Huanchen Zhang, who earned his Ph.D. from the School of Computer Science in 2020, has won the 2021 ACM SIGMOD Jim Gray Dissertation Award, which recognizes the previous year's best dissertation in the database field.

His thesis, "Memory-Efficient Search Trees for Database Management Systems," developed new methods for reducing the memory overhead of search trees. Huanchen's thesis advisers were Computer Science Department faculty members Andy Pavlo and David Andersen. Pavlo won the same award in 2014 for the dissertation he completed at Brown University.

Huanchen's dissertation described a viable key compression method for any tree-based data structure. He developed novel methods for reducing the memory footprint of in-memory index structures without sacrificing performance for the former. His work adapted previously developed methods from information theory and algorithms research and showed how to make them usable in real systems.

Now an assistant professor at Tsinghua University, Huanchen is the second CMU Ph.D. student to win the award in the last three years. CMU students or faculty have won the award four times since it was introduced in 2006.