面向对象空间编程的基于时间轨迹图的自动预取

中文摘要 AI 辅助

依赖的数据库访问可能会在请求的关键路径上序列化应用程序与数据库之间的往返。跨遍历步骤的规划需要知道计算可能遵循哪些关系，以及发现的对象如何成为后续执行的上下文。我们识别出一种编程模型契约，通过可检查的访问路径和显式的遍历延续来暴露这些信息。我们在对象空间编程（OSP）中展示了这一契约，其中遍历器（walker）遍历类型化的对象图并执行节点类型特定的代码。我们引入了时间轨迹图（TTG），这是一种有界的、针对特定请求的候选对象及遍历衍生转换的图。在遍历器生成时，TTG构建器从请求的起始节点出发，在活动图上组合静态提取的访问和延续规则。一个异步预取器在遍历器执行时加载计划的对象。我们在Jac/PostgreSQL中实现了TTG，并评估了覆盖线性、多跳、递归和值依赖遍历的四个应用。TTG在三个应用中改善了端到端延迟，相比标准运行时实现了最高2.99倍的加速。与手动分阶段预取的比较刻画了自动跨步骤规划的收益和成本。评估还表明，规划开销可能超过所避免的需求延迟，并且值依赖的控制可能引入有界的过度预取。

英文摘要

Dependent database accesses can serialize application--database round trips on a request's critical path. Planning across traversal steps requires knowing both which relationships a computation may follow and how discovered objects become subsequent execution contexts. We identify a programming-model contract that exposes this information through inspectable access paths and explicit traversal continuation. We demonstrate this contract in Object-Spatial Programming (OSP), where walkers traverse a typed object graph and execute node-type-specific code. We introduce the Temporal Trace Graph (TTG), a bounded, request-specific graph of candidate objects and traversal-derived transitions. At walker spawn, the TTG Builder composes statically extracted access and continuation rules over the live graph from the request's starting node. An asynchronous prefetcher loads planned objects while the walker executes. We implement TTG in Jac/PostgreSQL and evaluate four applications covering linear, multi-hop, recursive, and value-dependent traversals. TTG improves end-to-end latency in three applications, achieving up to 2.99x speedup over the stock runtime. Comparisons with manually staged prefetching characterize the benefits and costs of automatic cross-step planning. The evaluation also shows that planning overhead can exceed avoided demand latency and that value-dependent control can introduce bounded overfetch.

发表机构

• University of Michigan（密歇根大学）

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