This is the default behavior for CREATE INDEX. The Oracle Rdb
    optimizer collects approximate cardinality values for the index
    columns to help in future query optimization. Note that no extra
    I/O is incurred to collect these values and, therefore, adjacent
    key values from other index nodes can not be checked. Hence, some
    inaccuracy may be seen for these indexes. In most cases, this
    is adequate for query optimizations. If this clause is used on
    an index that is currently set to PREFIX CARDINALITY COLLECTION
    DISABLED, the RMU Collect Optimizer_Statistics command needs to
    be executed as soon as possible to load the correct values.