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/Ruby on Rails 6.0

class ActiveRecord::Batches::BatchEnumerator

Parent:
Object
Included modules:
Enumerable

Public Instance Methods

each() { |relation| ... } Show source
# File activerecord/lib/active_record/relation/batches/batch_enumerator.rb, line 62
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

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

Person.in_batches.each do |relation|
  relation.update_all(awesome: true)
end
each_record() { |record| ... } Show source
# File activerecord/lib/active_record/relation/batches/batch_enumerator.rb, line 36
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

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

© 2004–2019 David Heinemeier Hansson
Licensed under the MIT License.