Research On Data Query Optimization Algorithm Of Distributed Database

This article deeply studies the semi-join algorithm of the DDB query processing and optimization,states the shortage of the semi-join algorithm's ignorant of local process cost, points out quadratic semi-join based key join relation algorithm,this algorithm considers transmission cost and regards local process cost. When related to multi-relation query,the article researches clauses of joi,query graph,query graph generation tree,chain algorithm and Kruskal algorithm.On these basis,suggests improved quadratic semi-join based query graph division algorithm,this algorithm makes plenty use of data distribution, increases the possibility of query parallel processing, divides up query graph, raises the conception of divisible point and indivisible query graph, and the verdict rules of division point and parallel query graph, to a certain degree, recovers the shortage of exclusive used Kruskal algorithm, experimental result indicates the cost of this algorithm is smaller than the one of Kruskal algorithm,when distributed query quotes more relations,query graph divides more parallel query graph, so shorten the response time of query, makes the cost of query smaller.