Delete Undefined Mongoid Indexes for Given Model

mongoid_index_cleanup.rb

model = YourModel

current_index_keys = model.collection.indexes.entries.map{|x| x['key'].stringify_keys unless x['key'] == {"_id"=>1}}.compact
defined_index_keys = model.index_options.keys.map{|x| x.stringify_keys}

current_index_keys.each do |k|
  model.collection.indexes.drop(k) unless defined_index_keys.include?(k)
end