Cost Based Query Scrambling for Initial Delays.

Tolga Urhan, Michael J. Franklin, Laurent Amsaleg: Cost Based Query Scrambling for Initial Delays. SIGMOD Conference 1998: 130-141
  author    = {Tolga Urhan and
               Michael J. Franklin and
               Laurent Amsaleg},
  editor    = {Laura M. Haas and
               Ashutosh Tiwary},
  title     = {Cost Based Query Scrambling for Initial Delays},
  booktitle = {SIGMOD 1998, Proceedings ACM SIGMOD International Conference
               on Management of Data, June 2-4, 1998, Seattle, Washington, USA},
  publisher = {ACM Press},
  year      = {1998},
  isbn      = {0-89791-995-5},
  pages     = {130-141},
  ee        = {, db/conf/sigmod/UrhanFA98.html},
  crossref  = {DBLP:conf/sigmod/98},
  bibsource = {DBLP,}


Remote data access from disparate sources across a wide-area network such as the Internet is problematic due to the unpredictable nature of the communications medium and the lack of knowledge about the load and potential delays at remote sites. Traditional, static, query processing approaches break down in this environment because they are unable to adapt in response to unexpected delays. Query scrambling has been proposed to address this problem. Scrambling modifies query execution plans on-the-fly when delays are encountered during runtime. In its original formulation, scrambling was based on simple heuristics, which although providing good performance in many cases, were also shown to be susceptible to problems resulting from bad scrambling decisions. In this paper we address these shortcomings by investigating ways to exploit query optimization technology to aid in making intelligent scrambling choices. We propose three different approaches to using query optimization for scrambling. These approaches vary, for example, in whether they optimize for total work or response-time, and whether they construct partial or complete alternative plans. Using a two-phase randomized query optimizer, a distributed query processing simulator, and a workload derived from queries of the TPC-D benchmark, we evaluate these different approaches and compare their ability to cope with initial delays in accessing remote sources. The results show that cost-based scrambling can effectively hide initial delays, but that in the absence of good predictions of expected delay durations, there are fundamental tradeoffs between risk aversion and effectiveness.

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Laura M. Haas, Ashutosh Tiwary (Eds.): SIGMOD 1998, Proceedings ACM SIGMOD International Conference on Management of Data, June 2-4, 1998, Seattle, Washington, USA. ACM Press 1998, ISBN 0-89791-995-5 BibTeX , SIGMOD Record 27(2), June 1998

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Laurent Amsaleg, Philippe Bonnet, Michael J. Franklin, Anthony Tomasic, Tolga Urhan: Improving Responsiveness for Wide-Area Data Access. IEEE Data Eng. Bull. 20(3): 3-11(1997) BibTeX
Laurent Amsaleg, Michael J. Franklin, Anthony Tomasic, Tolga Urhan: Scrambling Query Plans to Cope With Unexpected Delays. PDIS 1996: 208-219 BibTeX
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Richard L. Cole, Goetz Graefe: Optimization of Dynamic Query Evaluation Plans. SIGMOD Conference 1994: 150-160 BibTeX
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Alberto O. Mendelzon, George A. Mihaila, Tova Milo: Querying the World Wide Web. PDIS 1996: 80-91 BibTeX
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Referenced by

  1. Ron Avnur, Joseph M. Hellerstein: Eddies: Continuously Adaptive Query Processing. SIGMOD Conference 2000: 261-272
  2. Mary Tork Roth, Fatma Ozcan, Laura M. Haas: Cost Models DO Matter: Providing Cost Information for Diverse Data Sources in a Federated System. VLDB 1999: 599-610
  3. Donko Donjerkovic, Raghu Ramakrishnan: Probabilistic Optimization of Top N Queries. VLDB 1999: 411-422
  4. Zachary G. Ives, Daniela Florescu, Marc Friedman, Alon Y. Levy, Daniel S. Weld: An Adaptive Query Execution System for Data Integration. SIGMOD Conference 1999: 299-310
  5. Francis C. Chu, Joseph Y. Halpern, Praveen Seshadri: Least Expected Cost Query Optimization: An Exercise in Utility. PODS 1999: 138-147
  6. Daniela Florescu, Alon Y. Levy, Alberto O. Mendelzon: Database Techniques for the World-Wide Web: A Survey. SIGMOD Record 27(3): 59-74(1998)
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