class ActiveRecord::Batches::BatchEnumerator

def each(&block)

end
relation.update_all(awesome: true)
Person.in_batches.each do |relation|

Yields an ActiveRecord::Relation object for each batch of records. 
def each(&block)
  enum = @relation.to_enum(:in_batches, of: @of, start: @start, finish: @finish, load: false, order: @order, use_ranges: @use_ranges)
  return enum.each(&block) if block_given?
  enum
end