Research On Query Optimization Algorithm Of Distributed Data Base

This paper introduces the basic concept of distributed database system,such as the mode architecture and system architecture of DDBS,the principle and classification of data fragmentation,the strategy of data distribution.This paper describes the management processing of distributed query.This paper give emphasis to the research on the regular optimization algorithms of distributed query,such as the optimization algorithm based on the regulation of relation algebra equivalence transformation,the optimization algorithm based on join,the optimization algorithm based on semi join,SDD₁ algorithm,the greedy algorithm based on query graph. On the basis of the research on the SDD₁ algorithm and the greedy algorithm based on query graph,this paper design a new algorithm named the query optimization algorithm based on multiple relations semi join,which integrate the characteristics of SDD₁ algorithm and the greedy algorithm based on query graph,this new algorithm can be applied to the circumstance in which the cache of DDBS is the final assembly site of temporary query result.The algorithm reduce the temporary result data numer distinctly and reduce the network communication total cost efficiently through experiment.