Query execution scheduling in parallel object-oriented databases

• Published in: Information and software technology Vol. 41; no. 3; pp. 163 - 178
• Main Authors: Taniar, David, Leung, Clement H.C
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 25.02.1999; Elsevier Science Ltd
• Subjects: Access plans; Computer science; Object oriented programming; Object-oriented technology; Parallel object-oriented databases; Parallel processing; Parallel query execution; Queries; Query scheduling; Scheduling; Searches; Studies; Access plans; Scheduling; Parallel object-oriented databases; Parallel query execution
• ISSN: 0950-5849; 1873-6025
• DOI: 10.1016/S0950-5849(98)00111-6

Complex object-oriented queries generally consist of path expressions and explicit join operations. Since explicit join operations have been acknowledged as the most expensive operations, query executions normally start from the path expressions. Each path expression may form a sub-query. There are two existing strategies to sub-queries processing: ‘serial’ and ‘parallel’ execution scheduling strategies. Serial sub-queries execution corresponds to an execution of the sub-queries one-by-one, whereas parallel sub-queries execution corresponds to simultaneous execution of the sub-queries. When a sub-query is being processed, parallelization techniques may be applied. In this paper, we focus on the scheduling issues of the sub-queries, rather than the parallelization of the sub-queries themselves. Rules are formulated to guide the parallel query execution process. Our analysis shows that when there is no load skew, the serial scheduling strategy is preferred, otherwise the parallel scheduling strategy should be used.