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Encyclopedia of Database Systems pp 2288Cite as

Query Processing

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Synonyms

Query evaluation

Definition

A query processor receives a query, validates it, optimizes it into a procedural dataflow execution plan and executes it to obtain the results of the query.

Key Points

Query processing consists of several phases. In the first phase, the query parser checks whether the query is correctly specified, resolves any names and references, verifies consistency, and performs authorization tests. If the query passes validation, it is converted into an internal representation that can be easily processed by the subsequent phases. Then, the query rewrite module, or rewriter, simplifies the query and transforms it into an equivalent form by carrying out a number of optimizations that do not depend on the physical state of the system, such as view expansion and logical rewriting of predicates. These initial phases rely only on data and metadata in the system catalog.

Next, the query optimizertransforms the internal query representation into an efficient query...

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Recommended Reading

  1. Graefe G. Query evaluation techniques for large databases. ACM Comput. Surv., 25(2):73–170, 1993.

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  2. Haas L.M., Freytag J.C., Lohman G.M., and Pirahesh H. Extensible query processing in starburst. In Proc. ACM SIGMOD Int. Conf. on Management of Data, 1989, pp. 377–388.

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  3. Hellerstein J.M., Stonebraker M., and Hamilton J. Architecture of a database system. Foundations and Trends in Databases, vol. 1(2), 2007.

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Author information

Authors and Affiliations

  1. University of Ioannina, Ioannina, Greece

    Evaggelia Pitoura

Authors
  1. Evaggelia Pitoura
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Editor information

Editors and Affiliations

  1. College of Computing, Georgia Institute of Technology, 266 Ferst Drive, 30332-0765, Atlanta, GA, USA

    LING LIU (Professor) (Professor)

  2. Database Research Group David R. Cheriton School of Computer Science, University of Waterloo, 200 University Avenue West, N2L 3G1, Waterloo, ON, Canada

    M. TAMER ÖZSU (Professor and Director, University Research Chair) (Professor and Director, University Research Chair)

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© 2009 Springer Science+Business Media, LLC

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Pitoura, E. (2009). Query Processing. In: LIU, L., ÖZSU, M.T. (eds) Encyclopedia of Database Systems. Springer, Boston, MA. https://doi.org/10.1007/978-0-387-39940-9_860

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