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Research Of Query Optimization Based On Join Index

Posted on:2007-05-19Degree:MasterType:Thesis
Country:ChinaCandidate:Z P NiFull Text:PDF
GTID:2178360242961909Subject:Computer software and theory
Abstract/Summary:PDF Full Text Request
In the database system, the speed of query processing affect the life of application system, all kinds of DBMS attach great importance of query optimization. Join, as relational database model's basic operation, is used much, which operates on different relations and the cost of execution is large. So the key of query optimization is optimization of multi-join query. This paper will optimize the processing of join query based on join index.The discussion on the optimization of multi-join query is usually about the order of join, which first executes the join cost minimum. This paper will neglect this section and focus on the optimization of join operation, namely the improvement of join algorithm. The algorithm based on join index takes use of the prejoin information in the index to optimize the query. The join index will cost much for maintenance, because it is generated by the prejoin and built on multiple relations. For consideration of affection to the whole DBMS, in the condition of complex query, the algorithm has been optimized based on the analysis and camparion of the traditional join index algorithm. For the reason of the no order of space data, the algorithm based on join index have to improve for it. The key problem of optimal page-access sequence with a fixed Buffer has been analyzed.On the basis of traditional join algorithm, this paper implements an optimized algorithm. The improved algorithm should perform better, because it uses best of allocated memory, only scans the parts of relation which will produce the join result, and avoid most redundant I/O. All kinds of element, which would affect the performance of algorithm, have been considered in the experiment. And the experimental data in different conditions has been used to test the performance of algorithms in the system for the validation of the point above.
Keywords/Search Tags:DBMS, query optimization, join query, spatial join, join index
PDF Full Text Request
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