About me

I am a postdoc in the Data Systems Group at the University of Waterloo. I am working with Renée J. Miller on data lakes. I worked with Tamer Özsu on graph data management. Previously, I was a postdoc at the University of Lyon (Lyon 1), working with Angela Bonifati. I received my PhD in computer science from the University of Clermont Auvergne, advised by Farouk Toumani. I also worked closely with Inria and Oracle Labs (Zurich).

I work on data systems. My recent focus is on data systems and large language models, collectively referred to as Data Intelligence Platforms. My research interests include the following:

• Query Processing: indexing methods; stream processing; multimodal and heterogenous data; natural language queries.
• Data Lakes: data discovery; vector and semantic search; metadata management; data integration; open lakehouse and AI.

Key Works

• Ada-ef (SIGMOD’ 26): Adaptive vector search with declarative recall.
• BIC (VLDB’ 24, KDD’ 21): Incremental computing framework for sliding window query processing over data streams.
• SUDAF (ACM TODS 2024): Processing and optimizing queries with user-defined aggregate functions.
• RLC Index (ICDE’ 23): Indexing multi-hop, recursive relationships on graphs.
• LazyVLM: Scaling vision-language-model–based video analytics.

Publications

DBLP: Chao Zhang 0045

• Distribution-Aware Exploration for Adaptive HNSW Search.
  Chao Zhang, Renée J. Miller.
  SIGMOD 2026 (accepted for publication).

• Indexing Techniques for Graph Reachability Queries.
  Chao Zhang, Angela Bonifati, M. Tamer Özsu.
  ACM CSUR 2025 (accepted for publication). [Extended version].

• Incremental Sliding Window Connectivity over Streaming Graphs.
  Chao Zhang, Angela Bonifati, M. Tamer Özsu.
  VLDB 2024. [Extended version] [Code]

• Sharing Queries with Nonequivalent User-Defined Aggregate Functions.
  Chao Zhang, Farouk Toumani.
  ACM TODS 2024, Volume 49, Issue 2.

• An Overview of Reachability Indexes on Graphs.
  Chao Zhang, Angela Bonifati, M. Tamer Özsu.
  SIGMOD 2023 (Tutorial). [Slides (short)] [Slides (full)]

• A Reachability Index for Recursive Label-Concatenated Graph Queries.
  Chao Zhang, Angela Bonifati, Hugo Kapp, Vlad Ioan Haprian, Jean-Pierre Lozi.
  ICDE 2023. [Extended version] [Code] [Slides]

• Efficient Incremental Computation of Aggregations over Sliding Windows.
  Chao Zhang, Reza Akbarinia, Farouk Toumani.
  KDD 2021. [Code]

• SUDAF: Sharing User-Defined Aggregate Functions.
  Chao Zhang, Farouk Toumani, Bastien Doreau.
  ICDE 2020 (Demo).

• Sharing Computations for User-Defined Aggregate Functions.
  Chao Zhang, Farouk Toumani.
  EDBT 2020.

• Symmetric and Asymmetric Aggregate Functions in Massively Parallel Computing.
  Chao Zhang.
  VLDB PhD Workshop 2017.

Preprints & Submissions

• LazyVLM: Neuro-Symbolic Approach to Video Analytics.
  Xiangru Jian, Wei Pang, Zhengyuan Dong, Chao Zhang, M. Tamer Özsu.

• GRAPHOMNI: A Comprehensive and Extendable Benchmark Framework for Large Language Models on Graph-theoretic Tasks.
  Hao Xu, Xiangru Jian, Xinjian Zhao, Wei Pang, Chao Zhang, Suyuchen Wang, Qixin Zhang, Zhengyuan Dong, Joao Monteiro, Bang Liu, Qiuzhuang Sun, Tianshu Yu.

• Low-Latency Sliding Window Connectivity.
  Chao Zhang, Angela Bonifati, M. Tamer Özsu.

• Parallelization of Incremental Aggregations over Sliding Windows.
  Chao Zhang, Reza Akbarinia, Farouk Toumani.

Presentations

• Towards Efficient and Trustworthy Query Processing over Heterogeneous Data Lakes.
  • School of Information Technology, York University, November 20, 2025.
  • Department of Computer Science, University of Lyon (Lyon 1) / CNRS LIRIS, October 13, 2025
• Towards High-Throughput and Low-Latency Sliding Window Processing over Data Streams.
  • School of Computer Science, University of Guelph, June 18, 2025.
  • School of Information Technology, York University, April 2, 2024.
• Big Graph Processing Systems (with Angela Bonifati).
  • MDD 2022 Summer School, Bastia, June 19-23, 2022.
  • eBISS 2022 Summer School, Cesena, July 4-8, 2022.

Service

• Program Committee Member:
  • SIGMOD: 2025, 2024, 2022
  • VLDB: 2026, 2025, 2024, 2023
  • ICDE: 2026
  • ACM SoCC: 2025, 2024, 2023
  • BDA: 2021 (Demo).
• Invited Journal Reviewer:
  • ACM TODS, VLDBJ, IEEE TKDE

Awards

• Best Paper Award in BDA 2021, French Data Management Community.
• Best PhD Thesis (runner-up) in BDA 2020, French Data Management Community.
• Full scholarship for the 1st Big Sky Earth training school in DLR, Germany, April 4th-9th, 2016.

Teaching

• CS 348: Introduction to Database Management at the University of Waterloo, Winter 2023.
• Big Data Processing: Apache Spark in Action at the University of Clermont Auvergne, Spring 2022.
• Semantic Web (labs) at the University of Clermont Auvergne, Fall 2021.

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