一种改进的查询优化技术———分裂大表

<title>An improvement technology of query optimization-split large table

为了提高数据库应用系统的响应速度,提出了一种改进的分裂大表的方法,即在永久分裂的基础上加设一个索引表,索引表中存放各子表的名称和该子表分裂的条件,索引表是该类信息的惟一操作入口.采用分裂大表方法后,数据的查询、增加、修改和删除都变得非常简单.通过计算得出:如果数据库等长分裂为n个子表,若查询无分组统计,查询速度接近于未分裂之前的1/n;若查询是分组统计,则接近于未分裂之前的1/n2;其他情况下,也显著提高了查询速度,且对数据库空间的影响甚微.

<Abstrcat>To improve the speed of the response in the database application system,a betterment and split large table is proposed.The split large table means adding an index table on the split permanence.In the index table, there are names of every subtable and their conditions.By this way,everything becomes simpler than before,like query,addition,modify,delete,and so on.This can be shown through calculation:First,the database split n subtables which have equal length;if the query has no statistics by group,the speed of the query approximately is 1/n of the speed before the split.Second,if the query with statistics by group,then the speed nearly 1/n2 than before.Last in other conditions,the speed can be obviously improved and there is little effect on the space of database.