摘要
Ｍ．Ｓ．Ｃｈｅｎ提出了用于产生具有较低计算代价的ｊｏｉｎ丛树的启发式方法ＧＭＣ和ＧＭＲ．本文在分析相关ｊｏｉｎ操作的次序与计算代价的关系后，给出了时间复杂度为Ｏ（ｎ２）的对ＧＭＣ和ＧＭＲ的改进算法．由于在该算法生成的ｊｏｉｎ丛树中，任意两个相邻的内部结点（ｊｏｉｎ操作结点）的操作次序是最优的，因此，它比ＧＭＣ和ＧＭＲ能进一步降低ｊｏｉｎ丛树的计算代价．
M. S. Chen has put forward heuristics G MC and G MR , which are used to produce a join bushy tree with less total cost. On the basis of his work, the paper gives an improved algorithm with complexity of O(n 2) , by means of analysing relationship between the order of join operations and computing costs. The algorithm can reduce more total cost of a join bushy tree than G MC and G MR , which benefits from the following: the operation order of two arbitrary adjacent internal nodes (join operations) is optimum.
出处
《软件学报》
EI
CSCD
北大核心
1998年第2期125-128,共4页
Journal of Software
基金
国防预研基金
关键词
关系数据库
多元连接查询
查询优化
数据库
Relational database, multi join queries, query optimization, parallel execution, executinon dependency. Class number\ TP311.13
