中间件异构数据库集成中基于半连接的查询优化算法

Query Optimization Algorithm for Mediator Heterogeneous Database Integration Based on Semi-join

全局查询效率一直是中间件异构数据库集成中的热点和难点问题,由于目前异构数据库绝大多数是关系型数据库,所以采用半连接方法优化连接操作,并在半连接图的基础上提出了多个站点的半连接执行方案优化算法,该算法根据半连接图生成有向无序树,使多个半连接操作能够并行执行,经分析能有效地提高全局查询效率.

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.