Query optimisation in a non-uniform bandwidth distributed database system

After over twenty years of study, query optimisation in distributed databases is still an open problem, particularly in a dynamic network environment. The study aims to apply probabilistic optimisation techniques to a system with non-uniform bandwidth between servers to investigate the feasibility of applying such techniques at run-time to accommodate changing network conditions. The cost based optimiser developed manipulates both operator order and the physical locations at which these operators are evaluated, and provides a basis for the detailed examination of resource contention issues or the study of new operator types.