摘要
现代关系数据库查询优化器通常根据查询代价评估不同查询计划的执行效率,对查询计划中产生的中间结果集的错误预测是造成优化器效率低下的主要原因。为了解决这个问题,本文介绍一种新的SPS(Statistics Predict Set)查询优化方法,该方法能够有效地解决这方面的问题。
Modem optimizers generally explore many altemative query plans in a cost-based manner. The eo6t estimation for a plan depends on several factors, among these factors, the intermediate-result size estimation is the main source of low efficiency during optimization. To address this limitation, this thesis introduces the concept of SPS, which are statistics built on query expressions. SP directly and accurately models intermediate results in a query execution plan, and therefore avoid error-prone simplifying assumptions during cardinality estimation.
出处
《计算机与现代化》
2006年第7期33-35,共3页
Computer and Modernization
关键词
关系数据库
查询处理
relational datahase
query proessing
