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Execution Skew

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

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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...


  • Operation-level Parallelism
  • Parallel Query Plan
  • Parallel Database Systems
  • Care Allocation
  • Skewed Data

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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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Correspondence to Nikos Hardavellas .

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Hardavellas, N., Pandis, I. (2016). Execution Skew. In: Liu, L., Özsu, M. (eds) Encyclopedia of Database Systems. Springer, New York, NY.

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  • Publisher Name: Springer, New York, NY

  • Online ISBN: 978-1-4899-7993-3

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