On the Optimization of Query Plans in Multistores (Discussion Paper)

Multistores are data management systems that facilitate query processing across databases based on different data models; in addition to distributing data, integration and data fusion activities are necessary to address complexities such as schema heterogeneity and data replication. Our multistore solution relies on a dataspace to provide the user with an integrated view of the available data and enables the formulation and execution of GPSJ queries. In this paper, we outline a technique to optimize the execution of GPSJ queries by formulating and evaluating different execution plans on the multistore. In particular, we identify different strategies to carry out joins and data fusion by relying on different schema representations; then, a self-learning black-box cost model is used to estimate execution times and select the most efficient plan. The experiments assess the effectiveness of the cost model in choosing the best execution plan.