Compute the adds and deletes required to get from existing RRData to new RRData
and perform just those operations instead of doing a complete drop/add of the
entire RRData set. Also during an update, do adds before deletes. This
eliminates the existence gap and fixes #29
Compute the adds and deletes required to get from existing RRData to new RRData and perform just those operations instead of doing a complete drop/add of the entire RRData set. Also during an update, do adds before deletes. This eliminates the existence gap and fixes #29