Iteration of database relations for queries of special form

Abstract

In this paper, the material for compiling a plan of performing “join-selection-projection” queries to relational databases is systematized. This is necessary for counting the number of iterations in the query execution algorithms. The presented topic is relevant for a considerable period of time. However, every time there are new requirements for queries, new methods of data presentation, etc. This leads to the necessity of resolving old problems. Many papers were devoted to various aspects of the optimization of queries to relational databases. Thus, it is possible to define two main directions. They are logical optimization of the queries and physical optimization of the queries execution. The basis of logical optimization is heuristics about the order of relational operations. However, more effective solution to the optimization problem is minimization of input-output operation quantity during the query execution. The approach to the development of the query execution plan on the basis of estimators for input-output operations for conventional and specialized methods of data storage is offered in this paper. The expediency of transformations, use of indexes etc. are determined by estimators.