Prof. Dr. Felix Naumann

Sebastian Kruse

former member

Research Interests

  • Data profiling
  • Distributed systems
  • Map/Reduce frameworks
  • Query optimization
  • Cross-platform/polyglot data processing



Master's Theses

  • Estimating Metadata of Query Results using Histograms (Cathleen Ramson, 2014)
  • Quicker Ways of Doing Fewer Things: Improved Index Structures and Algorithms for Data Profiling (Jakob Zwiener, 2015)
  • Methods of Denial Constraint Discovery (Tobias Bleifuß, 2016)
  • Optimizing Cross-Platform Iterations on 
    the Rheem Platform (Jonas Kemper, ongoing)


Master Projects

Bachelor Projects

Guest Lectures

Professional Activities



Efficient Denial Constraint Discovery with Hydra

Bleifuß, Tobias; Kruse, Sebastian; Naumann, Felix in Proceedings of the VLDB Endowment (PVLDB) 2017 .

Denial constraints (DCs) are a generalization of many other integrity constraints (ICs) widely used in databases, such as key constraints, functional dependencies, or order dependencies. Therefore, they can serve as a unified reasoning framework for all of these ICs and express business rules that cannot be expressed by the more restrictive IC types. The process of formulating DCs by hand is difficult, because it requires not only domain expertise but also database knowledge, and due to DCs' inherent complexity, this process is tedious and error-prone. Hence, an automatic DC discovery is highly desirable: we search for all valid denial constraints in a given database instance. However, due to the large search space, the problem of DC discovery is computationally expensive. We propose a new algorithm Hydra, which overcomes the quadratic runtime complexity in the number of tuples of state-of-the-art DC discovery methods. The new algorithm's experimentally determined runtime grows only linearly in the number of tuples. This results in a speedup by orders of magnitude, especially for datasets with a large number of tuples. Hydra can deliver results in a matter of seconds that to date took hours to compute.
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