关系闭包的计算

The Efficient Implementation of the Transitive Closure cf Relational Operator

本文涉及演绎数据库递归查询的优化问题,提出算若干计算关系闭包的算法。算法的主要思想是及时地从关系中删去不产生新结果的元组,避免元组间多次重复的连接,提高查询效率。

The recent popular argument in deductive database is how tc implement recursive queries efficiently. A recursive qurey may be translated into au extended relational expression, including the closure operation. This paper presents several algorithms to improve the computation of the closure, The main idea is to reduce the cost of each join by deleting those tuples which produce no new result in each iteration from relavant relations.