An optimization problem on the selection of secondary keys

摘要: The use of index files for accessing records, on the basis secondary key values is a common feature existing information systems. This method, judiciously applied, provides major improvements in response time, easy to implement and costs relatively little. Moreover, concepts indexes are simple, yet powerful flexible because they provide power handle all kinds queries easily with little loss efficiency. It is, however, important carefully select fields be indexed excessive indexing can result performance degradation. paper presents quantitative tradeoff analysis selection.The problem formulated mathematically as an optimization using indicator function which becomes positive when implementation file desirable negative otherwise. variables this derived from factors that influences system. These include query statistics, frequency speed retrieval, m maintenance relevant files. Two examples illustrating principle application given.