| 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 |
| 关键词: 关系数据库,多元连接查询,查询优化,并行执行,执行依赖. |
| DOI： |
| 分类号: |
| 基金项目:本文研究得到国防预研基金资助. |
|
| An Improved Optimizing Method for Multi-join Queries |
|
ZHONG Wu,HU Shou-ren
|
| Abstract: |
| M. S. Chen has put forward heuristics GMC and GMR, 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(n2), 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 GMC and GMR, which benefits from the following: the operation order of two arbitrary adjacent internal nodes (join operations) is optimum. |
| Key words: Relational database, multi-join queries, query optimization, parallel execution, executinon dependency. |
