START — Self-Tuning Adaptive Radix Tree

Index structures like the Adaptive Radix Tree (ART) are a central part of in-memory database systems. However, we found that radix nodes that index a single byte are not optimal for read-heavy workloads. In this work, we introduce START, a self-tuning variant of ART that uses nodes spanning multiple key-bytes. To determine where to introduce these new node types, we propose a cost model and an optimizer. These components allow us to fine-tune an existing ART, reducing its overall height, and improving performance. As a result, START performs on average 85 % faster than a regular ART on a wide variety of read-only workloads and 45% faster for read-mostly workloads.