Operadores de junção baseados em mecanismos de hash para o processamento de consultas em bancos de dados.

Join algorithms constitute a key element for processing queries on databases. In this paper, the evolution of hash-based join algorithms is investigated. Conventional algorithms such as Simple Hash Join, Grace Hash Join and Hybrid Hash Join which were designed for conventional databases architectures are described and analyzed. Furthermore, algorithms such as Symmetric Hash Join, MobiJoin, Hash-Merge Join and MJoin for implementing the join operator in environments with more complex query processing requirements (e.g. mobile computing environment) are presented and analyzed as well.Os algoritmos de junção constituem um elemento chave para o desempenho do processamento de consultas. Com a evolução dos ambientes de execução de consultas tornou-se necessária o desenvolvimento de algoritmos mais eficientes para implementar o operador de junção. Neste trabalho é realizado um estudo sobre a evolução dos algoritmos de junção baseados na técnica de hashing. Serão analisadas estratégias convencionais como o Simple Hash Join, o Grace Hash Join e o Hybrid Hash Join, projetadas para arquiteturas de bancos de dados convencionais, até aquelas capazes de oferecer suporte a ambientes com processamentos de consultas mais complexos, como os de computação móvel. Os algoritmos hash capazes de atender a algumas das necessidades destes novos ambientes incluem o Symmetric Hash Join, o MobiJoin, o Hash-Merge Join e o MJoin

Quality of Service and Optimization in Data Integration Systems

This work presents techniques for the construction of a global data integrations system. Similar to distributed databases this system allows declarative queries in order to express user-specific information needs. Scalability towards global data integration systems and openness were major design goals for the architecture and techniques developed in this work. It is shown how service composition, extensibility and quality of service can be supported in an open system of providers for data, functionality for query processing operations, and computing power.Diese Arbeit präsentiert Techniken für den Aufbau eines globalen Datenintegrationssystems. Analog zu verteilten Datenbanken unterstützt dieses System deklarative Anfragen, mit denen Benutzer die gesuchte Information beschreiben können. Die Skalierbarkeit in einem globalen Kontext und die Offenheit waren hauptsächliche Entwicklungsziele der Architektur und der Techniken, die in dieser Arbeit entstanden sind. Es wird gezeigt wie Dienstekomposition, Erweiterbarkeit und Dienstgüte in einem offenen System von Anbietern für Daten, Anfrageverarbeitungsfunktionalität und Rechenleistung unterstützt werden können

Accurate Modeling of The Hybrid Hash Join Algorithm

: The join of two relations is an important operation in database systems. It occurs frequently in relational queries, and join performance is a significant factor in overall system performance. Cost models for join algorithms are used by query optimizers to choose efficient query execution strategies. This paper presents an efficient analytical model of an important join method, the hybrid hash join algorithm, that captures several key features of the algorithm's performance -- including its intra--operator parallelism, interference between disk reads and writes, caching of disk pages, and placement of data on disk(s). Validation of the model against a detailed simulation of a database system shows that the response time estimates produced by the model are quite accurate. 1 Introduction Relational database systems organize information into a collection of tables. The relational join operator is used to relate information from two or more tables. Thus, joins are a frequently occurrin..