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1. 发明授权

US08046354B2 Method and apparatus for re-evaluating execution strategy for a database query 失效
标题翻译：重新评估数据库查询执行策略的方法和装置
公开(公告)号：US08046354B2
公开(公告)日：2011-10-25
申请号：US10955737
申请日：2004-09-30
申请人： Paul Reuben Day , Lee William Jameson , Roger Alan Mittelstadt , Brian Robert Muras
发明人： Paul Reuben Day , Lee William Jameson , Roger Alan Mittelstadt , Brian Robert Muras
IPC分类号： G06F17/30
CPC分类号： G06F17/30463 , G06F17/30471 , G06F17/30474
摘要： A query facility for database queries saves and re-uses query execution strategies, and automatically detects that a strategy should be re-optimized as a result of changes to an indexed variable value. Preferably, the number of records evaluated and selected by the index value condition is dynamically monitored during execution, and an alternative query strategy is initiated when this number appears to be out of proportion to expectations. In an exemplary embodiment, an indexed search strategy is changed to a table scan strategy (or vice versa) as a result of a change to the number of records eliminated by the indexed value, although other examples are possible. Preferably, the query engine initiates an alternative search strategy and concurrently continues to execute the original search strategy as separate threads. Search results are obtained from whichever thread completes first.
摘要翻译：用于数据库查询的查询功能保存并重新使用查询执行策略，并自动检测到由于对索引变量值的更改，策略应重新优化。优选地，在执行期间动态地监视由索引值条件评估和选择的记录的数量，并且当该数量看起来与期望不成比例时，开始替代查询策略。在示例性实施例中，作为由索引值消除的记录数的改变的结果，索引的搜索策略被改变为表扫描策略（或反之亦然），尽管其他示例是可能的。优选地，查询引擎发起替代搜索策略并且同时继续执行原始搜索策略作为单独的线程。搜索结果从无论哪个线程首先完成。

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