基于半连接查询优化算法的改进

The Improvement of Query Optimization Algorithm Based on Semi-join

本文阐述了半连接优化算法的基本思想和执行过程,并分析了优缺点。为了改进该算法,本文提出了基于语义缓存机制的PERF连接算法的设想,该算法通过在半连接的基础上把半连接所要传送的中间结果替换成与之一一对应的PERF位向量表来进行传输,这很大程度上降低了传输带价;通过对半连接上的投影等操作采用语义缓存机制来处理,充分的利用缓存项的查询结果,使得访问服务器数据的频率降低,极大地缩短了响应时间。本文还简要的分析了该算法的优缺点。

This paper briefly describes the target of the distributed query optimization,elaborates the basic idea and implementation process of the semi-join optimization algorithm,and analyzes the advantages and disadvantages.In order to improve the algorithm,this paper puts forward the idea of PERF join algorithm based on semantic cache mechanism,which on the basis of semi-join will replace the intermediate results that will be transferred with a corresponding PERF bit vector to transmit,which greatly reduce the transmission cost.This method of handling based on the operation of the projection on semi-join using a semantic cache mechanism,makes full use of the cache entry query results reduces the frequency of accessing to the server data,and greatly shortens the response time.This paper also analyzes the advantages and disadvantages of the algorithm briefly.