Abstract. In this paper, the performance and characteristics of the execution of various join-trees on a parallel DBMS are studied. The results of this study are a step into the direction of the design of a query optimization strategy that is fit for parallel execution of complex queries.Among others, synchronization issues are identified to limit the performance gain from parallelism. A new hash-join algorithm is introduced that has fewer synchronization constraints than the known hash-join algorithms. Also, the behavior of individual join operations in a join-tree is studied in a simulation experiment. The results show that the introduced Pipelining hash-join algorithm yields a better performance for multi-join queries. The format of the optimal join-tree appears to depend on the size of the operands of the join: A multi-join between small operands performs best with a bushy schedule; larger operands are better off with a linear schedule. The results from the simulation study are confirmed with an analytic model for dataflow query execution.
In this paper, the performance and characteristics of the execution of various join-trees on a parallel DBMS are studied. The results of this study are a step into the direction of the design of a query optimization strategy that is fit for parallel execution of complex queries.Among others, synchronization issues are identified to limit the performance gain from parallelism. A new hash-join algorithm is introduced that has fewer synchronization constraints than the known hash-join algorithms. Also, the behavior of individual join operations in a join-tree is studied in a simulation experiment. The results show that the introduced Pipelining hash-join algorithm yields a better performance for multi-join queries. The format of the optimal join-tree appears to depend on the size of the operands of the join: A multi-join between small operands performs best with a bushy schedule; larger operands are better off with a linear schedule. The results from the simulation study are confirmed with an analytic model for dataflow query execution.
PRISWDB is a full-fledged parallel, main memory relational database management system the design of which is characterized by two main ideas. In the first place, high performance is obtained by the use of parallelism for query processing and main memory storage of the entire database. In the second place, a flexible architecture for experimenting with functionality and performance is obtained via a modular implementation of the system in an object-oriented programming language. This paper describes the design and implementation of P R I S W D B in detail. Also, a performance evaluation of the system shows that the system is comparable to other state-ofthe-art database machines. The prototype implementation of the system is ready, and runs on a 100-node parallel multiprocessor. The achieved flexibility of the system makes it a valuable platform for research in various directions.Index Terms-Parallel, main memory, relational database management system, design and implementation, architecture, query execution, experimentation, integrity constraints.
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