Encyclopedia of Database Systems

2018 Edition
| Editors: Ling Liu, M. Tamer Özsu

Intra-query Parallelism

  • Nikos HardavellasEmail author
  • Ippokratis Pandis
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_1557


Query parallelism


Intra-query parallelism is a form of parallelism in the evaluation of database queries, in which a single query is decomposed into smaller tasks that execute concurrently on multiple processors.

Key Points

Intra-query parallelism is achieved when several processors cooperate in the execution of a single query to improve the query’;s response time. Intra-query parallelism is orthogonal to inter-query parallelism, in which multiple independent requests execute concurrently on several processors to improve the overall system throughput.

There exist two forms of intra-query parallelism: operator-level parallelism and intra-operator parallelism. Operator-level parallelism is obtained by executing concurrently several operators of the same query. For example, consider a simple query that consists of a scan operator and an aggregation. The scan operator uses a selection condition to filter tuples. The aggregation calculates some statistics over all...

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Recommended Reading

  1. 1.
    DeWitt DJ, Gray J. Parallel database systems: the future of high-performance database computing. Commun ACM. 1992;35(6):85–98.CrossRefGoogle Scholar
  2. 2.
    Graefe G.. Encapsulation of parallelism in the volcano query processing system. In: Proceedings of the ACM SIGMOD International Conference on Management of Data; 1990. p. 102–11.Google Scholar

Copyright information

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

Authors and Affiliations

  1. 1.Carnegie Mellon UniversityPittsburghUSA
  2. 2.Amazon Web ServicesSeattleUSA

Section editors and affiliations

  • Anastasia Ailamaki
    • 1
  1. 1.Informatique et CommunicationsEcole Polytechnique Fédérale de LausanneLausanneSwitzerland