Abstract: The invention relates to a method of determining the performance of an optimizer program arranged to generate a plan. The method generally comprises the steps of executing the optimizer utilising at least one test case to derive a pre-variation plan; executing the pre-variation plan to generate a first output; varying a strategy of the optimizer program; executing the varied optimizer program utilising the at least one test case to derive a post-variation plan; and executing the post-variation plan to generate a second output. The outputs are then grouped according to at least one element of the plans to assess the performance of the optimizer.

Abstract: Deriving join cost demographics for a binary join, i.e., a join between two relations each having a join column, includes using a correlation factor related to the ratio of unique join column values stored in each of a plurality of units of storage to the total number of unique values in the join column.

Abstract: The invention relates to a method of determining the performance of an optimizer program arranged to generate a plan. The method generally comprises the steps of executing the optimizer utilising at least one test case to derive a pre-variation plan; executing the pre-variation plan to generate a first output; varying a strategy of the optimizer program; executing the varied optimizer program utilising the at least one test case to derive a post-variation plan; and executing the post-variation plan to generate a second output. The outputs are then grouped according to at least one element of the plans to assess the performance of the optimizer.

Abstract: A method, database system, and computer program are disclosed for optimized costing. The method includes identifying a join that identifies a first table and a second table. The method further includes determining an optimized cost of reading the first table. If the number of unique first table values is greater than the number of unique second table values, the number of instances where a unique first table value matches a unique second table value is returned. Otherwise, the number of unique first table values is returned. The method further includes determining an optimized cost of reading the second table. The optimized cost of reading the second table includes the number of unique second table values. The method also includes summing the optimized cost of reading the first table and the optimized cost of reading the second table.