# File activerecord/lib/active_record/relation/batches/batch_enumerator.rb, line 25
def batch_size
  @of
end

The size of the batches yielded by the BatchEnumerator.

# File activerecord/lib/active_record/relation/batches/batch_enumerator.rb, line 63
def delete_all
  sum(&:delete_all)
end

Deletes records in batches. Returns the total number of rows affected.

Person.in_batches.delete_all

See Relation#delete_all for details of how each batch is deleted.

# File activerecord/lib/active_record/relation/batches/batch_enumerator.rb, line 83
def destroy_all
  each(&:destroy_all)
end

Destroys records in batches.

Person.where("age < 10").in_batches.destroy_all

See Relation#destroy_all for details of how each batch is destroyed.

# File activerecord/lib/active_record/relation/batches/batch_enumerator.rb, line 92
def each(&block)
  enum = @relation.to_enum(:in_batches, of: @of, start: @start, finish: @finish, load: false)
  return enum.each(&block) if block_given?
  enum
end

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

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

# File activerecord/lib/active_record/relation/batches/batch_enumerator.rb, line 50
def each_record(&block)
  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(&block)
  end
end

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

# File activerecord/lib/active_record/relation/batches/batch_enumerator.rb, line 72
def update_all(updates)
  sum do |relation|
    relation.update_all(updates)
  end
end

Updates records in batches. Returns the total number of rows affected.

Person.in_batches.update_all("age = age + 1")

See Relation#update_all for details of how each batch is updated.