J.M. Morrissey

University of Windsor, Windsor, Ontario, Canada

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Publications (4)0 Total impact

  • Source
    J.M. Morrissey, W.K. Osborn, Y. Liang
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    ABSTRACT: The optimization of general queries in a distributed database management system is an important research issue. The problem is to select the best sequence of database operations that will process the query efficiently and minimize costs. Approaches include algorithms which are join-based, semijoin-based, or a combination of both. The algorithm presented which is based on reduction filters, can process general queries consisting of an arbitrary number of relations and join attributes. Each query is represented by a graph and an adjacency list. Each relation is usually only processed once, to minimize data transfers. However, if a filter changes during use then certain relations must be processed again; a queue is used to record this information. The algorithm consists of two phases: during phase one the adjacency list is used to determine the order in which the filters are constructed and used
    Electrical and Computer Engineering, 2000 Canadian Conference on; 02/2000
  • J.M. Morrissey, O. Ogunbadejo
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    ABSTRACT: Tseng and Chen (1992) presented a new relational operator called a hash-semijoin. They proposed a method which will transform a sequence of semijoins, produced by any existing semijoin-based algorithm, into a more cost effective sequence by replacing some of the semijoins by hash-semijoins. The hash-semijoin can be very effective but some of the benefits may be negated by the occurrence of collisions in the reduction filter. Such collisions mean that the hash-semijoin cannot achieve the same amount of reduction as a semijoin can. However, under certain circumstances, the benefits may greatly outweigh the costs and thus collisions are not a serious problem. But their approach has not been experimentally evaluated. In this paper we explore their hypothesis that traditional algorithms, which use semijoins, can always be improved by replacing some or all of the semijoins by hash-semijoins. Four different algorithms are investigated. Each aims to minimize the amount of data transmitted around the network during distributed query processing
    Electrical and Computer Engineering, 1999 IEEE Canadian Conference on; 02/1999
  • Source
    J.M. Morrissey, W.K. Osborn
    [Show abstract] [Hide abstract]
    ABSTRACT: The optimization of general queries in a distributed database management system is an important research topic. The problem is to select the best sequence of database operations that will process the query and minimize costs. Our algorithm, which is based on reduction filters, can process general queries consisting of an arbitrary number of relations and join attributes. Each query is represented by a graph and an adjacency list. Each relation is usually only processed once-to minimize data transfers. However, if a filter changes during use then certain relations must be processed again-a queue is used to record this information. This work has one serious limitation-we used a “perfect“ hash function which means that collisions are not possible. Experiments showed that our algorithm could reduce data transfers very substantially. However, in a database collisions in the reduction filter are a reality and a problem. Such collisions mean that the hash-semijoin cannot achieve the same amount of reduction as a traditional semijoin would. We investigate the effect that collisions have on the performance of our algorithm
    Electrical and Computer Engineering, 1999 IEEE Canadian Conference on; 02/1999
  • Source
    J.M. Morrissey, W.K. Osborn
    [Show abstract] [Hide abstract]
    ABSTRACT: The optimization of general queries in a distributed database management system is an important research topic. The difficulty is to select the database operations which will process the query and minimize costs. Traditional solutions include the use of heuristic strategies based on semijoin or join operations. We present an approach for general queries which uses reduction filters, which are based on Bloom filters, to minimize data transfers and reduce local processing costs. We discuss related work and present our algorithm-illustrating it with a simple example. We end with a brief discussion of current and future work
    Electrical and Computer Engineering, 1998. IEEE Canadian Conference on; 06/1998

Publication Stats

6 Citations

Institutions

  • 1998–2000
    • University of Windsor
      • Department of Computer Science
      Windsor, Ontario, Canada