Research on Distance Join Selectivity(JS) Estimation for Spatial Database 空间数据库中距离连接选择率估计方法研究
Distance join is widely used in spatial database. Selectivity estimation for distance join is the basis of optimizing the query of the distance. 距离连接在空间数据库中有着广泛的应用,而距离连接的选择度估计是优化距离查询的基础。
Each join reduces the size of the fact table by one-tenth due to selectivity of the table filter on each dimension table. 由于每个维度表过滤的选择度,每次连接都会减少事实表大小的十分之一。
The other is based on virtual join, which reduce the cost of both communication and local processing, and it is adaptive to different values of selectivity. 另一种是基于虚拟联接的优化算法,它兼顾了网络费用和局部处理费用,并对选择度有自适应性。