Adapting materialized views after redefinitions: techniques and a performance study |
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| Affiliation: | 1. College of Traffic Engineering and Key Laboratory of Road & Traffic Engineering of the Ministry of Education, Tongji University, 4800 Cao''an Road, Shanghai 201804, China;2. Department of Civil & Environmental Engineering, Colorado State University, Fort Collins, CO 80523, United States;1. Division of Forest, Nature and Landscape, Department of Earth and Environmental Sciences, KU Leuven, Celestijnenlaan 200E, Box 2411, 3001 Leuven, Belgium;2. CIBIO/Inbio, Centro de Investigação em Biodiversidade e Recursos Genéticos, Universidade do Porto, Campus Agrário de Vairão, R. Padre Armando Quintas, n° 7, 4485-661 Vairão, Portugal;3. Department of Forest Management and Geodesy, Faculty of Forestry, Technical University in Zvolen, 960-53 Zvolen, Slovakia;4. Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, Kreutzwaldi 5, Tartu 51014, Estonia;5. Centre National de la Propriété Forestière, 47 rue de Chaillot, 75116 Paris, France;6. Forest and Nature Conservation Policy Group, Wageningen University & Research, P.O. Box 47, 6700 AA Wageningen, The Netherlands;7. University Stefan cel Mare Suceava, Romania, Universitatii str. 13, Suceava 720229, Romania;8. Earth and Life Institute, Environmental Sciences, Université catholique de Louvain, Croix du Sud 2, Box L7.05.09, 1348 Louvain-la-Neuve, Belgium;9. Forest & Nature Lab, Ghent University, Geraardsbergsesteenweg 267, Gontrode, 9090 Melle, Belgium;10. European Forest Institute (EFIMED), Sant Pau Historical Site, Sant Leopold Pavilion, carrer Sant Antoni Maria Claret 167, 08025 Barcelona, Spain |
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| Abstract: | We consider a variant of the view maintenance problem: How does one keep a materialized view up-to-date when the view definition itself changes? Can one do better than recomputing the view from the base relations? Traditional view maintenance tries to maintain the materialized view in response to modifications to the base relations; we try to “adapt” the view in response to changes in the view definition.Such techniques are needed for applications where the user can change queries dynamically and wants to see the changes in the results fast. Data archaeology, data visualization, and dynamic queries are examples of such applications. Views defined over the Internet tend to evolve and our technique can be useful for adapting such views.We consider all possible redefinitions of SQL SELECT-FROM-WHERE-GROUP-BY-HAVING, UNION, and EXCEPT views, and show how these views can be adapted using the old materialization for the cases where it is possible to do so. We identify extra information that can be kept with a materialization to facilitate redefinition. Multiple simultaneous changes to a view can be handled without necessarily materializing intermediate results. We identify guidelines for users and database administrators that can be used to facilitate efficient view adaptation.We perform a systematic experimental evaluation of our proposed techniques. Our evaluation indicates that adaptation is much more efficient than rematerialization in most cases. In-place adaptation methods are better than the non-in-place methods when the change is small. We also point out some important factors that can impact the efficiency of adaptation. |
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