1. A method of selectively recompiling stored execution plans within a database system, the execution plans including respective version numbers of database software operable within the database system during compilation of the respective plans, the method comprising: receiving a request to execute one of the stored execution plans; retrieving the stored execution plan from computer memory; obtaining a version number of database software operable within the database system during retrieval of the stored execution plan; comparing the obtained version number with the version number associated with the retrieved execution plan; and on detecting a mismatch between the obtained version number and the retrieved version number, recompiling the stored execution plan.