摘要
在面向对象数据库中,“联系-选择”复合操作的功能类似于嵌套关系数据库中多个嵌套关系的连接,是查询优化时需要重点考虑的问题.本文首先证明满足一定条件限制的“联系-选择”复合操作可在多项式时间内得到最佳查询方案,然后给出了支持双向联系时“联系-选择”复合操作的一些优化算法.模拟实验表明,文中所提出的优化算法性能平稳,效果很好.
Associate-Select' compound operation, which is similar in functionality tojoin operation of multi-nested relations in nested relational databases, is a key issue ofquery optimization in object-oriented database systems. This paper proves that the opti-mum solution for treelike 'Associate-Select' queries with some restrictions can be obtainedwith polynomial complexity, then presents some algorithrns to deal with the situationwhen birelationship exists in complex objects(for example by defining inverse attribute etal. ). A simulation experiment is performed to demonstrate the steadiness and effectivenes s of the algorithms proposed in the paper.
出处
《软件学报》
EI
CSCD
北大核心
1997年第12期907-913,共7页
Journal of Software
关键词
面向对象
数据库
查询优化
复合操作
Object-oriented database, query optimization, 'associate-select' compound operation