Doing the checksum matching after memory is allocated and all the work is
done is not very efficient. A simpler solution is to always replace the
users when we reload them.
Replacing the users every time the service users are reloaded will not
cause a degradation in performance because the previous implementation
already does all the extra work but then just discards it.
A faster solution would be to first query the server and request some sort
of a checksum based on the result set the users query would
create. Currently, this can be done inside a stored procedure but it is
not very convenient for the average user. Another option would be to
generate a long string with GROUP_CONCAT but it is highly likely that some
internal buffer limit is hit before the complete value is calculated.