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Encyclopedia of Database Systems pp 1412–1413Cite as

Execution Skew

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Definition

Execution skew is a phenomenon observed during the parallel evaluation of a database query, in which the concurrent operators exhibit disparate execution times.

Key Points

Execution skew is a phenomenon observed in the parallel evaluation of a database query. It arises when there are imbalances in the execution of the operators running in parallel, resulting in some of the operators running for a longer time than others. The differences in execution times may cause some of the processors to remain idle while others still compute a part of the query. Execution skew can be a consequence of other forms of skew within a query, e.g., data skew, or arise because of temporally unavailable resources that affect the execution speed of a unit of work. The database system can minimize execution skew through the careful allocation of processors to operators and the selection of the appropriate parallel query plan. Execution skew arises in both operator-level parallelism as well as...

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Recommended Reading

  1. Märtens H. A classification of skew effects in parallel database systems. In: Proceedings of the 7th International Euro-Par Conference; 2001, p. 291–300.

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Author information

Authors and Affiliations

  1. Carnegie Mellon University, Pittsburgh, PA, USA

    Nikos Hardavellas & Ippokratis Pandis

  2. Amazon Web Services, Seattle, WA, USA

    Ippokratis Pandis

Authors
  1. Nikos Hardavellas
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  2. Ippokratis Pandis
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Corresponding author

Correspondence to Nikos Hardavellas .

Editor information

Editors and Affiliations

  1. Georgia Institute of Technology College of Computing, Atlanta, GA, USA

    Ling Liu

  2. University of Waterloo School of Computer Science, Waterloo, ON, Canada

    M. Tamer Özsu

Section Editor information

  1. Informatique et Communications, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland

    Anastasia Ailamaki

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© 2018 Springer Science+Business Media, LLC, part of Springer Nature

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Hardavellas, N., Pandis, I. (2018). Execution Skew. In: Liu, L., Özsu, M.T. (eds) Encyclopedia of Database Systems. Springer, New York, NY. https://doi.org/10.1007/978-1-4614-8265-9_1555

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