feat: v0.2.4 惰性扫描 + 写背压 + 内存预算 + ANALYZE + 加密 + Savepoint + 在线备份

src/engine/aria/index.ts

@@ -302,6 +302,7 @@ export class AriaEngine implements IStorageEngine {
     }
 
     this.opCounter += rows.length;
+    this.checkMemoryBudget();
     await this.checkpointManager.tick();
     this.tryGC();
     return pks;
@@ -519,6 +520,49 @@ export class AriaEngine implements IStorageEngine {
     this.currentTxnId = null;
   }
 
+  // ---- Savepoint 嵌套事务 ----
+
+  private savepoints: Map<string, { txnId: number; snapshot: Map<string, Record<string, unknown>> | null }> = new Map();
+
+  async savepoint(name: string): Promise<void> {
+    if (!this.currentTxnId) throw new DatabaseError('No active transaction for savepoint', 'TX_NONE');
+    if (this.savepoints.has(name)) throw new DatabaseError(`Savepoint "${name}" already exists`, 'SAVEPOINT_EXISTS');
+    // 保存当前事务快照
+    this.savepoints.set(name, {
+      txnId: this.currentTxnId,
+      snapshot: this.txnSnapshot ? new Map(this.txnSnapshot) : null,
+    });
+  }
+
+  async rollbackToSavepoint(name: string): Promise<void> {
+    const sp = this.savepoints.get(name);
+    if (!sp) throw new DatabaseError(`Savepoint "${name}" not found`, 'SAVEPOINT_NOT_FOUND');
+    // 恢复到 savepoint 时的快照
+    this.txnSnapshot = sp.snapshot ? new Map(sp.snapshot) : null;
+    // 清除此 savepoint 之后的所有 savepoint
+    let found = false;
+    for (const [k] of this.savepoints) {
+      if (k === name) { found = true; continue; }
+      if (found) this.savepoints.delete(k);
+    }
+  }
+
+  async releaseSavepoint(name: string): Promise<void> {
+    if (!this.savepoints.has(name)) throw new DatabaseError(`Savepoint "${name}" not found`, 'SAVEPOINT_NOT_FOUND');
+    this.savepoints.delete(name);
+  }
+
+  // ---- 在线备份 ----
+
+  async backup(): Promise<Record<string, Record<string, unknown>[]>> {
+    this.ensureOpen();
+    const result: Record<string, Record<string, unknown>[]> = {};
+    for (const tableName of this.schemas.keys()) {
+      result[tableName] = this.getAllRows(tableName);
+    }
+    return result;
+  }
+
   // =======================================================================
   //  内部
   // =======================================================================
@@ -821,6 +865,50 @@ export class AriaEngine implements IStorageEngine {
     }
   }
 
+  /** 检查内存预算，超出时强制 flush + GC */
+  private checkMemoryBudget(): void {
+    const maxBytes = this.config.maxMemoryMB * 1024 * 1024;
+    const used = this.lsm.getEstimatedMemory();
+    if (used > maxBytes) {
+      this.lsm.flush().catch(() => {});
+      this.mvcc.gc(50);
+    }
+  }
+
+  /**
+   * ANALYZE: 收集表统计信息
+   * 返回行数、平均行大小、索引深度等
+   */
+  async analyzeTable(tableName: string): Promise<Record<string, unknown>> {
+    this.ensureOpen();
+    this.ensureTable(tableName);
+    const rows = this.getAllRows(tableName);
+    const stats: Record<string, unknown> = {
+      table: tableName,
+      rowCount: rows.length,
+      avgRowSize: rows.length > 0
+        ? Math.round(rows.reduce((s, r) => s + JSON.stringify(r).length, 0) / rows.length)
+        : 0,
+      indexDepth: this.lsm.getStats().levelCounts.filter((c: number) => c > 0).length,
+      sstableCount: this.lsm.getStats().sstableCount,
+      memtableSize: this.lsm.getStats().memtableSize,
+      estimatedMemory: this.lsm.getEstimatedMemory(),
+    };
+
+    // 列基数统计
+    const schema = this.schemas.get(tableName);
+    if (schema && rows.length > 0) {
+      const columnStats: Record<string, unknown> = {};
+      for (const colName of Object.keys(schema.columns)) {
+        const values = new Set(rows.map((r) => String(r[colName])));
+        columnStats[colName] = { distinctValues: values.size };
+      }
+      stats.columnStats = columnStats;
+    }
+
+    return stats;
+  }
+
   private ensureOpen(): void {
     if (!this.opened) throw new DatabaseError('AriaEngine not opened', 'DB_NOT_OPEN');
   }