Exploiting maximal redundancy to optimize SQL queries

  • Authors:

  • Bin Cao;Antonio Badia

  • Affiliations:

  • Indiana University, Computer Science Department, 47405, Bloomington, IN, USA;University of Louisville, Computer Engineering and Computer Science Department, 40292, Louisville, KY, USA

  • Venue:
  • Knowledge and Information Systems
  • Year:
  • 2009

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Abstract

Detecting and dealing with redundancy is an ubiquitous problem in query optimization, which manifests itself in many areas of research such as materialized views, multi-query optimization, and query-containment algorithms. In this paper, we focus on the issue of intra-query redundancy, redundancy present within a query. We present a method to detect the maximal redundancy present between a main (outer) query block and a subquery block. We then use the method for query optimization, introducing query plans and a new operator that take full advantage of the redundancy discovered. Our approach can deal with redundancy in a wider spectrum of queries than existing techniques. We show experimental evidence that our approach works under certain conditions, and compares favorably to existing optimization techniques when applicable.