Currently the reindexing mechanism in the GreenHopper ranking field is reindexing all issues which could cause a long waiting period for the user if the project has a big number of issues (in the unscheduled or have at least 1 unreleased version)
The mechanism should be smarter and select just a certain number of issues to be "reflattened" and thus reindexed. This will avoid all issues to be reindexed and greatly ameliorate the waiting experience of the users.