Dynamic distributed query processing techniques

  • Authors:

  • P. Bodorik;J. S. Riordon;C. Jacob

  • Affiliations:

  • School of Computer Science, Technical University of Nova Scotia, P.O. Box 1000, Halifax, NS, B3J 2X4, Canada;Department of Systems and Computer Engineering, Carleton University, Ottawa, Ontario, K1S 5B6, Canada;Bell Northern Research, P.O. Box 3511, Postal Station C, Ottawa, K1Y 4H7, Canada

  • Venue:
  • CSC '89 Proceedings of the 17th conference on ACM Annual Computer Science Conference
  • Year:
  • 1989

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Abstract

As optimization of strategies to process queries in a Distributed DataBase (DDB) uses various techniques to estimate the sizes of partial results and other parameters pertaining to the distributed environment, if these estimates are inaccurate the strategies may be far from optimal. Dynamic query execution, which may be used to alleviate this problem, is examined in this paper. Execution of a strategy is assumed to proceed through three phases: (i) monitoring phase in which processors monitor the progress of the strategy execution; (ii) decision making phase in which they may decide to correct the current strategy because it is not optimal due to inaccurate estimates used in its formulation; and (iii) corrective phase in which the current strategy is aborted and a new, corrective strategy is initiated. Methods applicable to each phase and their integration is examined in detail in terms of overhead, complexity and accuracy of information used in correcting a strategy.