Query optimization system, query optimization devices, and query optimization method

摘要

Under the reasonable judgment, considering it should be placed on any distributed storage site, can be realized in the implementation stage query optimization intermediate results of a query that occurs as a result of optimization. First, I retrieve the numerical information on the reliability and latency on the site that holds the data. Next, information about the latency, and it is superimposed on the cost value of the reciprocal of the query numerical information on the reliability, to determine the extended cost value. Next, the cost value is to select a replica of a reasonable upper level specified value. Next followed a read-ahead by creating a copy of the processing system itself adds 1 to the maximum block size is a parameter of the algorithm on in order to select where to place the site of intermediate outcomes generated as a result of the optimization. Next, the result of the look-ahead, to be placed on the site of one or more intermediate outcomes. This, I will evaluate the placement method of intermediate results of the query.