文章基本信息

标题：A Study On Query Optimization for Federated Database Systems
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作者：Xinhua Xu
期刊名称：Computer and Information Science
印刷版ISSN：1913-8989
电子版ISSN：1913-8997
出版年度：2009
卷号：2
期号：1
页码：115
DOI：10.5539/cis.v2n1P115
语种：English
出版社：Canadian Center of Science and Education
摘要：Normal 0 7.8 ? 0 2 false false false MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:????; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} In this paper, we explore the design space for a query optimizer in this environment and demonstrate the need for decoupling various aspects of the optimization process. We present minimum-communication decoupled variants of various query optimization techniques, and discuss trade-offs in their performance in this scenario. We have implemented these techniques in the Cohera federated database system and our experimental results, somewhat surprisingly, 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 aggressive algorithms are required otherwise.