期刊名称：International Journal of Computer Science Issues
印刷版ISSN：1694-0784
电子版ISSN：1694-0814
出版年度：2011
卷号：8
期号：4
出版社：IJCSI Press
摘要：Query optimization in distributed databases explicitly needed in many aspects of the optimization process, often making it imperative for the optimizer to consult underlying data sources while doing cost based optimization. This is not only increases the cost of optimization, but also changes the trade-offs involved in the optimization process significantly. The leading cost in this optimization process is the "cost of costing" that traditionally has been considered insignificant. The optimizer can only afford a few rounds of messages to the under- lying data sources and hence the optimization techniques in this environment must be geared toward gathering all the required cost information with minimal communication. In this paper, we explore the design and search space for a query optimizer in distributed environment and demonstrate the need for this optimization approach in various aspects of the optimization process. This work present minimumcommunication cost query cost variants of various query optimization techniques, and discuss tradeoffs in their performance in the present development. We have implemented a novel optimization approach in the distributed database environment, somewhat unexpectedly, indicate that a simple two-phase optimization scheme performs fairly well as long as the physical database design is known to the optimizer, though more determined algorithms are required.
关键词：Query Optimization; Query Optimization approach; Query processing in DDBMS
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