An important problem in the physical design of databases is the selection of secondary indices. In general, this problem can not be solved in an optimal way due to the complexity of the selection process. Often use is made of heuristics such as the well-known ADD and DROP algorithms. In this paper it will be shown that frequently used cost functions can be classified as super- or submodular functions. For these functions several mathematical properties have been derived which reduce the complexity of the index selection problem. These properties will be used to develop a tool for physical database design and also give a mathematical foundation for the success of the before-mentioned ADD and DROP algorithms. Keywords: Physical database design, Secondary index selection, ADD and DROP algorithms, Supermodular functions, Submodular functions. 1 Introduction Physical database design is an important step in designing databases and aims to generate efficient storage structures for the data....

In some key database applications, such as data mining, a sequence of interdependent queries may be posed simultaneously to the DBMS. The optimization of such sequences is called multi-query optimization, and it attempts to exploit these dependencies in the derivation of a query evaluation plan (qep). Although it has been observed and demonstrated by several researchers that exploitation of dependencies speed up the query processing, limited research has been reported how to benefit from multi-query optimization, taking the capabilities of existing query optimizers into account. This is exactly the topic of this paper. Since existing optimizers are able to optimize queries in which a restricted number of basic operations appears, e.g., number of joins is limited to 10, and the optimization of a query is relatively expensive, we attempt to profit from multi query optimization under the condition that queries are passed only once and separately to the optimizer. We propose a two...

Physical database design can be marked as a crucial step in the overall design process of databases. The outcome of physical database design is a physical schema which describes the storage and access structures of the stored database.

Several indexing techniques have been proposed to accelerate database operations in object-oriented databases. A database operation gives rise to the processing of a path. We address the problem of optimal index configuration for a given logical schema, the workload defined on the schema and some other database characteristics such as the cardinality of a class, page size, etc. As will be shown an optimal index configuration for the workload can be achieved by splitting the paths into subpaths and by indexing each subpath optimal. For the moment we take a limited number of existing indexing techniques into account (simple index, inherited index, nested inherited-index, multi-index, and multi-inherited index) and the possibility of not indexing a (sub)path. However, the principles of the algorithm will remain the same adding more indexing techniques. 1 Introduction Object-oriented data models are based on some fundamentals concepts which will be discussed briefly. A real world entity i...

In some key database applications, a sequence of interdependent queries may be posed simultaneously to the DBMS. The optimization of such sequences is called multi-query optimization, and it attempts to exploit these dependencies in the derivation of a query evaluation plan (qep). Although it has been observed and demonstrated by several researchers that exploitation of dependencies speed up the query processing, limited research has been reported how to benefit from multi-query optimization, taking the capabilities of existing query optimizers into account. This is exactly the topic of this paper. Since existing optimizers are able to optimize queries in which a restricted number of basic operations appears, e.g., number of joins is limited to ten, and the optimization of a query is relatively expensive, we attempt to profit from multi query optimization under the condition that queries are passed only once and separately to the optimizer. We propose a two-step optimization procedure....

In a high-level query language such as SQL, queries yield the same result no matter how the logical schema is physically implemented. Nevertheless, a query's cost can vary by orders of magnitude among different physical implementations of the same logical schema, even with the most modern query optimizers. Therefore, designing a low-cost physical implementation is an important pragmatic problem. Physical database design involves deciding on primary and secondary indexes, deciding how to vertically partition logical tables, deciding which queries should be materialized views, etc. These decisions require a sophisticated understanding of physical design options and query strategies, and involve estimating query costs, a tedious and error-prone process when done manually. We have devised a simple framework for automating physical design in relational or post-relational DBMSs and in database programming languages. Within this framework, design options are uniformly represented as "features", and designs are represented by "conflict"-free sets of features. Mutually exclusive features (e.g. two primary indexes on the same table) con ict. Using features simplifies the incorporation of a wide variety of design options and supports extensibility � adding a new design option (e.g. a new index

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Research and development in database technology evolves in several directions, which are not necessarily divergent. A number of these directions might be promising for military information systems as well. In this paper, we discuss the potentials of multi-media databases and data mining. Both directions focuss on the handling of a vague information need of a user. In general, data mining systems allow a higher degree of vagueness than multi-media systems. Information systems that are able to handle vague information needs adequately will improve the decision making process of militaries. 1