Database & AI Systems Researcher

Jie Liu

Final-year Ph.D. candidate in Computer Science and Engineering at the University of Michigan
Advised by Barzan Mozafari · Database Research Group
Microsoft Applied Sciences Group · Research Intern, Summer 2026

I build efficient and reliable AI & data systems. My research sits at the intersection of database systems, AI systems, and automated optimization. Across my work, I combine large language models, program synthesis, execution feedback, measurement, and verification to explore larger optimization spaces while keeping the resulting systems reliable—from SQL queries and data pipelines to long-context language models.

Before Michigan, I completed my M.Phil. and B.S. at The Chinese University of Hong Kong, where I worked on approximate maximum inner-product search.

Ph.D. expected August 2026 · Available full-time October 29, 2026 · Seeking Research Engineer, Applied Scientist, and systems roles

Portrait of Jie Liu

Selected Research

A research program around expanding the optimization space while keeping learned or synthesized decisions measurable and reliable.

DAGSmith

SQL Pipelines · LLMs · Systems

Dependency-aware rewriting for dbt-style SQL pipelines · under review

Modern analytics are DAGs of dependent SQL transformations, but optimizers usually reason about one query at a time. DAGSmith optimizes the whole pipeline, combining dependency-aware targeting and LLM-guided rewriting with materialization and scheduling decisions.

67.7% lower recurring compute cost on Tuva

GenRewrite

SQL · LLMs · Verification

Query rewriting via large language models · SIGMOD 2026

GenRewrite lets LLMs propose whole-query transformations beyond predefined rewrite rules, then places them inside a feedback-driven system with reusable natural-language optimization knowledge, counterexample-guided repair, and correctness/performance gates.

25 / 99 TPC-DS queries with ≥2× speedup

SlabCity

Program Synthesis · SQL

Whole-query optimization using program synthesis · VLDB 2023

Instead of applying a fixed library of rewrite rules, SlabCity directly searches for equivalent, faster SQL programs. Query dataflows guide synthesis, while testing, counterexamples, and verification prune incorrect candidates.

104× maximum observed rewrite speedup

RenderLM

Long Context · Multimodal · ML Systems

Optical context compression for long-context language models · Microsoft ASG, 2026

At Microsoft Applied Sciences Group, I studied how to carry long documents through compact visual representations rather than expensive text tokens. The project focused on learnable rendering, failure analysis, and separating reading from retrieval under aggressive compression.

Project details shown at a high level; no internal materials are linked.

Match in text.
Carry in pixels.
Decompress selectively.

Publications

Google Scholar ↗
  1. DAGSmith: Dependency-Aware Rewriting for dbt-Style SQL Pipelines
    Jie Liu, Lin Ma, Barzan Mozafari.
    Under review.
  2. GenRewrite: Query Rewriting via Large Language Models
    Jie Liu, Barzan Mozafari.
    ACM SIGMOD International Conference on Management of Data, 2026.
  3. SlabCity: Whole-Query Optimization using Program Synthesis
    Rui Dong*, Jie Liu*, Yuxuan Zhu, Cong Yan, Barzan Mozafari, Xinyu Wang.
    Proceedings of the VLDB Endowment, 2023.
  4. Understanding and Improving Proximity Graph based Maximum Inner Product Search
    Jie Liu*, Xiao Yan*, Xinyan Dai, Zhirong Li, James Cheng, Ming-Chang Yang.
    AAAI Conference on Artificial Intelligence, 2020. [code]
  5. Norm-Explicit Quantization: Improving Vector Quantization for Maximum Inner Product Search
    Xinyan Dai*, Xiao Yan*, Kelvin K. W. Ng, Jie Liu, James Cheng.
    AAAI Conference on Artificial Intelligence, 2020 (Oral). [code]
  6. A General and Efficient Querying Method for Learning to Hash
    Jinfeng Li, Xiao Yan, Jian Zhang, An Xu, James Cheng, Jie Liu, Kelvin K. W. Ng, Ti-chung Cheng.
    ACM SIGMOD International Conference on Management of Data, 2018. [code]

* Equal contribution.