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    • 10. 发明授权
    • Cost-based maintenance of materialized views
    • 物质视图的成本维护
    • US6026390A
    • 2000-02-15
    • US890194
    • 1997-07-09
    • Kenneth A. RossDivesh SrivastavaSundararajarao Sudarshan
    • Kenneth A. RossDivesh SrivastavaSundararajarao Sudarshan
    • G06F17/30
    • G06F17/30383G06F17/30312Y10S707/99931Y10S707/99932Y10S707/99933Y10S707/99934Y10S707/99935Y10S707/99936Y10S707/99937
    • A method of incrementally maintaining a first materialized view of data in a database, by means of an additional materialized view, first determines whether a cost in time of incrementally maintaining the first materialized view with the additional materialized view is less than the cost of incrementally maintaining the first materialized view without the additional materialized view. The method creates the additional materialized view only if the cost in time is less therewith. Determining whether the cost of employing an additional materialized view is less includes using an expression directed acyclic graph that corresponds to the first materialized view. Another method of determining whether the cost is less includes pruning an expression directed acyclic graph to produce a single expression tree, and using the single expression tree to determine whether the cost is less. Both the expression directed acyclic graph and the single expression tree contain equivalence nodes. One or more possible materialized views are selected by marking the equivalence nodes, and materializing one or more views corresponding to the marked equivalence nodes. One or more possible materialized views are also selected by determining which of the views, if materialized, would result in a lowest cost of incrementally maintaining the first materialized view. The method is also used to reduce the cost in time of maintaining a first materialized view employed to check an integrity constraint of the database.
    • 通过附加的物化视图来逐步维护数据库中的数据的第一物化视图的方法首先确定用附加物化视图逐步维持第一物化视图的时间成本是否小于增量维护的成本 第一个物化视图没有附加的物化视图。 该方法只有在时间上的成本较低时才创建附加的物化视图。 确定采用附加物化视图的成本是否较小包括使用对应于第一实例化视图的表达式有向无环图。 确定成本是否较小的另一种方法包括修剪表达式非循环图以产生单个表达式树,并使用单个表达式树来确定成本是否较小。 表达式非循环图和单个表达式树都包含等价节点。 通过标记等价节点以及实现对应于标记的等价节点的一个或多个视图来选择一个或多个可能的物化视图。 还可以通过确定哪些视图(如果实现)将导致递增地维持第一实例化视图的最低成本来选择一个或多个可能的物化视图。 该方法还用于降低维护用于检查数据库的完整性约束的第一物化视图的时间成本。