Query Optimization Algorithm for Mediator Heterogeneous Database Integration Based on Semi-join
YU Jian-qiao · Journal of Southwest China Normal University · 2010
Global query efficiency is the hot and difficult problem on mediator heterogeneous database integration continuously.Since the vast majority of the current heterogeneous database is relational database,the authors optimize join query based on semi-join,and put forword query optimization algorithm for semi-jion execution plan on several databases on the basis of semi-jion graph.This algorithm produces directed and disordered tree based on semi-join graph,so that number of semi-join operations can be executed in parallel.After analysis,the algorithm can improve global query efficiency greately.