arXiv subjects

Zhuoyue Zhao

Publications and source records attributed to Zhuoyue Zhao.

4 recordsLinked to original sources

arXiv2026

Index-Assisted Stratified Sampling for Online Aggregation

Ad-hoc queries over frequently updated data in a flat schema are common in real-time data analysis applications and often require very low latency. Online aggregation can achieve so by providing approximate aggregation answers with confidence bound guarantees. It relies on the ability to draw samples online in a linear time to sample size rather than database size, which can be supported by index-assisted Sampling-based Approximate Query Processing (S-AQP) systems. However, the query latencies of approximate queries in these systems can still suffer from excessive sampling cost required to achieve a desired confidence bound, due to increased sample size for data with high variance in value distribution and selectivity. Classic stratified sampling methods with Neyman allocation can minimize sample size in theory, but several challenges prevent it from being applicable in index-assisted S-AQP systems, including requiring apriori statistics, high optimization cost, and inaccurate sampling cost model based on sample size. Towards that, we design index-assisted stratified sampling for online aggregation, which features a two-phase sampling framework. Samples drawn from first phase are used for both online aggregation and optimizing future sampling cost, while the second phase continues the online aggregation using the optimized strata. We prove optimal stratification and sample size allocation strategies for index-based sampling cost model, and design several greedy and dynamic programming based optimization methods to balance optimization cost and effectiveness in cost reduction. We evaluate our methods on several real-world and synthetic datasets and queries, and the results show ours consistently achieve good speedup and, in extreme cases, up to 3x speedup and 98708x speedup, when compared to index-assisted uniform sampling and classic scan-based stratified sampling respectively.

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arXiv2025

SABER: A SQL-Compatible Semantic Document Processing System Based on Extended Relational Algebra

The emergence of large-language models (LLMs) has enabled a new class of semantic data processing systems (SDPSs) to support declarative queries against unstructured documents. Existing SDPSs are, however, lacking a unified algebraic foundation, making their queries difficult to compose, reason, and optimize. We propose a new semantic algebra, SABER (Semantic Algebra Based on Extended Relational algebra), opening the possibility of semantic operations' logical plan construction, optimization, and formal correctness guarantees. We further propose to implement SABER in a SQL-compatible syntax so that it natively supports mixed structured/unstructured data processing. With SABER, we showcase the feasibility of providing a unified interface for existing SDPSs so that it can effectively mix and match any semantically-compatible operator implementation from any SDPS, greatly enhancing SABER's applicability for community contributions.

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arXiv2023

GLIN: A (G)eneric (L)earned (In)dexing Mechanism for Complex Geometries

Although spatial indexes shorten the query response time, they rely on complex tree structures to narrow down the search space. Such structures in turn yield additional storage overhead and take a toll on index maintenance. Recently, there have been a flurry of efforts attempting to leverage Machine-Learning (ML) models to simplify the index structures. However, existing geospatial indexes can only index point data rather than complex geometries such as polygons and trajectories that are widely available in geospatial data. As a result, they cannot efficiently and correctly answer geometry relationship queries. This paper introduces GLIN, an indexing mechanism for spatial relationship queries on complex geometries. To achieve that, GLIN transforms geometries to Z-address intervals, and then harnesses an existing order-preserving learned index to model the cumulative distribution function between these intervals and the record positions. The lightweight learned index greatly reduces indexing overhead and provides faster or comparable query latency. Most importantly, GLIN augments spatial query windows to support queries exactly for common spatial relationships. Our experiments on real-world and synthetic datasets show that GLIN has 80\%-90\% lower storage overhead than Quad-Tree and 60% - 80% than R-tree and 30% - 70% faster query on medium selectivity. Moreover, GLIN's maintenance throughput is 1.5 times higher on insertion and 3 - 5 times higher on deletion.

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arXiv2017

InferSpark: Statistical Inference at Scale

The Apache Spark stack has enabled fast large-scale data processing. Despite a rich library of statistical models and inference algorithms, it does not give domain users the ability to develop their own models. The emergence of probabilistic programming languages has showed the promise of developing sophisticated probabilistic models in a succinct and programmatic way. These frameworks have the potential of automatically generating inference algorithms for the user defined models and answering various statistical queries about the model. It is a perfect time to unite these two great directions to produce a programmable big data analysis framework. We thus propose, InferSpark, a probabilistic programming framework on top of Apache Spark. Efficient statistical inference can be easily implemented on this framework and inference process can leverage the distributed main memory processing power of Spark. This framework makes statistical inference on big data possible and speed up the penetration of probabilistic programming into the data engineering domain.

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