I am a Senior Researcher at Microsoft Gray Systems Lab since May 2025. I work on optimizing (and providing guarantees for) database systems.
I got my Ph.D. from University of Wisconsin-Madison advised by Paraschos Koutris.
In 2020, I received my B.S. in Math from National University of Singapore. There, I was advised by Prof. Jonathan Scarlett on neural architectural search.
News
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June 2026: I am honored to receive the 2026 ACM SIGMOD Jim Gray Doctoral Dissertation Award. Here is my dissertation.
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March 2026: I gave talks at Wisconsin and CMU Database Group on my recent use of AI agents for industrial-grade query optimization.
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December 2025: FlowLog has been accepted to VLDB 2026. Visit our repo if you want to try running it!
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November 2025: I gave a talk at NWDS on our recent research efforts on "Modernizing the Yannakakis Algorithm".
Publications (* denotes alphabetical authorship)
2026
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Rubberband: Memory-Elastic, Skew-Tolerant GPU Hash Joins
Hangdong Zhao, Rathijit Sen, Craig Peeper, Matteo Interlandi
ADMS'26 (VLDB Workshop) -
One Join Order Does Not Fit All: Reducing Intermediate Results with Per-Split Query Plans
Yujun He, Hangdong Zhao, Simon Frisk, Yifei Yang, Kevin Kristensen, Paraschos Koutris, Xiangyao Yu
VLDB'26 -
FlowLog: Efficient and Extensible Datalog via Incrementality flowlog-rs.com github
Hangdong Zhao, Zhenghong Yu, Srinag Rao, Simon Frisk, Zhiwei Fan, Paraschos Koutris
VLDB'26 -
Demo of SemWeave: Semantic Common Expressions for LLM-powered Query Processing
Md. Tareq Mahmood, Venkatesh Emani, Hangdong Zhao, Shivaram Venkataraman
SIGMOD'26 Demo -
I Can't Believe It's Not Yannakakis: Pragmatic Bitmap Filters in Microsoft SQL Server slides
Hangdong Zhao, Yuanyuan Tian, Rana Alotaibi, Bailu Ding, Nicolas Bruno, Jesús Camacho-Rodríguez, Vassilis Papadimos, Ernesto Cervantes Juárez, Cesar Galindo-Legaria, Carlo Curino
CIDR'26
2025
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*Circuit Bounds for Conjunctive Queries with Self-joins
Austen Fan, Paraschos Koutris, Hangdong Zhao
PODS'25 -
Output-sensitive Conjunctive Query Evaluation SIGMOD Record podcast
Shaleen Deep, Hangdong Zhao, Austen Fan, Paraschos Koutris
PODS'25
Best Paper Award (invited to J. ACM)
SIGMOD Research Highlight Award
2024
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Evaluating Datalog over Semirings: A Grounding-based Approach Datalog 2.0'24
Hangdong Zhao, Shaleen Deep, Paraschos Koutris, Sudeepa Roy, Val Tannen
PODS'24 -
*Tight Bounds of Circuits for Sum-Product Queries slides
Austen Fan, Paraschos Koutris, Hangdong Zhao
PODS'24
Distinguished Paper Award (invited to J. ACM) -
Predicate Transfer: Efficient Pre-Filtering on Multi-Join Queries
Yifei Yang, Hangdong Zhao, Xiangyao Yu, Paraschos Koutris
CIDR'24 -
Conjunctive Queries with Negation and Aggregation: A Linear Time Characterization slides demo TODS'25
Hangdong Zhao, Austen Fan, Xiating Ouyang, Paraschos Koutris
PODS'24
Distinguished Paper Award (invited to TODS)
2023
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*The Fine-Grained Complexity of Boolean Conjunctive Queries and Sum-Product Problems slides poster
Austen Fan, Paraschos Koutris, Hangdong Zhao
ICALP'23 -
Space-Time Tradeoffs for Conjunctive Queries with Access Patterns slides TODS'25
Hangdong Zhao, Shaleen Deep, Paraschos Koutris
PODS'23
Distinguished Paper Award (invited to TODS)
2021
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On Architecture Selection for Linear Inverse Problems with Untrained Neural Networks
Yang Sun, Hangdong Zhao, Jonathan Scarlett
Entropy, 23(11), 1481
Teaching Experience (TA)
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CS 577 Intro to Algorithms: Spring 2022 (Prof. Jin-yi Cai), Fall 2021 (Prof. Eric Bach)
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CS 544 Intro to Big Data Systems: Fall 2023 (Prof. Tyler R. Caraza-Harter)
