A Study of moving Selection Down, and Top-Down and Bottom-Up Evaluation Strategies for Logical Queries
Tianzhu Li, Robert R. Korfhage · D-Scholarship@Pitt (University of Pittsburgh) · 1990
Static optimization of logical queries, substantially, is to push selection as far as possible in evaluating the relations of the queries. This paper shows that using Ullman's RGG (Rule/Goal Graph), static optimization for all the situations, non-recursive, recursive, mutually recursive, with some functions included, can be processed intuitively. several possible models of pushing selections down are presented. It is easy to understand and to see how, and how far the selections can be pushed down. Based on this, a recommendation about which of Top-Down and Bottom-Up evaluation strategies should be adopted is presented. This approach is better than other static optimization approach.