Adaptive Optimisation For Continuous Multi-Way Joins Over RDF Streams

Abstract

The join operator is a core component of an RDF Stream Processing engine. The join operations usually dominate the processing load of a query execution plan. Due to the constantly updating nature of continuous queries, the query optimiser has to frequently change the optimal execution plan for a query. However, optimising the join executing plan for every execution step might be prohibitively expensive, hence, dynamic optimisation of continuous join operations is still a challenging problem so far. Therefore, this paper proposes the first adaptive optimisation approach towards this problem in the context of RDF Stream Processing. The approach comes with two dynamic cost-based optimisation algorithms which use a light-weight process to search for the best execution plan for every execution step. The experiments show the encouraging results towards this direction.