Analyzing Plan Diagrams of Database Query Optimizers

Analyzing Plan Diagrams of Database Query Optimizers

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

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