Reference Work Entry

Encyclopedia of Database Systems

pp 2900-2905

System R (R*) Optimizer

  • Mouna KacimiAffiliated withMax-Planck Institute for Informatics, Saarbrücken
  • , Thomas NeumannAffiliated withMax-Planck Institute for Informatics, Saarbrücken


The System R Optimizer is the cost-based query optimizer of System R. It pioneered several optimization techniques, including using dynamic programming for bottom-up join tree construction, and the concept of interesting orderings for exploiting ordering in intermediate results. Later, it was generalized for distributed database systems in System R*.

Historical Background

System R is a database management system based on a relational data model that was proposed by E. F. Codd [4] in 1970. The system offers data independence by providing a high-level user interface through which the end user deals with data content rather than the underlying storage structures. In other words, users do not need to know how the tuples are physically stored and which access paths are available to write queries. Thus, data storage structures may change over time without users being aware of it, providing a high level of data independence and user productivity. Moreove ...

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