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《清华大学学报》2013,(6):618-628
Performance predictions for database queries allow service providers to determine what resources are needed to ensure their performance. Cost-based or rule-based approaches have been proposed to optimize database query execution plans. However, Virtual Machine (VM)-based database services have little or no sharing of resources or interactions between applications hosted on shared infrastructures. Neither providers nor users have the right combination of visibility/access/expertise to perform proper tuning and provisioning. This paper presents a performance prediction model for query execution time estimates based on the query complexity for various data sizes. The user query execution time is a combination of five basic operator complexities: O(1), O(log(n)), O(n), O(nlog(n)), and O(n2). Moreover, tests indicate that not all queries are equally important for performance prediction. As such, this paper illustrates a performance-sensitive query locating process on three benchmarks: RUBiS, RUBBoS, and TPC-W. A key observation is that performance-sensitive queries are only a small proportion (20%) of the application query set. Evaluation of the performance model on the TPC-W benchmark shows that the query complexity in a real life scenario has an average prediction error rate of less than 10% which demonstrates the effectiveness of this predictive model. 相似文献
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产业集群是指在特定区域中,具有竞争与合作关系,且在地理上集中,有交互关联性的企业、专业化供应商、服务供应商、金融机构、相关产业的厂商及其他相关机构等组成的群体。在经济全球化的背景下,区域竞争优势的获取越来越依赖于国家或区域内具有产业属性和地理集中特性的产业集群的互动。 相似文献
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随着Web、通信和娱乐领域的多方面融合,无论是从设备、服务还是应用软件的角度而言,终端用户和市场需求都在迫使多方面发生变革和改变,包括“服务供应商”定义的演进、他们开发和提供的产品与服务以及这些产品与服务消费方式背后的商业模式的变化等。一个明显的趋势是,产品、服务和消费者与设备制造商、媒体和娱乐公司、通信服务供应商以及互联网/Web2.0供应商的传统界限正在逐渐模糊,在某些市场中,甚至正在消失,而市场正日趋融合。 相似文献
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