Efficient View Maintenance Using Version Numbers
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Date
2000-02-01T00:00:00Z
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Abstract
Maintaining a materialized view in an environment of multiple, distributed, autonomous data sources is a challenging issue. Given that the view site does not control the transactions at the data sources, results of incremental computation is affected by interfering updates and compensation process is required to resolve such problem. The compensation algorithm in our previous work handles the resolving of interfering updates without making any assumption on the first-sent-first-received and non-lost delivery of messages over the communication network.
In this paper, we improve the incremental computation process by cutting down unnecessary maintenance queries and thus their corresponding query results, through using the knowledge of referential integrity constraints and functional dependencies of the base relations. We reduce the number of times of sending sub-queries to a data source with multiple base relations, as well as avoiding the execution of cartesian products, by using the join graph of the view to determine the access path of querying these base relations. We also provide a compensation algorithm that makes the accessing of multiple base relations from the same data source within a single sub-query possible. Overall performance is improved by cutting down the sending of unnecessary view maintenance queries and results, sizes of results are reduced drastically as cartesian products are avoided, as well as the number of times of issuing sub-queries to each data source.