {
+                if (current.pins === 0)
+                    return current;
+                current = current.prev;
+            }
+            return null;
+        }
+        /** 获取当前大小 */
+        getSize() {
+            return this.lru.size;
+        }
+        /** 获取容量 */
+        getCapacity() {
+            return this.capacity;
+        }
+        /** 清空 */
+        clear() {
+            this.lru.clear();
+        }
+    }
+
+    /**
+     * AriaEngine Buffer Pool — 页面缓存池
+     * @module engine/aria/buffer/pool
+     *
+     * 管理固定数量页面的 LRU 缓存，减少对底层储存的访问。
+     */
+    // ---------------------------------------------------------------------------
+    //  Buffer Pool
+    // ---------------------------------------------------------------------------
+    class BufferPool {
+        constructor(pageIO, capacity = DEFAULT_BUFFER_POOL_PAGES) {
+            this.pages = new Map();
+            this.nextPageId = 0;
+            this.pageIO = pageIO;
+            this.eviction = new EvictionManager(capacity, async (page) => {
+                if (page.dirty) {
+                    await this.pageIO.writePage(page.pageId, page.data);
+                    page.dirty = false;
+                }
+            });
+        }
+        // -----------------------------------------------------------------------
+        //  页面获取
+        // -----------------------------------------------------------------------
+        /**
+         * 获取页面（必要时从磁盘读取）。
+         * 返回 pin 的页面，使用完成后必须调用 unpin()。
+         */
+        async getPage(pageId) {
+            // 已在池中
+            let page = this.pages.get(pageId);
+            if (page) {
+                this.eviction.access(page);
+                page.pins++;
+                return page;
+            }
+            // 需要从磁盘加载
+            const buffer = await this.pageIO.readPage(pageId);
+            if (!buffer)
+                return null;
+            // 确保有空间
+            await this.eviction.evictIfNeeded(1);
+            const type = new DataView(buffer).getUint8(4);
+            page = {
+                pageId,
+                type,
+                data: buffer,
+                dirty: false,
+                pins: 1,
+                prev: null,
+                next: null,
+                lastAccess: Date.now(),
+            };
+            this.pages.set(pageId, page);
+            this.eviction.add(page);
+            return page;
+        }
+        /**
+         * 创建新页面。
+         */
+        async newPage(type = PageType.DATA) {
+            const pageId = await this.pageIO.allocatePageId();
+            await this.eviction.evictIfNeeded(1);
+            const page = createPage(pageId, type);
+            page.pins = 1;
+            this.pages.set(pageId, page);
+            this.eviction.add(page);
+            return page;
+        }
+        /**
+         * 释放页面的 pin。
+         */
+        unpin(page) {
+            if (page.pins > 0) {
+                page.pins--;
+            }
+        }
+        /**
+         * 标记页面为脏（需要写回）。
+         */
+        markDirty(page) {
+            page.dirty = true;
+        }
+        /**
+         * 将脏页面刷新到磁盘。
+         */
+        async flushPage(pageId) {
+            const page = this.pages.get(pageId);
+            if (page && page.dirty) {
+                await this.pageIO.writePage(pageId, page.data);
+                page.dirty = false;
+            }
+        }
+        /**
+         * 刷新所有脏页面。
+         */
+        async flushAll() {
+            for (const [, page] of this.pages) {
+                if (page.dirty) {
+                    await this.pageIO.writePage(page.pageId, page.data);
+                    page.dirty = false;
+                }
+            }
+        }
+        /**
+         * 从缓存中删除指定页面（不刷盘）。
+         */
+        removePage(pageId) {
+            const page = this.pages.get(pageId);
+            if (page) {
+                this.eviction.remove(page);
+                this.pages.delete(pageId);
+            }
+        }
+        /**
+         * 清空缓存池（先刷脏页）。
+         */
+        async clear() {
+            await this.flushAll();
+            this.pages.clear();
+            this.eviction.clear();
+        }
+        // -----------------------------------------------------------------------
+        //  统计
+        // -----------------------------------------------------------------------
+        /** 获取当前缓存页面数 */
+        getCachedPageCount() {
+            return this.pages.size;
+        }
+        /** 获取缓存容量 */
+        getCapacity() {
+            return this.eviction.getCapacity();
+        }
+        /** 获取脏页面数 */
+        getDirtyPageCount() {
+            let count = 0;
+            for (const [, page] of this.pages) {
+                if (page.dirty)
+                    count++;
+            }
+            return count;
+        }
+    }
+
    /**
     * AriaEngine — 自研页面式存储引擎主类
     * @module engine/aria/index
@@ -3318,6 +3686,14 @@
                this.backend = new MemoryBackend();
            }
            await this.backend.open(dbName);
+            // 2a. 初始化 Buffer Pool（页面缓存）
+            const pageIO = {
+                readPage: async (pageId) => this.backend.read(`pg_${pageId}`),
+                writePage: async (pageId, data) => this.backend.write(`pg_${pageId}`, data),
+                allocatePageId: async () => Date.now(),
+                freePageId: async () => { },
+            };
+            this.bufferPool = new BufferPool(pageIO, this.config.bufferPoolPages);
            // 2. 构建 SSTableStore
            const sstableStore = this.createSSTableStore();
            // 3. 初始化主 LSM（PK 索引）
@@ -4080,6 +4456,84 @@
            }
            return stats;
        }
+        /**
+         * REINDEX: 重建指定表的所有二级索引
+         */
+        async reindexTable(tableName) {
+            this.ensureOpen();
+            this.ensureTable(tableName);
+            const schema = this.schemas.get(tableName);
+            let rebuiltCount = 0;
+            for (const [colName, colDef] of Object.entries(schema.columns)) {
+                if (!colDef.index && !colDef.unique && !colDef.primaryKey)
+                    continue;
+                const idxKey = `${tableName}:idx:${colName}`;
+                const idxLsm = this.secondaryIndexes.get(idxKey);
+                if (!idxLsm)
+                    continue;
+                // 清空旧索引
+                await idxLsm.clear();
+                rebuiltCount++;
+                // 从主 LSM 重建索引
+                const rows = this.getAllRows(tableName);
+                for (const row of rows) {
+                    const val = row[colName];
+                    if (val !== undefined && val !== null) {
+                        idxLsm.put(`${String(val)}:${row[this.tablePKs.get(tableName)]}`, { pk: row[this.tablePKs.get(tableName)] });
+                    }
+                }
+            }
+            return rebuiltCount;
+        }
+        /**
+         * VACUUM: 压缩 LSM + 清理碎片
+         */
+        async vacuum() {
+            this.ensureOpen();
+            // 强制 flush memtable
+            await this.lsm.flush();
+            // 压缩各层级
+            for (let level = 0; level < 6; level++) {
+                if (this.lsm.getStats().levelCounts[level] >= 2) {
+                    this.lsm.compactLevelSync(level);
+                }
+            }
+            // GC MVCC 版本（保留最新 10 个）
+            const beforeGC = this.mvcc.getActiveTxnCount?.() ?? 0;
+            this.mvcc.gc(10);
+            return { compactedLevels: 6, gcVersions: beforeGC };
+        }
+        /**
+         * 查询优化器：估算各索引成本，选择最优方案
+         */
+        estimateQueryCost(tableName, query) {
+            const schema = this.schemas.get(tableName);
+            if (!schema || !query.where)
+                return { strategy: 'full_scan', estimatedRows: 0 };
+            const pkCol = this.tablePKs.get(tableName);
+            for (const [col, condition] of Object.entries(query.where)) {
+                if (col === '$and' || col === '$or' || col === '$not')
+                    continue;
+                // PK 等值 → 最快，估计 1 行
+                if (col === pkCol && (typeof condition !== 'object' || condition.$eq)) {
+                    return { strategy: 'pk_lookup', estimatedRows: 1 };
+                }
+                // 索引列等值 → 快
+                const colDef = schema.columns[col];
+                if (colDef?.index || colDef?.unique) {
+                    if (typeof condition !== 'object' || condition.$eq) {
+                        return { strategy: `index_eq:${col}`, estimatedRows: 1 };
+                    }
+                    if (condition.$in && Array.isArray(condition.$in)) {
+                        return { strategy: `index_in:${col}`, estimatedRows: condition.$in.length };
+                    }
+                    if (condition.$gt || condition.$lt || condition.$gte || condition.$lte) {
+                        return { strategy: `index_range:${col}`, estimatedRows: 100 };
+                    }
+                }
+            }
+            return { strategy: 'full_scan', estimatedRows: 1000 };
+        }
        ensureOpen() {
            if (!this.opened)
                throw new DatabaseError('AriaEngine not opened', 'DB_NOT_OPEN');
@@ -0,0 +1,67 @@
+/**
+ * AriaEngine Performance Benchmark
+ * 测量 insert/find/update/delete 在不同数据量级下的性能
+ */
+import { AriaEngine } from './index';
+import { createSchema } from '../../table/schema';
+
+interface BenchResult {
+  name: string;
+  rows: number;
+  ops: number;
+  totalMs: number;
+  opsPerSec: number;
+}
+
+function createTestSchema() {
+  return createSchema('bench', {
+    id: { type: 'string', primaryKey: true },
+    name: { type: 'string' },
+    value: { type: 'number', index: true },
+  });
+}
+
+async function timeIt(name: string, fn: () => Promise<void>): Promise<number> {
+  const start = performance.now();
+  await fn();
+  return performance.now() - start;
+}
+
+export async function runBenchmarks(): Promise<BenchResult[]> {
+  const results: BenchResult[] = [];
+  const sizes = [100, 1000, 10000, 100000];
+
+  for (const size of sizes) {
+    const engine = new AriaEngine({ storageBackend: 'memory' });
+    await engine.open('bench-db', 1);
+    await engine.createTable(createTestSchema());
+
+    // Insert
+    const rows = [];
+    for (let i = 0; i < size; i++) {
+      rows.push({ id: `${i}`, name: `User${i}`, value: i * 10 });
+    }
+    const insertMs = await timeIt(`insert-${size}`, () => engine.insert('bench', rows));
+    results.push({ name: `insert-${size}`, rows: size, ops: size, totalMs: insertMs, opsPerSec: Math.round(size / (insertMs / 1000)) });
+
+    // Find by PK
+    const findMs = await timeIt(`find-pk-${size}`, () => engine.find('bench', { table: 'bench', where: { id: `${size - 1}` } }));
+    results.push({ name: `find-pk-${size}`, rows: size, ops: 1, totalMs: findMs, opsPerSec: Math.round(1000 / findMs) });
+
+    // Find by index
+    const findIdxMs = await timeIt(`find-idx-${size}`, () => engine.find('bench', { table: 'bench', where: { value: (size - 1) * 10 } }));
+    results.push({ name: `find-idx-${size}`, rows: size, ops: 1, totalMs: findIdxMs, opsPerSec: Math.round(1000 / findIdxMs) });
+
+    // Update
+    const updateMs = await timeIt(`update-${size}`, () => engine.update('bench', { table: 'bench', where: { id: `${size - 1}` } }, { name: 'Updated' }));
+    results.push({ name: `update-${size}`, rows: size, ops: 1, totalMs: updateMs, opsPerSec: Math.round(1000 / updateMs) });
+
+    // Delete
+    const deleteMs = await timeIt(`delete-${size}`, () => engine.delete('bench', { table: 'bench', where: { id: `${size - 1}` } }));
+    results.push({ name: `delete-${size}`, rows: size, ops: 1, totalMs: deleteMs, opsPerSec: Math.round(1000 / deleteMs) });
+
+    await engine.close();
+  }
+
+  return results;
+}
@@ -22,6 +22,7 @@ import { IndexedDBBackend, MemoryBackend, type IStorageBackend } from './store/b
 import { OPFSBackend } from './store/opfs_backend';
 import { MVCCManager } from './transaction/mvcc';
 import { BloomFilter } from './index/bloom';
+import { BufferPool, type PageIO } from './buffer/pool';

 // ---------------------------------------------------------------------------
 //  AriaEngine
@@ -52,6 +53,9 @@ export class AriaEngine implements IStorageEngine {
  private txnSnapshot: Map<string, Record<string, unknown>> | null = null;
  private gcCounter = 0;

+  // Buffer Pool（页面缓存，减少磁盘 I/O）
+  private bufferPool!: BufferPool;
+
  constructor(config: AriaEngineConfig = {}) {
    this.config = { ...DEFAULT_ARIA_CONFIG, ...config };
  }
@@ -74,6 +78,15 @@ export class AriaEngine implements IStorageEngine {
    }
    await this.backend.open(dbName);

+    // 2a. 初始化 Buffer Pool（页面缓存）
+    const pageIO: PageIO = {
+      readPage: async (pageId) => this.backend.read(`pg_${pageId}`),
+      writePage: async (pageId, data) => this.backend.write(`pg_${pageId}`, data),
+      allocatePageId: async () => Date.now(),
+      freePageId: async () => {},
+    };
+    this.bufferPool = new BufferPool(pageIO, this.config.bufferPoolPages);
+
    // 2. 构建 SSTableStore
    const sstableStore = this.createSSTableStore();

@@ -909,6 +922,90 @@ export class AriaEngine implements IStorageEngine {
    return stats;
  }

+  /**
+   * REINDEX: 重建指定表的所有二级索引
+   */
+  async reindexTable(tableName: string): Promise<number> {
+    this.ensureOpen();
+    this.ensureTable(tableName);
+    const schema = this.schemas.get(tableName)!;
+    let rebuiltCount = 0;
+
+    for (const [colName, colDef] of Object.entries(schema.columns)) {
+      if (!colDef.index && !colDef.unique && !colDef.primaryKey) continue;
+      const idxKey = `${tableName}:idx:${colName}`;
+      const idxLsm = this.secondaryIndexes.get(idxKey);
+      if (!idxLsm) continue;
+
+      // 清空旧索引
+      await idxLsm.clear();
+      rebuiltCount++;
+
+      // 从主 LSM 重建索引
+      const rows = this.getAllRows(tableName);
+      for (const row of rows) {
+        const val = row[colName];
+        if (val !== undefined && val !== null) {
+          idxLsm.put(`${String(val)}:${row[this.tablePKs.get(tableName)!]}`, { pk: row[this.tablePKs.get(tableName)!] });
+        }
+      }
+    }
+    return rebuiltCount;
+  }
+
+  /**
+   * VACUUM: 压缩 LSM + 清理碎片
+   */
+  async vacuum(): Promise<{ compactedLevels: number; gcVersions: number }> {
+    this.ensureOpen();
+    // 强制 flush memtable
+    await this.lsm.flush();
+    // 压缩各层级
+    for (let level = 0; level < 6; level++) {
+      if (this.lsm.getStats().levelCounts[level] >= 2) {
+        (this.lsm as any).compactLevelSync(level);
+      }
+    }
+    // GC MVCC 版本（保留最新 10 个）
+    const beforeGC = this.mvcc.getActiveTxnCount?.() ?? 0;
+    this.mvcc.gc(10);
+    return { compactedLevels: 6, gcVersions: beforeGC };
+  }
+
+  /**
+   * 查询优化器：估算各索引成本，选择最优方案
+   */
+  estimateQueryCost(tableName: string, query: QueryPlan): { strategy: string; estimatedRows: number } {
+    const schema = this.schemas.get(tableName);
+    if (!schema || !query.where) return { strategy: 'full_scan', estimatedRows: 0 };
+
+    const pkCol = this.tablePKs.get(tableName)!;
+    for (const [col, condition] of Object.entries(query.where)) {
+      if (col === '$and' || col === '$or' || col === '$not') continue;
+
+      // PK 等值 → 最快，估计 1 行
+      if (col === pkCol && (typeof condition !== 'object' || (condition as any).$eq)) {
+        return { strategy: 'pk_lookup', estimatedRows: 1 };
+      }
+
+      // 索引列等值 → 快
+      const colDef = schema.columns[col];
+      if (colDef?.index || colDef?.unique) {
+        if (typeof condition !== 'object' || (condition as any).$eq) {
+          return { strategy: `index_eq:${col}`, estimatedRows: 1 };
+        }
+        if ((condition as any).$in && Array.isArray((condition as any).$in)) {
+          return { strategy: `index_in:${col}`, estimatedRows: (condition as any).$in.length };
+        }
+        if ((condition as any).$gt || (condition as any).$lt || (condition as any).$gte || (condition as any).$lte) {
+          return { strategy: `index_range:${col}`, estimatedRows: 100 };
+        }
+      }
+    }
+
+    return { strategy: 'full_scan', estimatedRows: 1000 };
+  }
+
  private ensureOpen(): void {
    if (!this.opened) throw new DatabaseError('AriaEngine not opened', 'DB_NOT_OPEN');
  }
@@ -13,6 +13,7 @@ export class OPFSBackend implements IStorageBackend {
  private root: FileSystemDirectoryHandle | null = null;
  private dbDir: FileSystemDirectoryHandle | null = null;
  private dbName = '';
+  private writeQueue: Promise<void> = Promise.resolve();

  async open(name: string): Promise<void> {
    this.dbName = name;
@@ -42,19 +43,21 @@ export class OPFSBackend implements IStorageBackend {

  async write(key: string, data: ArrayBuffer): Promise<void> {
    if (!this.dbDir) return;
-    const fh = await this.dbDir.getFileHandle(key, { create: true });
-    const writable = await fh.createWritable();
-    await writable.write(data);
-    await writable.close();
+    this.writeQueue = this.writeQueue.then(async () => {
+      const fh = await this.dbDir!.getFileHandle(key, { create: true });
+      const writable = await fh.createWritable();
+      await writable.write(data);
+      await writable.close();
+    });
+    return this.writeQueue;
  }

  async delete(key: string): Promise<void> {
    if (!this.dbDir) return;
-    try {
-      await this.dbDir.removeEntry(key);
-    } catch {
-      // 文件不存在则忽略
-    }
+    this.writeQueue = this.writeQueue.then(async () => {
+      try { await this.dbDir!.removeEntry(key); } catch { /* ignore */ }
+    });
+    return this.writeQueue;
  }

  async listKeys(): Promise<string[]> {