The COMPILE option can be applied to query outlines that have
    been made invalid by DROP TABLE or DROP INDEX. If the tables and
    indices have been recreated then the query outline will be made
    valid again. For example, once re-validated the optimizer will
    try to use that query outline.

                                   NOTE

       There is a possibility that the query outline although
       marked valid will not be used because of changes in the
       index definition. There is too little information stored
       with the query outline to perform a complete consistency
       check. If possible, queries using this outline should be run
       to verify correct index and table usage.

    If the query outline is currently valid then this clause is
    ignored by Oracle Rdb.