Toward Practical Query Evaluation for Constraint Databases

  • Authors:

  • Alexander Brodsky;Joxan Jaffar;Michael J. Maher

  • Affiliations:

  • Dept. of Information and Software Systems Engineering, George Mason University, Fairfax, VA 22030, USA. E-mail: brodsky@isse.gmu.edu;Dept. of Information Systems and Computer Science, National University of Singapore, Lower Kent Ridge Road, Singapore 119260. E-mail: joxan@iscs.nus.sg;School of Computing and Information Technology, Griffith University, Nathan, 4111, Australia. E-mail: mjm@cit.gu.edu.au

  • Venue:
  • Constraints
  • Year:
  • 1998

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Abstract

Linear constraint databases (LCDBs) extend relational databases toinclude linear arithmetic constraints in both relations and queries. A LCDBcan also be viewed as a powerful extension of linear programming (LP) wherethe system of constraints is generalized to a database containingconstraints and the objective function is generalized to a relational querycontaining constraints. Our major concern is query optimization in LCDBs.Traditional database approaches are not adequate for combination with LPtechnology. Instead, we propose a new query optimization approach, based onstatistical estimations and iterated trials of potentially betterevaluation plans. The resulting algorithms are not only effective on LCDBs,but also applicable to existing query languages. A number of specificconstraint algebra algorithms are also developed: select-project-join fortwo relations, constraint sort-join and constraint multi-join.