IBM Journal of Research and Development
IBM Skip to main content
  Home     Products & services     Support & downloads     My account  

  Select a country  
Journals Home  
  Systems Journal  
Journal of Research
and Development
    Current Issue  
    Recent Issues  
    Papers in Progress  
    Recent publications  
    Author's Guide  
  Contact Us  
  Related links:  
     IBM Research  

IBM Journal of Research and Development  
Volume 27, Number 5, Page 497 (1983)
Communications Technology
  Full article: arrowPDF   arrowCopyright info


Optimization of Relational Expressions Using A Logical Analogon

by G. A. Blaauw, A. J. W. Duijvestijn, R. A. M. Hartmann
An expression applying to a relational database is optimized by mapping the expression upon set expressions which, in turn, are transformed into logical expressions. These logical expressions then are optimized, taking into account the constraints that are inherent in relational expressions and the costs of those expressions. Subsequently a reverse transformation to relational expressions is applied. The method is developed for the traditional relational operators and is applicable to a variety of cost criteria. Common subexpressions as well as redundant expressions are optimized. A new relational operation "split" is proposed that may be used effectively in an optimized expression. Results obtained with a model for the optimization method are presented.
Related Subjects: Data, structures and accessing; Databases, relational; Optimization