Zhekai Jiang

Education Docteur ès sciences | Computer and communication sciences 2024 – 2026 EPFL Bachelor of software engineering | Software engineering 2019 – 2024 McGill University Professionals experiences Research intern 2023–2023 Oracle LabsResearch intern 2022–2022 EPFL ResearchStructure-guided query optimization in database systems During my PhD at EPFL, I am currently working on algorithms for query optimization in database systems. In particular, I exploit structural information of the queries to help reason about their theoretical worst-case asymptotic complexity and guide query optimizers towards good execution plans in practice.In the case of conjunctive (select-project-join) queries, I proposed a query optimization approach based on "meta-decompositions", a representation that succinctly encodes the structures of all possible join trees for acyclic queries and allows for an efficient dynamic programming algorithm for cost-based optimization. Not only can this representation be viewed as a helpful strategy to guide cost-based optimizers to efficiently find query plans that are likely good, but it can also be helpful for many current theoretically desirable structure-guided approaches that require enumerating or selecting optimal join trees.Succinct Structure Representations for Efficient Query OptimizationZhekai Jiang*, Qichen Wang*, and Christoph Koch(* denotes equal contribution)To appear at SIGMOD ’26: 2026 International Conference on Management of Data, Bengaluru, India, May 2026To be published in Proceedings of the ACM on Management of Data, Vol. 4, No. 3 (SIGMOD), Article 240 (Jun 2026), 27 pagesFull version: arXiv:2603.15465 / EPFL Infoscience 20.500.14299/261601Code repository: https://github.com/epfldata/metaDecompI also extended similar ideas to recursive queries, in, e.g., Datalog and Recursive SQL, and proposed the notion of size bound–adorned datalog which allows us to derive, for the first time, a series of theoretical upper bounds on asymptotic complexity and result sizes of recursively defined relations.Size Bound–Adorned DatalogChristian Fattebert, Zhekai Jiang, Christoph Koch, Reinhard Pichler, and Qichen Wang(Authors ordered alphabetically, as is conventional in theoretical venues)To appear at PODS ’26: 45th Symposium on Principles of Database Systems, Bengaluru, India, May 2026To be published in Proceedings of the ACM on Management of Data, Vol. 4, No. 2 (PODS), Article 97 (May 2026), 27 pagesFull version: arXiv:2603.15425 / EPFL Infoscience 20.500.14299/261600Earlier, during my internship at EPFL, I worked on algorithms to efficiently approximate results of aggregation or rollup queries, based on partially materialized data cubes that contain aggregation results projected to lower dimensions.Aggregation and Exploration of High-Dimensional Data Using the Sudokube Data Cube EngineSachin Basil John, Peter Lindner, Zhekai Jiang, and Christoph KochSIGMOD ’23 (Demo): 2023 International Conference on Management of Data, Seattle, USA, Jun 2023https://doi.org/10.1145/3555041.3589729Code repository: https://github.com/epfldata/sudokubePast work on model-driven software engineering at McGill During my undergraduate study of software engineering at McGill, I worked on model-driven software engineering, especially in the context of test case generation for autonomous vehicles. We designed a system Concretize which automatically generates concrete test scenarios (that can be run directly in simulators) based on high-level specifications by the user in a domain-specific language.Concretize: A Model-Driven Tool for Scenario-Based Autonomous Vehicle TestingJerry Hou-Liu*, Zhekai Jiang*, and Aren A. Babikian(* denotes equal contribution)MODELS ’24 (Demo): ACM/IEEE 27th International Conference on Model Driven Engineering Languages and Systems, Linz,Austria, Sep 2024https://doi.org/10.1145/3652620.3687793Code repository: https://github.com/ArenBabikian/concretizeWe further proposed our vision on a collaborative "scenario catalog" that facilitates sharing and analysis of test cases and results, based on a unified metamodel of test scenarios and related statistics.Towards a Traffic Scenario Catalog for Collaborative Testing of Autonomous VehiclesZhekai Jiang, Oszkaár Semeráth, and Aren A. BabikianSE4ADS ’25: IEEE/ACM 1st International Workshop on Software Engineering for Autonomous Driving Systems, Ottawa, Canada, Apr 2025https://doi.org/10.1109/SE4ADS66461.2025.00015 Teaching & PhDTeaching assistantship / mentorship EPFLMaking intelligent things (CS-358) – Spring 2026, Fall 2025, Spring 2025McGill UniversityLinear algebra and geometry (MATH 133) – Fall 2022, Fall 2021, Fall 2020Programming languages and paradigms (COMP 302) – Winter 2022Introduction to software engineering (ECSE 321) – Fall 2021, Winter 2021 Awards EDIC PhD Fellowship EPFL 2024 Charles Michael Morsson Gold Medal McGill University 2024 Dean's Honour List McGill University 2024 Tomlinson Engagement Award for Mentoring McGill University 2022 Hatch Scholarship in Engineering McGill University 2022 Scholarship of Excellence EPFL 2022 Schull–Yang International Experience Award McGill University 2022 Engineering Class of 1983 Scholarship McGill University 2021 Rio Tinto–Richard Evans International Exchange Award McGill University 2020 John V. Galley Scholarship McGill University 2020