The key index is not strictly
       necessary, but in most scenarios it is helpful.)
       This automatically creates a matching index on each partition, and
       any partitions you create or attach later will also have such an
       index.
       An index or unique constraint declared on a partitioned table
       is <span class="quote">“<span class="quote">virtual</span>”</span> in the same way that the partitioned table
       is: the actual data is in child indexes on the individual partition
 