Method and apparatus for analyzing the effect of different execution parameters on the performance of a database query

摘要

A database application re-uses one or more query execution strategies for a given logical query, and saves historical data concerning query execution performance under differing execution parameters. The historical data is analyzed to identify environmental variables and/or imported variables which significantly affect execution performance. Preferably, an auxiliary data structure includes, for each of multiple execution strategies, a respective set of imported and environmental variables and respective average cost measure, such as execution time. An analytical tool compares multiple different strategies to identify imported and/or environmental variables which caused a different strategy to be used, and resultant average cost. Preferably, the tool can also compare variation within the same strategy.