Sometimes, we start building content types with cutom fields through the old mighty CCK module, only to find out later that there is a different need or better approach for the specific field and we need to delete and recreate it. This is fine, since we are just in the development mode and i believe it is something that any developer who have used drupal back office faced this akward situation. The question that comes up afterwards it this "How do i clean the deleted file-s from the Database?" We call for once more Drush to the rescue!
$ drush eval "field_purge_batch(500)"
you might have to run a few times, or increase the $batch_size then there might still be field_deleted and field_deleted_revision tables, even after running cron
SELECT * FROM `field_config` WHERE `deleted` = 1
SELECT * FROM `field_config_instance` WHERE `deleted` = 1
if you come up empty, you can safely delete those leftover tables