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Query optimization processing unit in the integrated heterogeneous database systems, query optimization processing method, recording medium recording a program and a program to execute that method on a computer
Query optimization processing unit in the integrated heterogeneous database systems, query optimization processing method, recording medium recording a program and a program to execute that method on a computer
PROBLEM TO BE SOLVED: To reduce the number of exchanges with a wrapper module, to reuse an optimum access plan, and to prevent reuse of a non-optimum access plan.;SOLUTION: An access plan generation means 112 inquires whether an access plan capable of processing an inquiry request is present in an access plan holding means 113 or not. In the absence, the generation means 112 enumerates tree structures expressing combinations of relational algebra of operators showing the inquiry request to generate the access plan. When operation causing a change of contents of table data managed by a database server 102a, 102b is executed to the database server 102a, 102b, an access plan discard means 122a, 122b indicates the access plan holding means 113 to discard the access plan using data of the database server 102a, 102b.;COPYRIGHT: (C)2004,JPO
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