Industrial-strength parallel query optimization: Issues and lessons

摘要

In the industrial context of the EDS project, we have designed and implemented a query optimizer which we have integrated within a parallel database system. The optimizer takes as input a query expressed in ESQL, an extension of SQL with objects and rules, and produces a minimum cost parallel execution plan. Our research agenda has focused on several difficult problems: support of ESQL's advanced features such as path expressions and recursion, modelling of parallel execution spaces and extensibility of the search strategy. In this paper, we give a retrospective on the optimizer project with emphasis on our design goals, research contributions and implementation decisions. We also describe the current optimizer prototype and report on experiments performed with a pilot application. Finally, we present the lessons learned.