Distributed query plan generation using multi-objective ant colony optimisation

Abstract

In distributed relational databases, relations are fragmented and replicated at multiple disparate sites. As a result, for a distributed relational query, the number of possible query plans increases exponentially with an increase in the number of sites containing these relations. This leads to a large search space from which effective and efficient query plans are to be computed. This problem has already been addressed as a single objective optimisation problem using ant colony optimisation. In this paper, this problem is addressed as a bi-objective optimisation problem and solved using multi-objective ant colony optimisation MOACO. Accordingly, a MOACO-based distributed query plan generation DQPG algorithm is proposed herein that generates Top-K query plans for a distributed query. Experimental comparisons of the proposed MOACO-based DQPG algorithm with the existing ACO-based DQPG algorithm show that for higher numbers of relations, the former is able to generate, comparatively, cost-effective Top-K query plans.