Juliusz Sompolski
Staff Software Engineer at Databricks
Amsterdam, North Holland, Netherlands
Summary
🤩
Rockstar🎓
Top SchoolJuliusz Sompolski is a Staff Software Engineer in Amsterdam with 15 years of experience specializing in database engine internals, query execution and performance optimization, currently working on Delta Lake DML and Spark Connect at Databricks. He combines rigorous academic training in mathematics and computer science (top grades from University of Warsaw and VU Amsterdam) with a long-standing competitive-algorithms background, including national-level olympiad finals. His contributions to major open-source projects—Apache Spark, Delta Lake and pyodbc—focus on robust backend improvements, test automation and hard-to-reproduce edge cases like UDT MERGE semantics, deletion vectors and blocking-stream OOM fixes. Previously he drove performance work on Vector/VectorH engines at Actian and led Databricks’ BI Experience and customer performance efforts, bridging low-level engine changes with real-world SQL/ODBC workloads. Colleagues value him for turning formal algorithmic insight into practical, production-grade fixes that surface only under heavy scale or obscure data layouts.
15 years of coding experience
6 years of employment as a software developer
Master of Science (MSc), Computer Science, GPA 9.4/10, Thesis 9.5/10, Master of Science (MSc), Computer Science, GPA 9.4/10, Thesis 9.5/10 at Vrije Universiteit AmsterdamBachelor of Science (BSc), Mathematics, final result: very good, Bachelor of Science (BSc), Mathematics, final result: very good at Uniwersytet WarszawskiThe Academic Secondary School of Nicolaus Copernicus University in Torun
English, Polish, Dutch
Stackoverflow
1reputation
0reached
1answer
0questions
Github Skills (32)
apache-spark10
spark10
delta-lake10
python10
operation10
data-engineering10
testing10
odbc10
database-testing10
mergetool10
java10
scala10
merge10
javas10
mergesort10
Programming languages (7)
Github contributions (5)
databricks/spark-sql-perf
May 2017 - Mar 2018
Role in this project:
Back-end Developer
Back-end DeveloperContributions:16 commits, 25 PRs, 14 pushes in 9 months
Contributions summary:Juliusz primarily focused on improving the performance and functionality of the Spark SQL performance testing framework. They corrected data type discrepancies within the TPCDS table definitions, ensuring data integrity. Furthermore, the user implemented several optimizations, including adding options to customize date formats and the ability to analyze tables by gathering statistics. Additional improvements focused on enhancements to the data generation and benchmark execution, including a fix for blocking streams to prevent OOMs.
apache/spark
Jul 2017 - Oct 2022
Apache Spark - A unified analytics engine for large-scale data processing
Role in this project:Back-end Developer
Back-end DeveloperContributions:410 reviews, 2 commits, 92 PRs in 5 years 4 months
Contributions summary:Juliusz primarily contributed to the Apache Spark project by addressing issues related to the SQL engine, specifically focusing on improving data processing and data source interactions. Their work included documenting the behavior of `saveAsTable` in relation to JDBC sources, unescaping column names in partitioning schemas, and correcting issues with metrics related to joins and aggregations. Furthermore, the user's contributions covered implementing improvements to the reading path in `ReadAheadInputStream`, resolving a 32-bit integer overflow issue in approximate quantile calculations, and improving the documentation.
analyticspythondata-processingsqlapache
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