Analyzing Plan Diagrams of Database Query Optimizers

Analyzing Plan Diagrams of Database Query Optimizers

Abstract. This report concentrates on the visualization and analysis of the behavior of query optimizers. In the paper [6] ”Analyzing Plan Diagrams of Database Query Optimizers” the authors visualize the query plans and corresponding estimated costs of a SQL-query with variable parameters in one- or two-dimensional selectivity spaces. Therefore, they introduce Plan and Cost Diagrams. The authors show that the number of query plans of each tested commercial database is surprisingly high. Moreover, they determine a non-motivated fragmentation of the Plan Diagrams. To improve this situation the authors introduce Reduced Plan Diagrams which decrease the number of query plans by summarizing the query plans of Plan Diagrams with limited additional estimated costs. Finally, the authors state that the assumptions of Parametric Query Optimization (PQO) do not hold in practice. They suggest the use of Reduced Plan Diagrams for PQO. [6]

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