Optimal top-down join enumeration

Abstract

Most contemporary database systems perform cost-based join enumeration using some variant of System-R's bottom-up dynamic programming method. The notable exceptions are systems based on the top-down transformational search of Volcano/Cascades. As recent work has demonstrated, bottom-up dynamic programming can attain optimality with respect to the shape of the join graph; no comparable results have been published for transformational search. However, transformational systems leverage benefits of top-down search not available to bottom-up methods.