Wen-Chi Hou
Abstract
We consider those database environments in which queries have strict timing constraints, and develop a time-constrained query evaluation methodology. For aggregate relational algebra queries, we describe a time constrained query evaluation algorithm. The algorithm, which is implemented in our prototype DBMS, iteratively samples from input relations, and evaluates the associated estimators developed in our previous work, until a stopping criterion (e.g., a time quota or a desired error range) is satisfied.
To determine sample sizes at each stage of the iteration (so that the time quota will not be overspent) we need to have (a) accurate sample selectivity estimations of the RA operators in the query, (b) precise time cost formulas, and (c) good time-control strategies. To estimate the sample selectivities of RA operators, we use a runtime sample selectivity estimation and improvement approach which is flexible. For query time estimations, we use time-cost formulas which are adaptive and precise. To use the time quota efficiently, we propose statistical and heuristic time-control strategies to control the risk of overspending the time quota. Preliminary evaluation of the implemented prototype is also presented.
- AbGM 88 Abbott, R., and Garcia-Molina, H., "Scheduling Realtime Transactions", Proc., VLDB 1988 (Also in ACM SIGMOD RECORD, 1988). Google Scholar
Digital Library
- Coch 77 Cochran, W.G., "Sampling Techniques", Third Ed. John Wiley & Sons, 1977.Google Scholar
- Chri 83 Christodoulakis, S., "Estimating Record Selectivities", Information Systems, Vol 8, 1983.Google Scholar
- DFHO 86 Datta, A., Foumier, B., Hou, W-C., and Ozsoyoglu, G., "The Implementation of SSDB", Proc. 3rd SSDB workshop, I~xernbourg, July 1986. Google ScholarDigital Library
- Good 49 Goodman, L A., "On the Estimation of the Number of Classes in a Population", Ann. Math. Star., Vol. 20, 1949.Google ScholarCross Ref
- HoOT 88 Hou, W-C., Ozsoyoglu, G., Taneja, B., "Statistical Estimators for Relational Algebra Expressions", ACM PODS Confer~mce, March 1988. Google ScholarDigital Library
- HoOT 88a Hou, W-C., Ozsoyoglu, G., Taneja, B., "Processing Aggregate Relational Queries with Hard Time Constraints", CWRU Tech. Rep. CES-88-26, Dec. 1988.Google Scholar
- HouO 88 Hou, W-C. Ozsoyoglu, G., "StatisLical Estimators for Aggregate Relational Algebra Expressions", May 1988.Google Scholar
- JoWi 82 Johnson, R., and Wichem, D., "Applied Multivariate Statistical Analysis", Prentice Hall 1982. Google ScholarDigital Library
- Liu 68 Liu, C.L, "Introduction to Cornbinatodal Mathematics", McGraw-Hill, 1968.Google Scholar
- MuDe 88 MuralJkrishna, M. and Dewitt, D., "Equidepth histograms for estimating selectivity factors for multidimensional queries", ACM SIGMOD 1988.Google Scholar
- PSCo 84 Piatetsky-Shapiro, G. and CormeIl, G., "Accurate Estimation of the number of tuples satisfying a condition", ACM SIGMOD conference, 1984. Google ScholarDigital Library
- OzHO 88 Ozsoyoglu, G., Hou, W-C., Ola, A., "On Database Systems for Programming Logic Controllers", 1988.Google Scholar
- Rowe 85 Rowe, N. C., "Antisampling for Estimation : An overview", IEEE TSE Oct. 1985. Google ScholarDigital Library
- SACL 79 Sellinger,P., Astrahan, M., Chambedein, D., Lorie,R., Price, T., "Access path selection in a relational database management system", ACM SIGMOD 1979. Google ScholarDigital Library
Index Terms
- Processing aggregate relational queries with hard time constraints
Recommendations
Processing aggregate relational queries with hard time constraints
SIGMOD '89: Proceedings of the 1989 ACM SIGMOD international conference on Management of dataWe consider those database environments in which queries have strict timing constraints, and develop a time-constrained query evaluation methodology. For aggregate relational algebra queries, we describe a time constrained query evaluation algorithm. ...
Processing Aggregate Queries with Materialized Views in Data Warehouse Environment
Materialized views, which are derived from base relations and stored in the database, offer opportunities for significant performance gain in query evaluation by providing quick access to the pre-computed data. A materialized view can be utilized in ...
Comments