Loop elimination for database updates

  • Authors:

  • Vadim Savenkov;Reinhard Pichler;Christoph Koch

  • Affiliations:

  • Vienna University of Technology, Austria;Vienna University of Technology, Austria;École Polytechnique Fédérale de Lausanne, Switzerland

  • Venue:
  • BNCOD'13 Proceedings of the 29th British National conference on Big Data
  • Year:
  • 2013

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Abstract

The additional expressive power of procedural extensions of query and update languages come at the expense of trading the efficient set-at-a-time processing of database engines for the much less efficient tuple-at-a-time processing of a procedural language. In this work, we consider the problem of rewriting for-loops with update statements into sequences of updates which do not use loops or cursors and which simultaneously carry out the action of several loop iterations in a set-at-a-time manner. We identify idempotence as the crucial condition for allowing such a rewriting. We formulate concrete rewrite rules for single updates in a loop and extend them to sequences of updates in a loop.