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US07987178B2 Automatically determining optimization frequencies of queries with parameter markers 失效
使用参数标记自动确定查询的优化频率

Automatically determining optimization frequencies of queries with parameter markers
Abstract:
A method and system for automatically determining optimization frequencies of queries having one or more parameter markers. Execution plans for a query are generated and each plan is associated with one or more bind value sets. An optimization frequency is selected based on differences between pairs of execution costs where one execution cost of a pair is a cost of executing the query with a bind value set via a first execution plan and the other execution cost of the pair is a cost of optimally executing the query with the bind value set via a second execution plan. The differences are based on maximum selectivity or cardinality distances associated with the bind value sets. If none of the differences exceeds a predefined value, the query is optimized once. If at least one of the differences exceeds the predefined value, the query is reoptimized each time the query is executed.
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