ActiveRecord::Batches::BatchEnumerator
Methods
E
Included Modules
Instance Public methods
each()

Yields an ActiveRecord::Relation object for each batch of records.

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

Source: show | on GitHub 

# File activerecord/lib/active_record/relation/batches/batch_enumerator.rb, line 60
def each
  enum = @relation.to_enum(:in_batches, of: @of, start: @start, finish: @finish, load: false)
  return enum.each { |relation| yield relation } if block_given?
  enum
end
each_record()

Looping through a collection of records from the database (using the all method, for example) is very inefficient since it will try to instantiate all the objects at once.

In that case, batch processing methods allow you to work with the records in batches, thereby greatly reducing memory consumption.

Person.in_batches.each_record do |person|
  person.do_awesome_stuff
end

Person.where("age > 21").in_batches(of: 10).each_record do |person|
  person.party_all_night!
end

If you do not provide a block to each_record, it will return an Enumerator for chaining with other methods:

Person.in_batches.each_record.with_index do |person, index|
  person.award_trophy(index + 1)
end

Source: show | on GitHub 

# File activerecord/lib/active_record/relation/batches/batch_enumerator.rb, line 34
def each_record
  return to_enum(:each_record) unless block_given?

  @relation.to_enum(:in_batches, of: @of, start: @start, finish: @finish, load: true).each do |relation|
    relation.records.each { |record| yield record }
  end
end