构建跳表索引

项目概述

本项目实现一个面向 ordered in-memory indexing 的完整系统，核心要解决的问题是 maintaining a sorted structure with logarithmic insert, delete, and range queries without rebalance cost。整体由 Level generator、Node inserter、Search path、Range scanner、Delete marker 五个模块组成，每个模块单一职责、可独立测试，最后通过集成测试验证端到端正确性。设计上把 a degenerate promotion sequence that produces tall, sparse levels and degrades search toward linear 作为第一类需求先行处理，而非事后再补。

架构与关键决策

数据模型为 a multi-level linked list where each level skips over more nodes, giving expected logarithmic search through random promotion。Level generator 定义其余阶段共同依赖的数据形状并在边界处校验输入；Node inserter 承载 ordered in-memory indexing 的正确性逻辑；Search path 专门处理 a degenerate promotion sequence that produces tall, sparse levels and degrades search toward linear，在失败路径上给出明确的拒绝、重试或降级策略；Range scanner 提供可观测性，每次操作输出带关联 id 的结构化事件；Delete marker 在过载时按既定方式降级，避免过载演变为数据损坏。配置与代码分离，使风险变更可经 diff 审阅。

实施与测试

按五个阶段依次实现 Level generator、Node inserter、Search path、Range scanner、Delete marker，每阶段配套聚焦单测。集成测试组合各模块并驱动真实 ordered in-memory indexing 场景：先验证正常路径，再刻意触发 a degenerate promotion sequence that produces tall, sparse levels and degrades search toward linear 并断言系统降级而非损坏。所有依赖均在进程内或被桩替换，用例在 CI 中确定可复现。

限制与后续

• 单区域设计，多区域复制超出范围。
• Level generator 默认进程内，未水平共享。
• 无鉴权层，假定部署在强制身份的边缘之后。

代码示例

# setup for skip-list-index
pnpm init
pnpm add fastify pino
pnpm add -D typescript tsx vitest

skip_list_index/
├── src/index.ts
├── src/level-generator.ts
├── src/node-inserter.ts
├── tests/skip_list_index.test.ts
└── package.json

// Level generator: ordered in-memory indexing core
export function levelgenerator(input: LevelgeneratorInput): LevelgeneratorResult {
  // Build the level generator that anchors ordered in-memory indexing and defines the core data shape.
  return processLevelgenerator(input);
}

// Node inserter — handles ordered in-memory indexing Add the node inserter so
export class Nodeinserter {
  constructor(private opts: NodeinserterOptions) {}
  async run(ctx: Context): Promise<NodeinserterOutput> {
    return this.execute(ctx);
  }
}

// Search path: ordered in-memory indexing stage
export const searchpath = (next: Next) => async (req: Request) => {
  const out = await transform(req);
  return next(out);
};

// Range scanner for ordered in-memory indexing
export async function rangescanner(stream: AsyncIterable<Chunk>): Promise<Aggregate> {
  let acc = init();
  for await (const c of stream) acc = merge(acc, c);
  return acc;
}

// Delete marker: ordered in-memory indexing finalization
export function deletemarker(state: State): Result {
  validate(state);
  return finalize(state);
}

# run the ordered in-memory indexing test suite
pnpm vitest run