Scrambling query plans to cope with unexpected delays
Scrambling query plans to cope with unexpected delays
Dynamic query operator scheduling for wide-area remote access
Dynamic query operator scheduling for wide-area remote access
An adaptive query execution system for data integration
SIGMOD '99 Proceedings of the 1999 ACM SIGMOD international conference on Management of data
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In data integration systems, a central site often maintain a global catalog of all available data sources, and maintain statistics to allow the query optimizer to generate a good query plan. These statistics could be updated in a lazy manner during query execution time. A user query is often broken into several query fragments, and a centralized task scheduler schedules the execution of the respective query fragment, fetching data from the various data sources. This is then integrated at the central site and presented to the user. As data sources are introduced, there is a need to update the global catalog from time to time. However, due to the autonomous nature of the data sources, which are maintained by local administrators, it is difficult to ensure accurate statistics as well as the availability of the data sources. In addition, since the data are integrated at the central site, the central site could become a potential bottleneck. The unpredictable nature of the wide area environment further exacerbate the problem of query processing.In this paper, we present our ongoing work on dbRouter, a distributed query optimization and processing framework for open environment. The dbRouter provides mechanisms to faciliate the discovery of new data sources, performs distributed query optimization, and manages the routing of data to its destination for processing.