Encyclopedia of Database Systems

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

Evaluation of Relational Operators

  • Jingren Zhou
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_154

Synonyms

Implementation of database operators (joins, group by, etc.); Query evaluation; Query processing

Definition

A query usually consists of several relational operators. The corresponding physical query plan is composed of several physical operators. Generally speaking, a physical operator is an implementation of a relational operator. For each relational operator, there are several alternative algorithms (physical operators) for its implementation, and there is no universally superior one. So choosing physical operators wisely is crucial for query performance. Which physical operator is the best depends on several factors, such as the sizes of the input relations, the existing sorting orders of the input relations, the existing indexes/materialized views, the buffer replacement policy, the size of the available buffer pool, etc.

Historical Background

The relational operators serve as the building blocks for query processing. Their implementation techniques have been extensively...

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Recommended Reading

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    Graefe G. Query evaluation techniques for large databases. ACM Comput Surv. 1993;25(2):73–170.CrossRefGoogle Scholar
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    Mishra P, Eich MH. Join processing in relational databases. ACM Comput Surv. 1992;24(1):63–113.CrossRefGoogle Scholar
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    Ramakrishnan R, Gehrke J. Database management systems. New York: McGraw-Hill; 2002.zbMATHGoogle Scholar
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    Selinger P.G., Astrahan M.M., Chamberlin D.D., Lorie R.A., and Price T.G. Access path selection in a relational database management system. In: Proceedings of the ACM SIGMOD International Conference on Management of Data; 1979. p. 23–34.Google Scholar

Copyright information

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

Authors and Affiliations

  1. 1.Alibaba GroupHangzhouChina

Section editors and affiliations

  • Evaggelia Pitoura
    • 1
  1. 1.Department of Computer Science and EngineeringUniversity of IoanninaIoanninaGreece