residual dump files left from 012 migration

we have dump_xyz tables remaining after 012 migration upgrade? do we really need to have a bunch of backup tables to exists post-migration?

explanation from Svetlana:
Guys, my point was:
we had found some of foreign keys declared in models and skipped in database. There was a little chance that we can get a problem in that. If there are some data in table (where foreign key should be declared) that skipped in reference table migration will be failed. We couldn't delete all data in tables that can fail maintain the integrity of reference. So, deleting data in a migration should be done with care, clearly communicated to users, and the data should be logged so that it can be recreated by user if necessary. It was done by backup tables, where all conflicted data were placed.

bug question:
if the integrity of data is invalid should we even keep it? if the foreign key was there from the beginning like it should've been, the unmappable data wouldn't be there to begin with no?

 see: https://bugs.launchpad.net/ceilometer/+bug/1204823