Coarse-grained optimization: techniques for rewriting SQL statement sequences

  • Authors:

  • Tobias Kraft;Holger Schwarz;Ralf Rantzau;Bernhard Mitschang

  • Affiliations:

  • University of Stuttgart, Department of Computer Science, Electrical Engineering and Information Technology, Stuttgart, Germany;University of Stuttgart, Department of Computer Science, Electrical Engineering and Information Technology, Stuttgart, Germany;University of Stuttgart, Department of Computer Science, Electrical Engineering and Information Technology, Stuttgart, Germany;University of Stuttgart, Department of Computer Science, Electrical Engineering and Information Technology, Stuttgart, Germany

  • Venue:
  • VLDB '03 Proceedings of the 29th international conference on Very large data bases - Volume 29
  • Year:
  • 2003

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Abstract

Relational OLAP tools and other database applications generate sequences of SQL statements that are sent to the database server as result of a single information request provided by a user. Unfortunately, these sequences cannot be processed efficiently by current database systems because they typically optimize and process each statement in isolation. We propose a practical approach for this optimization problem, called "coarse-grained optimization," complementing the conventional query optimization phase. This new approach exploits the fact that statements of a sequence are correlated since they belong to the same information request. A lightweight heuristic optimizer modifies a given statement sequence using a small set of rewrite rules. Since the optimizer is part of a separate system layer, it is independent of but can be tuned to a specific underlying database system. We discuss implementation details and demonstrate that our approach leads to significant performance improvements.