Parallel transitive closure computation in relational databases

Abstract

The transitive closure operation is an important extension to relational algebra. Because of its high computation cost, it is of great interest to design efficient parallel algorithms for computing the transitive closure in relational database systems. In this paper, we present a new algorithm to compute transitive closures on SIMD meshes based on relational algebra operations. Double-hash distribution is used to avoid rehashing new tuples for the next join phase. There presently exists no extra step for the redistribution of these tuples. Possible redundant computation between different join phases has been prevented without using global operations. As only regular linear communication occurs on the mesh, and the workload is fully distributed, a speedup of O( n × n) has been achieved, where n × n is the size of mesh. Therefore, this algorithm is an optimal parallel version of the transitive closure algorithms based on relational algebra operations on SIMD meshes.