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Exact Cardinality Query Optimization for Optimizer Testing

Exact Cardinality Query Optimization for Optimizer Testing,Proceedings of The Vldb Endowment,Surajit Chaudhuri,Vivek R. Narasayya,Ravishankar Ramamurt

Exact Cardinality Query Optimization for Optimizer Testing   (Citations: 1)
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The accuracy of cardinality estimates is crucial for obtaining a good query execution plan. Today"s optimizers make several simplifying assumptions during cardinality estimation that can lead to large errors and hence poor plans. In a scenario such as query optimizer testing it is very desirable to obtain the "best" plan, i.e., the plan produced when the cardinality of each relevant expression is exact. Such a plan serves as a baseline against which plans produced by using the existing cardinality estimation module in the query optimizer can be compared. However, obtaining all exact cardinalities by executing appropriate sub- expressions can be prohibitively expensive. In this paper, we present a set of techniques that makes exact cardinality query optimization a viable option for a significantly larger set of queries than previously possible. We have implemented this functionality in Microsoft SQL Server and we present results using the TPC-H benchmark queries that demonstrate their effectiveness.
Journal: Proceedings of The Vldb Endowment - PVLDB , vol. 2, no. 1, pp. 994-1005, 2009
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