I am a developer relations advocate at DuckDB Labs, the company behind DuckDB, an in-process analytical database management system. As a devrel, I perform a wide range of activities, including:

I was also running DuckDB’s social media sites and handled the DuckDB merchandise.

Previously, I spent a decade on academia. I obtained my PhD in software engineering at the Critical Systems Research group of BME in Budapest. I did a 3-year stint as a post-doctoral researcher at the Database Architectures group of CWI in Amsterdam. My research focused on graph processing, including creating standard graph processing benchmarks for the Linked Data Benchmark Council.

GitHub – Twitter – LinkedIn – Stack Overflow – Google Scholar – DBLP

News

Sep: I gave a talk on DuckDB at code.talks in Hamburg.
Aug: I was a co-organizer of DuckCon #5, held in Seattle.
Jun: I gave talks at the Budapest Data+ML Forum and GOTO Amsterdam.
May: I keynoted the GraphSys workshop at ICPE 2024 in London. My slide deck is available.

For older items, see the news archive.

Notes

Installing tidyverse on macOS

The tidyverse R package cannot be installed on macOS because one of its dependencies, ragg fails to compile with the following error: clang++ -std=gnu++17 -I"/opt/homebrew/Cellar/r/4.4.1/lib/R/include" -DNDEBUG -I./agg/include -I/opt/homebrew/opt/freetype/include/freetype2 -I/opt/homebrew/opt/libpng/include/libpng16 -I/opt/homebrew/Cellar/libtiff/4.6.0/include -I/opt/homebrew/opt/zstd/include -I/opt/homebrew/Cellar/xz/5.6.2/include -I/opt/homebrew/Cellar/jpeg-turbo/3.0.3/include -I'/opt/homebrew/lib/R/4.4/site-library/systemfonts/include' -I'/opt/homebrew/lib/R/4.4/site-library/textshaping/include' -I/opt/homebrew/opt/gettext/include -I/opt/homebrew/opt/readline/include -I/opt/homebrew/opt/xz/include -I/opt/homebrew/include -fPIC -g -O2 -Wall -pedantic -fdiagnostics-color=always -c agg/src/agg_vcgen_stroke.cpp -o agg/src/agg_vcgen_stroke.o agg/src/agg_font_freetype.cpp:116:18: warning: variable 'len' set but not used [-Wunused-but-set-variable] unsigned len = 0; ^ agg/src/agg_font_freetype.cpp:182:35: error: assigning to 'char *' from 'unsigned char *' converts between pointers to integer types where one is of the unique plain 'char' type and the other is not tags = outline....

Setting up a MacBook for Presentations

Overview A recurring task in my day job is to organize technical conferences (most recently, DuckCon #4 and #5), and to run the event from my laptop. To this end, I configure my laptop to ensure the best experience for both speakers and attendees. Most of the events I organize are free, so there is a limited budget available. Additionally, there is a limited amount of time prepare. For example, it is not possible to conduct rehearsals with speakers....

macOS command line tricks

Make git beep upon failed push Motivation: When I issue a git push command, I immediately navigate away from the terminal. Therefore, if the command fails due to the remote rejecting it after a second, I do not see this and assume that the push was successful. To avoid this, we’ll configure the shell so when git push fails, it gives a small beep sound. To do so, follow these steps:...

DuckDB workshop

Setup DuckDB installation site duckman: DuckDB Version Manager railway.ipynb Jupyter notebook Weather data set Source: Visual Crossing Weather wget https://blobs.duckdb.org/data/amsterdam-weather.csv Railway data set Source: Rijden de Treinen wget https://blobs.duckdb.org/nl-railway/stations-2022-01.csv wget https://blobs.duckdb.org/nl-railway/tariff-distances-2022-01.csv wget https://blobs.duckdb.org/nl-railway/services-2019.csv.gz wget https://blobs.duckdb.org/nl-railway/services-2020.csv.gz wget https://blobs.duckdb.org/nl-railway/services-2021.csv.gz wget https://blobs.duckdb.org/nl-railway/services-2022.csv.gz wget https://blobs.duckdb.org/nl-railway/services-2023.csv.gz wget https://blobs.duckdb.org/nl-railway/services-2024-01.csv.gz wget https://blobs.duckdb.org/nl-railway/services-2024-02.csv.gz wget https://blobs.duckdb.org/nl-railway/services-2024-03.csv.gz wget https://blobs.duckdb.org/nl-railway/services-2024-04.csv.gz VS Code hotkey Define keyboard shortcut Ctrl + Enter for executing selection in terminal To use the same editor (VS Code) and the same keyboard shortcut (Ctrl + Enter) to run the active line / selected piece of code (for CLI) or the active cell (for Python notebooks), add the CLI hotkey as follows:...

Using the Aztec Code on an iPhone to enter the gates at Dutch train stations

TL;DR: To prevent your iPhone from switching to Apple Pay at train station gates when scanning your ticket’s code, use Guided Access mode. This can be turned on in the accessibility settings and activated by triple-clicking the side button of your phone. Recently, when travelling to FOSDEM from Amsterdam to Brussels via railway, I ran into the following problem. The Aztec Code for my train was saved on my iPhone. When I pulled out the phone to scan it at the entrance gates of Amsterdam Centraal, my phone kept opening the wallet for Apple Pay, making the Aztec Code no longer visible....

Publications at VLDB 2023

I co-authored the following papers, to be presented at VLDB 2023 and its satellite events. These papers capture the work on the new and updated benchmarks of the Linked Data Benchmark Council (LDBC), as well as LDBC’s organizational restucturing. Additionally, an initial DuckDB-based prototype of the SQL/PGQ language extension was accepted at the demo track. VLDB 2023 main track – G. Szárnyas et al.: The LDBC Social Network Benchmark: Business Intelligence workload [slide deck] TPCTC 2023 – G....

E-bike rental options in Amsterdam

Recently, I had a few family members visiting me in Amsterdam and I wanted to show them around the Dutch countryside. To give us a larger radius – and put towns like Marken, Zaandam, and Naarden comfortably within reach – I decided to rent e-bikes. In this post, I document my findings about the available options and the bikes I rented. Note that my lessons learnt are valid as of summer 2022 and are likely to change in the future....

Self-joins

Introduction A self-join is a relational join operation which joins a table to itself, typically based on equivalence predicates. For example, given the table \(\mathsf{knows}(\mathsf{person1\_id}, \mathsf{person2\_id})\), representing a social graph where people know each other, and aliases of this table \(\mathsf{knows1}, \mathsf{knows2}, \ldots\), take the following query: SELECT knows1.person1_id AS pA, knows1.person2_id AS pB, knows2.person2_id AS pC FROM knows knows1 JOIN knows knows2 ON knows2.person1_id = knows1.person2_id; The query specifies a self-join on the \(\mathsf{knows}\) table, \(\mathsf{knows1} \bowtie \mathsf{knows2}\), and produces two-hop paths in the social graph....

Graph query languages

The maze of graph query languages can be difficult as there are a number of similarly named languages with subtle differences. This document contains a very brief description of popular graph query languages. Languages Property graphs A number of languages exist for defining graph queries over property graphs. Here’s a list of 10 popular languages: Cypher: The declarative graph query language used by the Neo4j graph database. Cypher popularized the ASCII art syntax for defining graph patterns....

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