*
* Takes a list of keys and adds them to the database, merging them with
* the key in the database if it's already present there. The key list is
* update to contain the minimum set of updates required to get from what
* we had before to what we have now (ie the set of data that was added to
* the DB). Returns the number of entirely new keys added.
*
* Takes a list of keys and adds them to the database, merging them with
* the key in the database if it's already present there. The key list is
* update to contain the minimum set of updates required to get from what
* we had before to what we have now (ie the set of data that was added to
* the DB). Returns the number of entirely new keys added.