Denis Hirn
Research Assistant
Universität Tübingen, WSI
Lehrstuhl für Datenbanksysteme
Sand 13
72076 Tübingen
Room B312
+49 7071 29-75485
+49 7071 29-5958
denis.hirn@uni-tuebingen.de
0000-0001-7040-1780
Program Committees
- DBPL 2025 (Program Committee, Support),
- SIGMOD 2025 (Program Committee),
- SIGMOD 2024 (Availability and Reproducibility Committee),
- SIGMOD 2023 (Availability and Reproducibility Committee),
- SIGMOD 2022 (Availability Committee)
Open Source Contributions
I regularly contribute to the DuckDB project. I am heavily invested in DuckDB’s CTE implementation, including their parallel execution and decorrelation. My contributions include:
- Recursive CTEs
- Materialized CTEs
- Decorrelation and parallelization (#10357, 17294)
- CTE Behavior Changes and Optimization
The full list of my contributions can be found here: Pull Requests. Also, I regularly supervise student projects that either contribute to DuckDB, use DuckDB, or expand DuckDB’s ecosystem (e.g., DuckDB Plan Visualizer).
Teaching Assistance
Research Supervisor
| 2025: | Matthis Noël | Bachelor Thesis | Execution Visualized: Shareable Plan Visualization for DuckDB based on PEV2 |
| 2025: | Ann-Kathrin Claessens | Master Thesis | From PostgreSQL to DuckDB: Unusual Queries, their Performance, and Readability |
| 2024: | Nico Faden | Bachelor Thesis | Bringing ORDINALITY to DuckDB |
| 2024: | Björn Bamberg | Master Thesis | DuckDB: Improved Support for List Functions |
| 2024: | Robert Stahl | Bachelor Thesis | Extend JSON Path Expressions in DuckDB |
| 2023: | Adrian Müller | Master Thesis | Extending WITH RECURSIVE With Multiple Working Tables |
| 2023: | Alexander Götz | Bachelor Thesis | From PL/pgSQL to C: What Are the Optimizations? |
| 2022: | Phil Elgert | Master Thesis | Creating a Website with a Static Site Generator |
| 2022: | Marcus Huber | Master Thesis | Optimization of PL/pgSQL Translations Using Batching |
| 2022: | Tim Fischer | Master Thesis | ByePy: Compilation of Python to SQL |
| 2021: | Jonatan Braun | Master Thesis | Extend SQLite3 with Support for LATERAL Join |
| 2021: | Tobias Burghardt | Master Thesis | From Recursion To Iteration: Compiling SQL UDFs with Continuations |
Short Biography
- since May 2018: Research Assistant at the Database Systems Chair
- Oct 2013 - Sept 2019: Student of Computer Science at University of Tübingen
Recent Publications
BIRNE: Mixed-paradigm Workload Execution in SQL Engines
DBPL 2025, The 19th International Symposium on Database Programming Languages, June 27th, 2025, Berlin, Germany. doi:10.1145/3735106.3736535
BibTeX Citation
@inproceedings{10.1145/3735106.3736535,
author = {Fischer, Tim and Hirn, Denis},
title = {BIRNE: Mixed-paradigm Workload Execution in SQL Engines},
year = {2025},
isbn = {9798400719196},
publisher = {Association for Computing Machinery},
address = {New York, NY, USA},
url = {https://doi.org/10.1145/3735106.3736535},
doi = {10.1145/3735106.3736535},
booktitle = {Proceedings of the 19th International Symposium on Database Programming Languages},
articleno = {4},
numpages = {11},
keywords = {Compiler, Recursion, SQL},
location = {Berlin, Germany},
series = {DBPL '25}
}
How DuckDB is USING KEY to Unlock Recursive Query Performance
Björn Bamberg • Denis Hirn • Torsten Grust
Proceedings of the 2025 ACM SIGMOD International Conference on Management of Data (SIGMOD'25), June 22–27, 2025, Berlin, Germany. (To be published.)
A Reproducible Tutorial on Reproducibility in Database Systems Research
Tim Fischer • Denis Hirn • Gökhan Kul
Proceedings of 50th Int’l Conference on Very Large Databases (VLDB 2024), AuguLst 26-30, 2024, Guangzhou, China. PVLDB, Volume 17.
SQL Engines Excel at the Execution of Imperative Programs
Tim Fischer • Denis Hirn • Torsten Grust
PVLDB, Volume 17, No. 13: 4696 - 4708, 2024. doi:10.14778/3704965.3704976
BibTeX Citation
@article{10.14778/3704965.3704976,
author = {Fischer, Tim and Hirn, Denis and Grust, Torsten},
title = {SQL Engines Excel at the Execution of Imperative Programs},
year = {2025},
issue_date = {September 2024},
publisher = {VLDB Endowment},
volume = {17},
number = {13},
issn = {2150-8097},
url = {https://doi.org/10.14778/3704965.3704976},
doi = {10.14778/3704965.3704976},
journal = {Proc. VLDB Endow.},
month = feb,
pages = {4696–4708},
numpages = {13}
}
Dear User-Defined Functions, Inlining isn’t working out so great for us. Let’s try batching to make our relationship work. Sincerely, SQL
Kai Franz ☠ • Sam Arch ☠ • Denis Hirn • Torsten Grust • Todd C. Mowry ☠ • Andy Pavlo ☠
(☠ Carnegie Mellon University)
Proceedings of the 14th Conference on Innovative Data Systems Research (CIDR 2024), Chaminade, CA, USA, January 2024.
Data is Data and Control Should be Data, Too—Compiling Iterative Table-valued PL/SQL UDFs into Recursive SQL Code
VLDB 2023 PhD Workshop, co-located with the 49th International Conference on Very Large Data Bases (VLDB 2023), August 28, 2023, Vancouver, Canada
A Fix for the Fixation on Fixpoints
Proceedings of the 13th Conference on Innovative Data Systems Research (CIDR 2023), Amsterdam, The Netherlands, January 2023.
Snakes on a Plan — Compiling Python Functions into Plain SQL Queries
Denis Hirn • Torsten Grust • Tim Fischer
Proceedings of the 41st ACM SIGMOD Int’l Conference on Management of Data (SIGMOD 2022), Philadelphia, PA, USA, June 2022. doi:10.1145/3514221.3520175
BibTeX Citation
@inproceedings{snakes-on-a-plan,
author = {Fischer, Tim and Hirn, Denis and Grust, Torsten},
title = {Snakes on a Plan: Compiling Python Functions into Plain SQL Queries},
year = {2022},
isbn = {9781450392495},
publisher = {Association for Computing Machinery},
address = {New York, NY, USA},
url = {https://doi.org/10.1145/3514221.3520175},
doi = {10.1145/3514221.3520175},
booktitle = {Proceedings of the 2022 International Conference on Management of Data},
pages = {2389–2392},
numpages = {4},
keywords = {SQL, compilation, python, recursion, user-defined functions},
location = {Philadelphia, PA, USA},
series = {SIGMOD '22}
}
Functional Programming on Top of SQL Engines
Tobias Burghardt • Denis Hirn • Torsten Grust
Proceedings of the 24th International Symposium on Practical Aspects of Declarative Languages (PADL 2022), Philadelphia, PA, USA, January 2022. https://doi.org/10.1007/978-3-030-94479-7_5.