| 摘要 |
A system and method for selectively recompiling stored execution plans within a database system. In one technique the execution plans include respective version numbers of database software operable within the database system during compilation of the respective plans. A request is received to execute one of the stored execution plans, and the stored execution plan is retrieved from computer memory. A version number is obtained of database software operable within the database system during retrieval of the stored execution plan. The obtained version number is compared with the version number associated with the retrieved execution plan. On detecting a mismatch between the obtained version number and the retrieved version number, the stored execution plan is recompiled. In another technique the stored execution plans include respective cost parameters representing the hardware capabilities of the system at the time of plan compilation. A set of cost parameters representing the cost of executing the stored execution plan within the database system is compared with the stored cost parameters associated with the retrieved execution plan. On detecting a significant difference between the defined cost parameters and the retrieved cost parameters, the stored execution plan is recompiled.
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