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arXiv · 2003.02391

Order-Preserving Key Compression for In-Memory Search Trees

Huanchen Zhang·Xiaoxuan Liu·David G. Andersen·Michael Kaminsky·Kimberly Keeton·Andrew Pavlo
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Abstract

We present the High-speed Order-Preserving Encoder (HOPE) for in-memory search trees. HOPE is a fast dictionary-based compressor that encodes arbitrary keys while preserving their order. HOPE's approach is to identify common key patterns at a fine granularity and exploit the entropy to achieve high compression rates with a small dictionary. We first develop a theoretical model to reason about order-preserving dictionary designs. We then select six representative compression schemes using this model and implement them in HOPE. These schemes make different trade-offs between compression rate and encoding speed. We evaluate HOPE on five data structures used in databases: SuRF, ART, HOT, B+tree, and Prefix B+tree. Our experiments show that using HOPE allows the search trees to achieve lower query latency (up to 40\% lower) and better memory efficiency (up to 30\% smaller) simultaneously for most string key workloads.

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Huanchen Zhang, Xiaoxuan Liu, David G. Andersen, Michael Kaminsky, Kimberly Keeton, Andrew Pavlo. 2020-03-05. Order-Preserving Key Compression for In-Memory Search Trees. https://arxiv.org/abs/2003.02391

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