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arXiv · 2406.19143

QSketch: An Efficient Sketch for Weighted Cardinality Estimation in Streams

Yiyan Qi·Rundong Li·Pinghui Wang·Yufang Sun·Rui Xing
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Abstract

Estimating cardinality, i.e., the number of distinct elements, of a data stream is a fundamental problem in areas like databases, computer networks, and information retrieval. This study delves into a broader scenario where each element carries a positive weight. Unlike traditional cardinality estimation, limited research exists on weighted cardinality, with current methods requiring substantial memory and computational resources, challenging for devices with limited capabilities and real-time applications like anomaly detection. To address these issues, we propose QSketch, a memory-efficient sketch method for estimating weighted cardinality in streams. QSketch uses a quantization technique to condense continuous variables into a compact set of integer variables, with each variable requiring only 8 bits, making it 8 times smaller than previous methods. Furthermore, we leverage dynamic properties during QSketch generation to significantly enhance estimation accuracy and achieve a lower time complexity of $O(1)$ for updating estimations upon encountering a new element. Experimental results on synthetic and real-world datasets show that QSketch is approximately 30\% more accurate and two orders of magnitude faster than the state-of-the-art, using only $1/8$ of the memory.

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Yiyan Qi, Rundong Li, Pinghui Wang, Yufang Sun, Rui Xing. 2024-06-27. QSketch: An Efficient Sketch for Weighted Cardinality Estimation in Streams. https://arxiv.org/abs/2406.19143

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