Many applications require that large amounts of data are deleted from the database -- typically, such bulk deletes are carried out periodically and involve old or out-of-date data. If the data is not partitioned in such a way that bulk deletes can be carried out by simply deleting whole partitions, then most current database products execute such bulk delete operations very poorly. The reason is that every record is deleted from each index individually. This paper proposes and evaluates a new class of techniques to support bulk delete operations more efficiently. These techniques outperform the "record-at-a-time" approach implemented in many database products by about one order of magnitude. 1. Introduction Sometimes we are confronted with more data than we can really use, and it might be wisest to forget and to destroy most of it. (Donald Knuth, The Art of Computer Programming) For many companies, the cost to administrate their databases has increased dramatically in the last coupl...

Topological predicates like overlap, inside, meet, and disjoint uniquely characterize the relative position between objects in space. They have been the subject of extensive interdisciplinary research. Spatial database systems and geographical information systems have shown a special interest in them since they enable the support of suitable query languages for spatial data retrieval and analysis. A look into the literature reveals that the research efforts so far have mainly dealt with the conceptual design of and the reasoning with these predicates while the development of efficient and robust implementation methods for them has been largely neglected. Especially the recent design of topological predicates for different combinations of complex spatial data types has resulted in a large increase of their numbers and stressed the importance of their efficient implementation. The goal of this article is to develop efficient implementation techniques of topological predicates for all combinations of the complex spatial data types point2D, line2D, and region2D within the framework of the spatial algebra SPAL2D. Our solution consists of two phases. In the exploration phase described in previous work of the authors, for a given scene of two spatial objects, all topological events are registered in so-called topological feature vectors. These vectors serve as input for the evaluation phase which is the focus of this article and which analyzes the

Optimizing nested queries is an intricate problem. It becomes even harder if in a nested query the linking predicate or the correlation predicate occurs disjunctively. We present the first unnesting strategy that can effectively deal with such queries. The starting point of our approach is to translate SQL into the relational algebra extended by bypass operators. Then we present for the first time unnesting equivalences which are valid for algebraic expressions containing bypass operators. Applying these to the translated queries results in our effective unnesting strategy for nested SQL queries with disjunction. With an extensive experimental study (including three commercial DBMSs), we demonstrate the possible performance gains of our approach. 1

Topological relationships between spatial objects such as overlap, disjoint, and inside have for a long time been a focus of research in a number of disciplines like cognitive science, robotics, linguistics, artificial intelligence, and spatial reasoning. In particular as predicates, they support the design of suitable query languages for spatial data retrieval and analysis in spatial database systems and Geographic Information Systems. While conceptual aspects of topological predicates (like their definition and reasoning with them) as well as strategies for avoiding unnecessary or repetitive predicate evaluations (like predicate migration and spatial index structures) have been emphasized, the development of correct and efficient implementation techniques for them has been rather neglected. Recently, the design of topological predicates for different combinations of complex spatial data types has led to a large increase of their numbers and accentuated the need for their efficient implementation. The goal of this article is to develop efficient implementation techniques of topological predicates for all combinations of the complex spatial data types point2D, line2D, and region2D,as

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