Scheduling multiple queries in symmetric multiprocessors

Abstract

Traditionally, queries submitted to a database management system are optimized one at a time. However, queries posed to a database usually access some common relations, or share some common intermediate results. Exploiting such sharings can effectively improve the performance of the system. In this paper, we describe our approach to scheduling a group of queries for processing in symmetric multiprocessors. The novel feature of our approach is that we exploit sharings of (base) relations and/or common intermediate results for pipelined plans. We propose an optimization framework that exploits such sharings. Two scheduling algorithms are derived from the framework. The first algorithm, SerialShare, generates a serial plan, while the second algorithm, MultiShare, generates a parallel plan. An analytical model is developed to study the performance of the algorithms. Compared to the traditional method of executing one query after another without sharing, our results show that our proposed algorithms can provide significant performance improvement. © Elsevier Science Inc. 1996.