Journal of Systems Engineering and Electronics ›› 2011, Vol. 33 ›› Issue (4): 938-942.doi: 10.3969/j.issn.1001-506X.2011.04.44

• 软件、算法与仿真 • 上一篇    下一篇

实化外连接视图的增量计算

邹先霞1,3, 贾维嘉1,2, 潘久辉3   

  1. 1. 中南大学信息科学与工程学院, 湖南 长沙 410083; 
    2. 香港城市大学计算机系, 香港 九龙;
    3. 暨南大学计算机系, 广东 广州 510632
  • 出版日期:2011-04-25 发布日期:2010-01-03

Incremental computation of materialized outer join views

ZOU Xian-xia1,3, JIA Wei-jia1,2, PAN Jiu-hui3   

  1. 1. Department of Computer Science, Central South University, Changsha 410083, China;
    2. Department of Computer Science, City University of Hong Kong, Kowloon, China;
    3. Department of Computer Science, Jinan University, Guangzhou 510632, China
  • Online:2011-04-25 Published:2010-01-03

摘要:

针对实化外连接视图的增量维护问题,提出了利用独立计算表达式计算辅助增量的算法。该方法利用外连接运算的连接析取范式,为各个析取项建立独立计算表达式,然后利用多个独立表达式之间的公共子表达式来计算实化外连接视图的辅助增量。该方法对实化外连接SPOJ(select project outer join) 视图定义没有其他的限制条件,试验结果表明,与相同条件的算法比较起来,该算法有效地降低了计算代价。

Abstract:

The algorithm for maintaining materialized outerjoin views is proposed to compute the secondary delta by the independent computation of terms. In this algorithm, select project outer join (SPOJ) views are rewritten as the join disjunctive normal form first. Then the independent computation of terms is derived from every normal term. Finally common sub expressions extracted from all of the computation terms are utilized to compute the secondary delta of materialized outer join views. Experimental results show that the algorithm can reduce the computational cost effectively compared with other counterparts under the same conditions, and furthermore it poses no restrictions on SPOJ views.