| 摘要 |
A query access plan for executing a database query is dynamically selected from among multiple alternative query access plans based on the availability of computer resources allocated for running the query. Preferably, a first query access plan is generated based on resources then available, and if it is possible to provide additional resources, one or more alternative plans are generated based on the additional resources. If an alternative plan is significantly better than the original plan based on a comparison of query related parameters, the alternative is chosen for executing the query. Additional resources for running the query may be provided from logically partitioned and/or grid environments.
|
