Analysis of two existing and one new dynamic programming algorithm for the generation of optimal bushy join trees without cross products

  • Authors:
  • Guido Moerkotte;Thomas Neumann

  • Affiliations:
  • University of Mannheim, Mannheim, Germany;Max Planck Institute for Informatics, Saarbrücken, Germany

  • Venue:
  • VLDB '06 Proceedings of the 32nd international conference on Very large data bases
  • Year:
  • 2006

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Abstract

Two approaches to derive dynamic programming algorithms for constructing join trees are described in the literature. We show analytically and experimentally that these two variants exhibit vastly diverging runtime behaviors for different query graphs. More specifically, each variant is superior to the other for one kind of query graph (chain or clique), but fails for the other. Moreover, neither of them handles star queries well. This motivates us to derive an algorithm that is superior to the two existing algorithms because it adapts to the search space implied by the query graph.