| 摘要 |
PROBLEM TO BE SOLVED: To provide a query optimizer for attaining the query optimization of a database system. SOLUTION: A system for facilitating query optimization in a data repository comprises a query component for receiving a query, inclusive of an original predicate, to be processed aimed at data of the data repository, and a predicate component for processing and transforming the original predicate into one or a plurality of new predicates inclusive of an implied predicate, wherein the implied predicate is processed aimed at the data to return a best solution such that a total evaluation cost is significantly reduced. Thereby, a query optimization component is allowed to introduce additional predicates into the query for facilitating the following: additional predicates render the same results as those of the original query, and are used as dictated by rules passed to the optimization component or rules for specifying whether the new predicate is equivalence (to substitute the old predicate) or implication (wherein the old predicate is preserved); the additional predicates are considered as cost-based alternatives, and discarded if not useful, and the predicates can be tied to index utilization and can take into consideration both standard and multi-valued indices. COPYRIGHT: (C)2005,JPO&NCIPI
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