SURVEY ON IMPACT OF SEMI JOIN IN DISTRIBUTED QUERY PROCESSING

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E. Padmalatha
S. Sailekya

Abstract

Distributed system query processing is an essential factor in the presentation of a distributed data bases. Query processing in rapports of communication cost and processing cost should be minimum in the distributed data bases. As relations are partitioned based on horizontal or vertical partitions, a query is divided in to sub queries on the partitions that require operations at geographically separated databases. Query optimization is a difficult task in a distributed databases environment as data location becomes a foremost consideration. The query optimizer should select an efficient resultant for the given query, If a poor query execution plan is selected it will lead to a poor performance of the database system. Always the cost of execution of the query subjective function of the system resources needed to execute the query. System resources are like CPU time and the number of read, write operations on a relation. Realistic cost estimates of the optimizer need to evaluate the size of sub-queries. This will play a vital role in the selection of the join order of the relations. To approximation the dimensions of sub-queries, the optimizer needs to know the fussiness of the query basesThis paper briefly described join and semi join operation performance in the distributed data bases and analyzed with the practical application.

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