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Supporting Views in Data Stream Management Systems

机译:数据流管理系统中的支持视图

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In relational database management systems, views supplement basic query constructs to cope with the demand for "higher-level" views of data. Moreover, in traditional query optimization, answering a query using a set of existing materialized views can yield a more efficient query execution plan. Due to their effectiveness, views are attractive to data stream management systems. In order to support views over streams, a data stream management system should employ a closed (or composable) continuous query language. A closed query language is a language in which query inputs and outputs are interpreted in the same way, hence allowing query composition.rnThis article introduces the Synchronized SQL (or SyncSQL) query language that defines a data stream as a sequence of modify operations against a relation. SyncSQL enables query composition through the unified interpretation of query inputs and outputs. An important issue in continuous queries over data streams is the frequency by which the answer gets refreshed and the conditions that trigger the refresh. Coarser periodic refresh requirements are typically expressed as sliding windows. In this article, the sliding window approach is generalized by introducing the synchronization principle that empowers SyncSQL with a formal mechanism to express queries with arbitraryrnrefresh conditions. After introducing the semantics and syntax, we lay the algebraic foundation for SyncSQL and propose a query-matching algorithm for deciding containment of SyncSQL expressions. Then, the article introduces the Nile-SyncSQL prototype to support SyncSQL queries. Nile-SyncSQL employs a pipelined incremental evaluation paradigm in which the query pipeline consists of a set of differential operators. A cost model is developed to estimate the cost of SyncSQL query execution pipelines and to choose the best execution plan from a set of different plans for the same query. An experimental study is conducted to evaluate the performance of Nile-SyncSQL. The experimental results illustrate the effectiveness of Nile-SyncSQL and the significant performance gains when views are enabled in data stream management systems.
机译:在关系数据库管理系统中,视图补充了基本的查询构造,以应对对数据“高级”视图的需求。此外,在传统查询优化中,使用一组现有的实体化视图回答查询可以产生更有效的查询执行计划。由于其有效性,视图对于数据流管理系统具有吸引力。为了支持流视图,数据流管理系统应采用封闭(或可组合)的连续查询语言。封闭查询语言是一种以相同方式解释查询输入和输出的语言,因此允许查询组合。rn本文介绍了同步SQL(或SyncSQL)查询语言,该语言将数据流定义为针对数据流的一系列修改操作。关系。 SyncSQL通过统一解释查询输入和输出来启用查询组合。连续查询数据流中的一个重要问题是刷新答案的频率和触发刷新的条件。较粗的定期刷新要求通常表示为滑动窗口。在本文中,通过引入同步原理来概括滑动窗口方法,该同步原理使SyncSQL具有一种正式的机制,可以使用任意刷新条件来表达查询。在介绍了语义和语法之后,我们为SyncSQL奠定了代数基础,并提出了一种查询匹配算法来确定SyncSQL表达式的包含性。然后,本文介绍了Nile-SyncSQL原型以支持SyncSQL查询。 Nile-SyncSQL采用流水线式增量评估范式,其中查询管道由一组差分运算符组成。开发成本模型来估计SyncSQL查询执行管道的成本,并从针对同一查询的一组不同计划中选择最佳执行计划。进行了一项实验研究,以评估Nile-SyncSQL的性能。实验结果说明了Nile-SyncSQL的有效性以及在数据流管理系统中启用视图时的显着性能提升。

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