Volume 39, Number 4, August 2021
|Page(s)||909 - 918|
|Published online||23 September 2021|
Optimization of correlate subquery based on distributed database
School of Computer Science, Northwestern Polytechnical University, Xi’an 710072, China
2 Bank of Communications, Shanghai 200120, China
Subquery is widely used in database. It can be divided into related subquery and non-related subquery according to whether it is dependent on the table of the parent query. For related subqueries, it is necessary to take a tuple from the parent query before executing the subquery, that is, the content of the subquery needs to be repeatedly operated. Disk access costs of this strategy is very big, in the distributed database, because of data communication overhead, in the parent query yuan set is too low efficiency, therefore, for the class sub queries, on the basis of the optimization of the existing query strategy, combining with the characteristics of distributed database, put forward by the subquery on to join queries, eliminate redundant clauses in the subquery, eliminate accumulation function method based on distributed database query optimization strategy, and the effectiveness of the present optimization strategy is verified by experiment.
Key words: Distributed database / Correlate subquery optimization / rule-based optimization
关键字 : 分布式数据库 / 相关子查询优化 / 基于规则的优化
© 2021 Journal of Northwestern Polytechnical University. All rights reserved.
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