Adaptive filters, such as telescoping and adaptive cuckoo filters, update their representation upon detecting a false positive to avoid repeating the same error in the future. Adaptive filters require an auxiliary structure, typically much larger than the main filter and often residing on slow storage, to facilitate adaptation. However, existing adaptive filters are not practical and have seen no adoption in real-world systems due to two main reasons. Firstly, they offer weak adaptivity guarantees, meaning that fixing a new false positive can cause a previously fixed false positive to come back. Secondly, the sub-optimal design of the auxiliary structure results in adaptivity overheads so substantial that they can actually diminish the overall system performance compared to a traditional filter. In this paper, we design and implement AdaptiveQF, the first practical adaptive filter with minimal adaptivity overhead and strong adaptivity guarantees, which means that the performance and false-positive guarantees continue to hold even for adversarial workloads. The AdaptiveQF is based on the state-of-the-art quotient filter design and preserves all the critical features of the quotient filter such as cache efficiency and mergeability. Furthermore, we employ a new auxiliary structure design which results in considerably low adaptivity overhead and makes the AdaptiveQF practical in real systems.

翻译：自适应滤波器（如伸缩滤波器与自适应布谷鸟滤波器）在检测到误判时会更新其表征，以避免未来重复出现相同错误。这类滤波器需要借助辅助结构（通常远大于主滤波器且常驻于慢速存储）来实现自适应功能。然而，现有自适应滤波器因两大主因缺乏实用性且未被真实系统采纳：其一，它们仅提供弱自适应性保证，即修复新误判时可能导致已修复的误判重新出现；其二，辅助结构的次优设计导致过高的自适应性开销，相较于传统滤波器反而可能降低整体系统性能。本文设计实现了AdaptiveQF——首款兼具极低自适应性开销与强自适应性保证的实用自适应滤波器，其性能与误判保证即使在对抗性工作负载下仍能保持。AdaptiveQF基于最先进的商滤波器设计，保留了商滤波器的所有关键特性（如缓存效率与可合并性）。此外，我们采用的新型辅助结构设计显著降低了自适应性开销，使AdaptiveQF在真实系统中具备实用价值。